UDK:54+66+502/504 ISSN 1840-054X · udk: 54+66+502/504 issn 2232-755x g l a s n i k hemiĈara, tehnologa i ekologa

UDK: 54+66+502/504 ISSN 2232-755X

G L A S N I K HEMIĈARA, TEHNOLOGA I EKOLOGA

REPUBLIKE SRPSKE

Vanredno izdanje

BANJALUKA

BOSNA I HERCEGOVINA

NOVEMBAR, 2016.

Glasnik hem. teh. i ek. RS GHTERS 1-46

UDK: 54+66+502/504 ISSN 2232-755X

G L A S N I K HEMIĈARA, TEHNOLOGA I EKOLOGA

REPUBLIKE SRPSKE

Vanredno izdanje

BANJALUKA

BOSNA I HERCEGOVINA

NOVEMBAR, 2016.

Glasnik hem. teh. i ek. RS GHTERS 1-46

Glasnik hemiĉara, tehnologa i ekologa Republike Srpske Gazette of Chemists, Technologists and Environmentalists of

Republic of Srpska

Izdavaĉ- Publisher Tehnološki fakultet, Univerzitet u Banjaluci

Faculty of Technology, University of Banjaluka

Za izdavaĉa – For Publisher Prof. dr Ljiljana Vukić – Dekan (Dean)

Glavni i odgovorni urednik - Editor-in-Chief Prof. dr Ljiljana Vukić

Gost urednik: Doc. dr Saša Papuga

Sekretar – Secretary Jovanka Todić

Lektor engleskog jezika - Copy editor for English Dr Sanja Josifović-Elezović

MeĊunarodni ureĊivaĉki odbor – International Editorial Board Prof. dr Vlada Veljković, Univerzitet u Nišu, Tehnološki fakultet, Leskovac

Prof. dr Slavko Mentus, Univerzitet u Beogradu, Fakultet za fiziĉku hemiju, Beograd, Prof. dr Sonja Đilas, Univerzitet u Novom Sadu, Tehnološki fakultet, Novi Sad,

Prof. dr Dragoljub Novaković, Univerzitet u Novom Sadu, Fakultet tehniĉkih nauka, Novi Sad Prof. dr Branko Bugarski, Univerzitet u Beogradu, Tehnološko-metalurški fakultet, Beograd

Prof. dr Simona Jevšnik, University of Maribor, Faculty of Mechan. Engineering, Maribor, Slovenia Prof. dr Todor Vasiljević, Victoria University, School of Biomedical and Health Sciences, Melburn, Australia.

Savvas G. Vassiliadis, Piraeus University of Applied Sciences, Technological Education Institute of Piraeus, Athens, Greece

UreĊivaĉki odbor iz BiH - Editorial Board from B&H Dr Branko Škundrić, akademik, Prof. dr Milomir Pavlović, Prof. dr Midhat Jašić, Prof. dr Milorad Maksimović,

Prof. dr Asima Davidović, Prof. dr Zoran Kukrić, Prof. dr Slavica Grujić, Prof. dr Slavica Sladojević, Prof. dr Ljiljana Topalić-Trivunović, Prof. dr Pero Dugić, Prof. dr Snjeţana Mandić, Prof. dr Svjetlana Janjić, Prof. dr Dragana Grujić, Prof. dr Rada Petrović, Prof. dr Branka Rodić-Grabovac, Prof. dr Zora Levi, Prof. dr Biljana Kukavica, Prof. dr Petar

Gvero, Doc. dr Borislav Malinović

Kompjuterska priprema – Computer preparing Branka Ruţiĉić

Tiraţ - Copy 150 primjeraka

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Ul.Vojvode Stepe Stepanovića 73 78 000 Banjaluka

e-mail. [email protected] http://glasnik.tfbl.org

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mailto:[email protected]

http://glasnik.tfbl.org/

This special edition is dedicated to the 11th Symposium of chemists, technologists and environmentalists of Republic of Srpska. It includes plenary lectures and panel sessions lectures.

Editorial Board

Ovaj broj ĉasopisa je posvećen XI Savjetovanju hemiĉara, tehnologa i ekologa Republike Srpske i sadrţi plenarna i sekcijska predavanja

Redakcija

SADRŢAJ TABLE OF CONTENTS

M. Vojinović Miloradov, I. Mihajlović, M. Turk Sekulić, J. Radonić

ENVIRONMENTAL WATERS AND EMERGING SUBSTANCES – STATE OF THE ART AND RESULTS OF TWO INTERNATIONAL PROJECTS

1

M. Sak-Bosnar

PRIMJENA NANOMATERIJALA U KONSTRUKCIJI ELEKTROKEMIJSKIH SENZORA

THE APPLICATION OF NANOMATERIALS IN CONSTRUCTION OF ELECTROCHEMICAL SENSORS

9

A. Orlović, S. Glišić, J. Lukić

TEHNOLOGIJA DEKONTAMINACIJE IZOLACIONIH ULJA KONTAMINIRANIH POLIHLOROVANIM BIFENILIMA

TECHNOLOGY FOR DECONTAMINATION OF INSULATING OILS CONTAMINATED BY POLYCHLORINATED BIPHENYLS

17

D. Savić, B. Danilović, L. Poletto, L. Cocola, M. Fedel

ODREĐIVANJE SADRŢAJA GASA U UPAKOVANIM NAMIRNICAMA BEZ OŠTEĆENJA AMBALAŢE

GAS CONTENT MEASUREMENT IN HEADSPACE OF FOOD PACKAGES ON NON-DESTRUCTIVE MANNER

25

N. Kašiković, G. Vladić, D. Novaković

ŠTAMPA NA TEKSTILU – PROŠLOST, SADAŠNJOST, BUDUĆNOST

TEXTILE PRINTING – PAST, PRESENT, FUTURE

35

PLENARY LECTURES

PLENARNA PREDAVANJA

Glasnik hemiĉara, tehnologa i ekologa Republike Srpske, (2016) 1-6, - Vanredno izdanje -

1

ENVIRONMENTAL WATERS AND EMERGING SUBSTANCES – STATE OF THE ART AND RESULTS OF TWO INTERNATIONAL PROJECTS

Mirjana Vojinović Miloradov, Ivana Mihajlović, Maja Turk Sekulić, Jelena Radonić,

University of Novi Sad, Faculty of Technical Sciences, Department of Environmental Engineering and Occupational Safety and Health, Trg Dositeja Obradovića 6, Novi Sad

ISSN 2232-755X UDC: 628.3.034.2:637.1

DOI: 10.7251GHTE16VI001

Environmental waters are generally natural recipients of industrial and communal wastewaters by which emerging substances are inputted in and caused contamination. Environmental waters include surface water of river, lake, and other water bodies which are open for all types of effluents and constantly replenished by different organic and inorganic loads. Emerging substances are the old compounds, pollutants and chemicals, but newly recognized and for which regular monitoring and maximum allowable concentrations are not defined in European Union as well as in developing countries as it is Serbia, Bosnia and Herzegovina and others. NORMAN is the official website with open and dynamic list on which after the prioritisation process new members of emerging substances are included in. Within NATO project four screening and two target analyses of Danube surface water and wastewater in the vicinity of Novi Sad were performed. More than 150 compounds were detected in screening analyses and from 82 target organic compounds 19 were measured above limits of detection. Based on evaluation of results obtained within two international Projects specific and unique physicochemical characteristics of emerging substances were observed, such as low and sub-low concentrations, non-monotonic dose response, effects of chemical cocktails, pseudopersistency, interreaction with proteins and toxicity with acute, but rather chronic consequence.

Key words: emerging pollutants, Danube surface water, wastewater.

INTRODUCTION

Mysterious emerging substances (EmS) are present in waste, as well as in surface and receiving water bodies [1, 2]. The most common mechanism for EmS is input into the environment through the wastewater discharges, application of sewage sludge, landfill leachate, accidents and other ways.

NORMAN (Network Laboratories Monitoring of Emerging Pollutants) has established a list of the currently most frequently detected and analyzed EmS today. It consists of 25 different classes of pollutants with more than 1000 individual substances with CAS (Chemical Abstracts Service) [3]. EmS do not have proper regulatory approach for detection and defined maximum allowable concentrations, since their concentrations are often very low, in range of nano to pico molar and require new methods of determination and high sophisticated instrumental analytical equipment. EmS have the exceptional and new properties such as pseudoperesistence, inertness and stability with certain ecotoxicological effect and special effect of chemical cocktails and possible chemical forms in aquatic bodies.

EmS are ubiquitous, persistent/pseudo-persistent and biologically active molecules that occur in the environment as a result of natural, industrial and human activities. The dominant physicochemical characteristics particularly specific for EmS are: stable structure, low/non degradability, hydrophilicity and lipophilicity, bioconcentration/bioaccumulation and interaction with proteins, toxicity, acute, but rather toxic chronic effect. Low doses effect with non-monotonic response and toxic effects are observed in the picomolar to nanomolar range with new ecotoxicological impacts. EmS are volatile/non/semi volatile compounds, polar/nonpolar molecules, with short half-lives. Their main physical and chemical properties are characterized by experimentally or mathematically derived constants of: protonation (Log pKa ) in range of 9.6 – 2.5, octanol–water partition coefficient (Log Kow) in range 0.35 – 9.2 and solubility (Sw) in range from 1*106 mg/l to 0.02 mg/l [4]. Chemical forms of EmS in aquatic media could be in molecular, ionic (cationic/anionic) and

zwiter ions modality. For most EmS, there is currently little information about their potential toxicological consequences on ecosystems, particularly from long-term low-level environmental exposure.

M. Vojinović Miloradov i sar.: ENVIRONMENTAL WATERS AND EMERGING SUBSTANCES...

2

Table 1. Physico-chemical properties of selected EmS (some NSAID and antibiotics), shortened list [5]

Pharmaceutical pKa Log Kow

Sw 25ºC

(mg l-1)

Log Kd Charge

at pH 7 Molecular structure

An

alg

esic

s/A

nti

-

infl

am

ma

tori

es

Diclofenac

CAS # 15307-86-5

4.15 4.51/0.7 4.52 1.2 Negative

An

alg

esic

s/A

nti

-in

fla

mm

ato

rie

s

Ibuprofen

CAS # 15687-27-1

4.51 3.97/0.45 41.05 0.9 Negative

Ketoprofen

CAS # 22071-15-4

4.45 3.12/-0.44 120.4 1.2 Negative

Ketorolac

CAS # 74103-06-3

2.32 572.3 Negative

Naproxen

CAS # 22204-53-1

4.2 3.18/-0.34 144.9 1.1 Negative

An

alg

esic

s/A

nti

-

infl

am

ma

tori

es

Salicylic acid

CAS # 69-72-7

3.5 2.26/-2.42 3808 Negative

An

tib

ioti

cs

Amoxicillin

CAS # 26787-78-0

2.4 0.87 3433 Neu./Neg

.


3

Pharmaceutical pKa Log Kow

Sw 25ºC

(mg l-1)

Log Kd Charge

at pH 7 Molecular structure

An

tib

ioti

cs

Ciprofloxacin

CAS # 85721-33-1

6.38 0.4 1.148 104 4.3 Pos./Neu.

An

tib

ioti

cs

Doxycycline

CAS # 564-25-0

pK1= 3.5

pK2= 7.7

pK3= 9.5

-0.02 312.9

Erythromycin

CAS # 114-07-8

8.8-8.9 3.06 0.5168 2.2 Positive

An

tib

ioti

cs

Lincomycin

CAS # 154-21-2

0.29 92.19 Pos./Neu.

Ecoological characteristics of EmS couldn‘t be defined on the basis on mono form of analyte, because EmS in environment are present in the chemical cocktail, CC, which is characterized by complex phenomena such as synergistic, antagonistic and catalytic interactions. The components of chemical cocktails complicate the explanation of

toxicological effects between at the same time presents EmS and other chemicals in biological fluids. Every day, the cells are exposed to a large number of emerging chemicals, coming from many different sources: pharmaceuticals, personal care products, toys, cosmetics, electronic equipment, indoor air, dust, additives, food and many others which are the components of the chemical mixture and material of everyday life.

EmS which are constantly released to aquatic environment are attributed as pseudo–persistent even if their half-lives are short. Pseudo–persistency is the consequence of the constant supply of EmS which are continually refilled and reloaded on environment, especially in aquatic media, i.e. receiving water.

Toxic effects of EmS in very low doses in continuum functioning and the phenomena of pseudo-persistency are particularly important for continual, multigenerational exposure of aquatic organisms to these hazardous species.


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Thermodynamic kinetic equilibrium processes within domain of pseudo persistency phenomena could be presented by mathematical relation in which the rate of input of EmS (vin), [mol L-1 s-1] is significantly higher than the rate of output (vout), [mol L-1 s-1]

vin>>vout (1)

that means that the molar concentrations of EmS which is released in the surface water are much higher than the residues of concentrations after the sum of EmS degradation processes, i.e. concentration of influent > effluent

Cin>>Cout [mol L-1] (2) Actually, the rate of input (release, emission, generation) of EmS into receiving water is much higher than the rate of output. The kinetic rate of different physicochemical and biological degradation processes, transformation and mineralization processes of EmS are very slow. EmS generally have short half-lives, t½, but they may be able to cause the same exposure potential and toxic effect as persistent pollutants, since their transformation and removal rates can be compensated by their continues input into environment/receiving water. According to this, EmS are attributed as pseudo persistent chemicals. Three screening campaigns in the river Danube in the vicinity of Novi Sad have been performed within the NATO Project ESP.EAP.SFP 984087 in order to determine occurrence of EmS, priority and hazardous substances of interest for Danube basin and to proceed and conduct with target analysis of Danube surface water and wastewater discharged directly into Danube, which is the fundamental basis for the broader knowledge of the newly properties of EmS.

MATERIAL AND METHODS OF WORK

The City of Novi Sad with 350,000 inhabitants has joint collector for both industrial and municipal wasterwater, directly discharged into Danube. Based on the location of the entire sewerage network in the City and previous analysis, 11 sampling points have been selected for the investigations. Five sites were located in the Danube's riverbed, four were in municipal wastewater collectors, while one presented raw water used for drinking water production (Figure 1).

Figure 1. Sampling locations for screening and target analysis

All samples were collected in plastic and glass bottles and stored at 4°C until analysis. A 800 ml aliquot of water sample were spiked with internal standard (phenanthrene-D10 in case of PAHs and industrial chemicals andpropazine or cis-chlordane in case of pesticides and mass labeled PBDE-138 -Wellington laboratories) to achieve final concentration of 1μg/l and extracted with two 50 ml portions of dichloromethane for 20 minutes. After extraction, both extracts were combined and dried with anhydrous sodium sulfate. The combined extract after filtration was evaporated using Kuderna-Danish apparatus to final volume of 1 ml. A 50 μl of extract was injected into Agilent 6890 GC with Agilent 5973 MS detector. The GC system was equipped with PTV injector that was programmed from 60 °C to 260 °C (5 minutes) at a rate of 40 °C/min. Capillary GC analysis was performed on a 30 m x 250 mm I.D., 0.25 mm df DB-XLB and HP-5MS column. Helium was used as carrier gas. The MSD was used in SIM mode for all samples. Each target compound was qualified by two qualifier ions and quantified by one specific or base ion. Screening and target analysis have been conducted in the laboratories of the Slovak University of Technology in Bratislava.


5

RESULTS AND DISCUSSION

The most frequently compounds occurring in studied water samples were phthalates, PAHs, terpenes and fatty acids. Special groups detected in all waste and river water samples were terpenes like nerol, citronellol, menthol, ionone and other compounds like camphor, ethyl citrate or methyl jasmonate that could occur in cosmetics, care products, and home cleaning products. Wide variety of hormones, derivatives of benzene and polycyclic aromatic hydrocarbons (PAHs) were detected in many studied water samples. The risk assessment analysis was performed based identification of the extent of exceedance of ecotoxicity thresholds, PNEC values and data obtained from target and screening analytical results. The most accurate PNEC values were already defined in the existing EU legislation, while for other compounds they were either identified in the ecotoxicity databases or estimated by evaluation of QSAR data of certain compound for fish (Pimephales promelas), Daphnia magna and algae (Selenastrum capricornutum). Prioritization based on occurrence (maximum environmental concentration - MEC) and predicted toxicity data (predicted no effect concentrations - PNEC) has been conducted in order to generate the list of priority substances relevant for the water-monitoring network in the city of Novi Sad. Based on the proces of prioritization the first list in Serbia of 300 relevant organic and inorganic compounds was prepared and represent a potential threat for contamination of raw water used for preparation of drinking water.

Table 2. MEC/PNEC ratio of emerging and priority substances in water samples [6]

Compound name Wastewater Compound name Surface water Compound name Raw water

Heptachlor 2100000 Heptachlor 350000 DDD-4,4' 9

Benzo(a)anthracene 117 Heptachlor epoxide 250000 PCB-194 5

Fluoranthene 81 DDT-4,4' 50 DDE-4,4' 3

Endosulfan-alpha 46 Chlorpyrifos 40 Hexachlorobenzene 3

DDT-4,4' 31 DDD-4,4' 25 Pentachlorobenzene 2

Dieldrin 27 Endosulfan-alpha 12 1,2-benzenedicarboxylic acid, dibutyl ester

2

Target analysis points out on high concentration levels of pesticides and PAHs in the wastewater samples. Analysis of Danube water samples shows high concentration of pesticides, which persist even in surface water after sewerage system discharge locations, while PAHs are either diluted or sorbed to sediment. Group of phthalates, represented by dibutyl phthalate was detected in both wastewater and surface water. Raw water contains only pesticides DDD and DDE, dibutyl phthalate, PCB-194, as well as hexachlorobenzene and pentachlorobenzene. All compounds detected in raw water, have also been detected in wastewater and surface water, and therefore it can be concluded that they are major source of pollution in raw water, and not the groundwater coming from hinterland. Concentration level of DDD-4,4‘ has been reduced from wastewater to raw water, while other compounds remained with the same MEC/PNEC ratio throughout all water sources.

In general, majority of compounds that appear in surface water are also present in raw water, with alkanes as predominant pollutants. Similar trend has been spotted for hexacosane, pentacosane and tetracosane, where their

ratio has been amplified in surface water, and then significantly reduced in raw water. Concentration level of heptacosane was reduced 3 times from wastewater to surface water, and further reduction was observed in raw water, while concentration of docosane and 3-methyl heneicosane, has even amplified about 8 times from surface water to raw water, indicating possible pollution from hinterland.

CONCLUSIONS

EmS are pollutants with growing concern of their occurrence in environment, toxic effect, distribution, transport and fate with relatively low concentrations in wastewater, low and sub-low concentrations in surface water, groundwater or raw water as well as drinking water resources with possible negative effects on humans and aquatic ecosystem. The research progress has been made regarding the new information, data monitoring and knowledge of the specific physico-chemical characteristic as the low doses effects, NMDR, pseudo-persistence, unknown toxic effect of alone


6

emerging chemical in chemical cocktail and suspected carcinogenic and teratogenic effects of some EmS. These new statements require the shifting in a concept of the whole environmental protection. Based on results obtained within NATO and NETREL Projects, the list of 300 relevant organic and inorganic compounds was established, which represent a potential threat for contamination of raw water used for preparation of drinking water. Obtained list served as input data for the establishment of standard operating procedure within the Novi Sad municipality and assessment of risk for relevant detected pollutants. Implementation of joint risk management plans and strategies against hazards, which might be caused by the emerging chemical substances in surface and raw water, could serve as an example for other cities with similar drinking water production in Serbia as well as in surrounding countries. Based on the results of the level concentrations of EmS detected in surface water and wastewater, there is approval of correlation in the line wastewater-surface water and raw water. This correlation points out that the treatment of wastewater is extraordinary important, since wastewater is the main source of contamination of surface water, the wells in Danube alluvium in the vicinity of Novi Sad and raw water. Presented study of the wastewater and surface water quality was performed for the first time in Novi Sad and its surroundings, where municipal and industrial wastewaters are directly discharged, without any treatment, into the Danube River. Acknowledgement: The research is supported by NATO Project DriWaQ-NS (ESP.EAP.SFP 984087) and project of the Ministry of Education, Science and Technological Development (III46009).

LITERATURE

1. Grujić Letić, N., Milić, N., Turk Sekulić, M., Radonić, J., Milanović, M., Mhajlović, I., Vojinović-Miloradov, M. Quantification of emerging organic contaminants in the Danube River samples by HPLC, Chemicke Listy, 106 (2012), 264-266.

2. Milić, N., Milanović, M., Grujić Letić, N., Turk Sekulić, M., Radonić, J., Mihajlović, I., Vojinović Miloradov, M. Occurrence of antibiotics as emerging contaminant substances in aquatic environment. Int J Environ Health Res. 23 (4) (2013), 296-310.

3. NORMAN, http://www.norman-network.net/index_php.php.

4. Vojinović Miloradov, M., Turk Sekulić, M., Radonić, J., Milić, N., Grujić Letić N., Mihajlović, I., Milanović, M. Industrial emerging chemicals in the environment. Hem. Ind. 68 (1) (2014) 51–62.

5. Vojinović Miloradov, M., Špánik, I., Turk Sekulić, M., Radonić, J., Vyviurska, O., Mihajlović, I. Occurrence, Physico–Chemical Characteristics and Analytical Determination of Emerging Substances, Faculty of Technical Sciences, Serbia, December 2016.

6. Vojinović Miloradov. M., Mihajlović, I., Vyviurska, O., Cacho, F., Radonić, J., Milić, N., Spanik, I. Impact of wastewater discharges to Danube surface water pollution by emerging and priority pollutants in the vicinity of Novi Sad, Serbia. Fresenius Environmental Bulletin 23 (9) (2014) 2137-2145.

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PANEL SESSIONS LECTURES

SEKCIJSKA PREDAVANJA


9

THE APPLICATION OF NANOMATERIALS IN CONSTRUCTION OF ELECTROCHEMICAL SENSORS

Milan Sak-Bosnar

Department of Chemistry, Josip Juraj Strossmayer University of Osijek

ISSN 2232-755X UDC: 543.554.4-32:615.212.033

DOI: 10.7251GHTE16VI009B

MWCNT was used as a conducting substrate at construction of an all solid contact anionic surfactant sensor which used 1,3-didecyl-2-methylimidazolium-tetraphenylborate (DMI-TPB) ion pair as the sensing element implemented in PVC membrane. SEM was used for morphological characterization of the sensor. The detection limits for DS and DBS were 1,2 x 10-7 and 2,6 x 10-7 M, respectively. The sensor revealed a stable potentiometric response in a pH range between 3 and 13 with a signal drift of 1,9 mV/hour, and exhibited outstanding selectivity performances for DS toward the majority of organic and inorganic anions most frequently employed in commercial formulations based on surfactants. The new sensor was applied for the end-point location at potentiometric anionic surfactant titrations. The sensor was tested at determination of ASs in commercial detergent products and the results were compared with those obtained with the standard two-phase titration method exhibiting the satisfactory mutual agreement.

Keywords: surfactant sensor, MWCNT, anionic surfactant, potentiometric titration.

INTRODUCTION

In recent years, nanomaterials (NMs) were gradually introduced into potentiometric sensors too. The exceptional electrical properties and good hydrophobicities of nanomaterials make them suitable as solid contacts for solid-state sensors. The immobilization of the ionophore on nanomaterials not only eliminates its leaching from the ion-selective membrane, but also develops an alternative sensing membrane. Also, potentiometric sensors with new sensing concepts have been developed based on the functionalization of nanomaterials with receptors.

It can be concluded that the introduction of NMs enables the development of a new type of potentiometric sensors in which the polymeric membrane has been replaced by receptors linked directly to the transducers. Besides, the

functionalization of NMs offers the possibility of directly linking the receptor molecules to NMs instead of entrapping them in the ion-selective polymeric membranes.

The existing methodology for the monitoring of surfactants in industrial products and effluents is based on the time-consuming extraction-spectrophotometric procedures connected with numerous drawbacks: considerable chemicals consumption, use and disposal of toxic organic solvents, the difficulty of determination in turbid or colored samples, subjectivity, the lack of automatization, and the existence of many sources of interference [1, 2].

Potentiometric methods with surfactant sensors (surfactant-selective electrodes) sensitive to the surfactants overcome most of the above disadvantages offering an attractive alternative to the existing methods [3-11].

The biggest challenge in potentiometric surfactant analysis is the determination of low levels in environmental samples [12-14].

ISE incorporated into a flow injection analysis system (FIA) can also be used for the analysis of low levels of AS [15, 16]. Although surfactant sensors represent a great progress in surfactant analysis, they suffer of the following drawbacks: leaching of the membrane components, extraction of lipophilic molecules into the polymeric membrane, limited life (operating) time, use of internal (filling) solution, poor mechanical properties, low resistance to organic solvents, slow response at some types of sensors.

The use of NMs in potentiometric surfactant sensors development may contribute to overcoming of most of the drawbacks of liquid membrane type surfactant sensors. It will provide a new insight to the understanding of the new response mechanisms of the sensor at the interface surfactant ion in solution and NM-based sensing membrane.

Until now, there are only two publications related to the application of NMs in surfactant sensors [17, 18].

In this paper MWCNT was used as a conducting substrate at preparation of an all solid contact anionic surfactant sensor (NMSS) based on 1,3-didecyl-2-methylimidazolium-tetraphenylborate (DMI-TPB) ion pair as an ionophore implemented in PVC membrane.

M. Sak-Bosnar: THE APPLICATION OF NANOMATERIALS IN CONSTRUCTION OF ELECTROCHEMICAL SENSORS

10

MATERIAL AND METHODS OF WORK

Material for MWCNT-based surfactant sensor (NMSS)

The NMSS membrane was fabricated on leads pencil graphite, HB with 2 mm diameter (Faber-Castell, Germany). Two component epoxy (Pattex, Germany) was used as an insulator for the leads pencil graphite. Chemicals for sensing leyers (Layer 1 and Layer 2) preparation were low ohm carbon ink (CI) with electrical resistance <10 Ohms (ECM, USA), multi walled carbon nanotubes (MWCNT) with diameter 10-20 nm and 2 μm length (IoLiTec Nanomaterials, Germnay), 1,3-didecyl-2-methylimidazolium chloride (DMIC) and sodium tetraphenylborate (TPB) were used for the 1,3-didecyl-2-methylimidazolium- tetraphenylborate (DMI-TPB) ionophore synthesis (all from Sigma Aldrich, Germany). Dimethylformamide (DMF), tetrahydrofuran (THF), ortho-nitrophenyl octyl ether (o-NPOE), high molecular weight PVC (all from Fluka, Switzerland), and dichloromethane (Kemika, Croatia) were used too. All solutions were prepared in high purity water from a TKA, GenPure Ultra Pure Water System (TKA, Niederelbert, Germany), resistivity greater than or equal to 18 MΩ cm.

The response characteristics of the NMSS were investigated using dodecyl sulphate (DS) and dodecylbenzenesulphonate (DBS) in deionised water (all from Fluka, Switzerland). DS was used for potentiometric titrations with hexadecyltrimethylammonium bromide (CTAB, Sigma Aldrich, Germany).

Preparing of the NMSS membrane

Layer 1 cocktail

The MWCNT disperision was prepared by its ultrasonification in DMF (3 mg/mL) for 10 minutes. Next, dispersion was added to CI and mixed to the final concentration of 0,1 %. Freshly prepared layer 1 cocktail was ready for use.

Layer 2 cocktail

The DMI-TPB ion-pair was prepared by dissolving equimolar amounts od DMIC and TPB in dichloromethane, forming a sparingly soluble precipitate. The precipitate was extracted, recrystallysed and purified. The newly synthetised ion-pair was used as a sensing material for the preparation of the layer 2 - PVC-based membranes plasticized with o-NPOE.

Preparation of the NMSS sensor

A pencil-graphite electrode was insulated using epoxy resin. After drying, the top surface of the electrode was polished with emery paper. The electrode was ready for sensor preparation.

For the preparation of the NMSS the layer 1 cocktail containing MWCNT was dropcasted onto the polished top surface of the electrode. After drying for 12 hours at room temperature the layer 2 cocktail containing surfactant sensitive ion-pair DMI-TPB was dropcasted onto the layer 1 surface and dried for another 12 hours at room temperature before measurement. The design of the NMSS was shown in Figure 1.

Figure.1. Design of the two-layer NMSS sensor

Apparatus

The potentiometric titrations were carried out using an all-purpose titrator, 808 Titrando (Metrohm, Switzerland), combined with a Metrohm 806 Exchange unit (Metrohm, Switzerland) controlled by the Tiamo software (Metrohm, Switzerland). Sonoplus Ultrasonic homogenizer with a horn sonicator HD 3100 (both from Bandelin, Germany) was used for cocktails preparation. Electrochemical impedance spectroscopy (EIS) measurements were performed by using an CH Instruments Electrochemical Analyser (model 600E series, CH Instruments, Austin, USA) connected to a three-electrode electrochemical cell.


11

Procedure

A NMSS, made from two layers (MWCNT/CI/ionophore layer 1 and ionophore-PVC layer 2), was used for all potentiometric measurements. Silver/silver chloride electrode was used as the reference. The volume of the solution used for the titrations was 25 mL and for the response measurements was 20 mL.

Response measurements

The investigation of the NMSS response to DS and DBS was accomplished by incremental addition of the solution of corresponding anionic surfactant to deionized water and to sodium sulfate (c = 10 mM) solution. The investigated concentrations of DS and DBS were 5 x 10-4 M and 5 x 10-5 M.

Potentiometric titration

The solution of CTAB (c = 4 x 10-3 M), was used as the titrant, while DS was used as analyte during the potentiometric titrations. The volume of the solution used for all of the titrations was 25 mL. The standard addition method in which DS was added at two concentration levels was used for the determination of the accuracy and precision of the measurements.

RESULTS AND DISCUSSION

Response characteristics

The titration of ionic surfactants is based on the reaction of two oppositely charged large organic or inorganic ions (both with lipophilic character) resulting in the formation of a sparingly soluble compound (ion-pair, ion-associate):

(1)

The potentiometric sensors incorporating an ion-pair CA can be used for ionic surfactant determination.

The electrode potential E of such a sensor responding to surfactant anion A- is described by the Nernst equation:

E = E0 – S x log ɑA- (2), where

E0 = constant potential term, S = sensor slope, which for monovalent ion amounts is 59.2 mV/decade of activity ɑA- = activity of the surfactant anion.

The response characteristics of the new potentiometric sensor (NMSS) were investigated in solutions of the two most frequently used anionic surfactants sodium dodecyl sulfate (NaDS) and sodium dodecylbenzenesulfonate (NaDBS) and

are shown in Figure 2.

Figure.2. Responses of the NMSS to DS and DBS in water and in 10 mM Na2SO4. Here and in further figures, some

curves are displaced laterally and/or vertically for clarity


12

The sensor response characteristics, based on a series of five measurements, were evaluated by using linear regression analysis (Table 1).

Table 1. Statistics of the response characteristics of the NMSS sensor to DS and DBS, given together with ±95 % confidence limits

Parameters NaDS in H2O NaDS in Na2SO4

0,01 M NaDBS in H2O

NaDBS in Na2SO4 0,01 M

Slope / (mV/decade of activity)

55,3 ± 0,9 55,4 ± 0,5 58,5 ± 1,7 57,7 ± 1,4

Intercept (mV) -338,3 -322,0 -365,9 -353,3

Standard error 1,9 1,9 5,4 2,9

Correl. coeff. (R2) 0,9987 0,9993 0,9940 0,9970

Detection limit (M) 2,5 x 10-7 2,5 x 10-7 2,0 x 10-7 1,2 x 10-7

Useful conc. range (M) 3,2 x 10-7 – 4,6 x 10-3

2,5 x 10-7 – 4,6 x 10-3

2,5 x 10-7 – 1,2 x 10-3

1,5 x 10-7 – 8,8 x 10-4

SEM characterization of the NMSS sensor

Carbon nanotube suspension and the new NMSS were characterised by scanning electron microscopy (SEM), on a Tescan Vega3 electron microscope operating at 20 kV (Figure 3).

Figures 3 (A) and 3 (B) show the surface of the NMSS taken at lower (A) and higher (B) magnification. Occasionally larger agglomerates are visible, but the majority of nanotubes are homogenously distributed through the film, forming smaller agglomerates several micrometres in diameter which are completely covered by the polymer.

Figure A Figure B

Figure.3. SEM image of the NMSS at lower (A) and higher (B) magnification


13

Titration of commercial products

The determination of ASs in different formulated products on surfactant basis (household products, industrial detergents, cosmetics, etc.) belongs to the main use of surfactant potentiometric sensors.

For this purpose the two commercial products (laundry detergent in gel form, liquid hand-dishwashing detergent) were titrated with standard solution of CTAB (c = 4 x 10-3 M) as the titrant (Figure 4). The new NMSS sensor was used as an end-point indicator. The accuracy and precision of the determination as well as the influence of the matrix, were tested with the known addition method by addition of the known volumes of standard solution of NaDS to the products investigated.

The results and related statistics of the determination of ASs in the products investigated are given in Table 2.

Figure.4. Titration curves of two commercial detergents and with the addition of known amounts of DS (c = 1 x 10-4

M) obtained by using 0,1 mM CTAB as the titrant and the new NMSS sensor as an end-point detector (○ sample 1, ●

sample 1 + 2 mL DS, Δ sample 2, ▲ sample 2 + 2 mL DS)

Table 1. Statistics of the response characteristics of the NMSS sensor to DS and DBS, given together with ±95 % confidence limits

Detergent type

NaDS

AS found (M) Added (mol) Found (mol) Recovery

(%)

Gel detergent 6,53 x 10-4 8 x 10-6 8,09 x 10-6 101,1

Liquid hand-dishwashing detergent 2,21 x 10-3 8 x 10-6 7,97 x 10-6 99,7

*waverage of 5 determinations


14

CONCLUSIONS

MWCNT was used as a conducting substrate at preparation of an all solid contact anionic surfactant sensor (NMSS) based on 1,3-didecyl-2-methylimidazolium-tetraphenylborate (DMI-TPB) ion pair as an ionophore implemented in PVC membrane. The sensor exhibited high sensitivity and fast response to DS and DBS and demonstrated excellent selectivity for DS toward the most organic and inorganic anions commonly employed in commercial product formulations containing surfactants. Its main use is in end-point detection at the ionic surfactant potentiometric titrations. The obtained titration curves evidenced clearly defined inflexions ensuring the reliable end-point location by using of CTAB as a standard cationic titrant. The two commercial detergents of different formulation complexity were tested. The results were compared to those obtained with the standard two-phase titration method, and they exhibited satisfactory mutual agreement.

Acknowledgements

This work has been supported by the Croatian Science Foundation under the project IP-11-2013.

LITERATURE

1. ISO 2271:1989 Surface active agents - Detergents - Determination of anionic-active matter by manual or mechanical direct two-phase titration procedure, International Organization for Standardization, Geneva, Switzerland.

2. ISO 7875-1:1996 Water quality - Determination of surfactants - Part 1: Determination of anionic surfactants by measurement of the methylene blue index (MBAS) International Organization for Standardization, Geneva, Switzerland.

3. Kovács, B. Csóka, B., Nagy, G., Ivaska, A., All-solid-state surfactant sensing electrode using conductive polymer as internal electric contact. Anal. Chim. Acta, 437 (2001), 67–76.

4. Masadome, T., Yang, J.G., Imato, T., Effect of plasticizer on the performance of the surfactant-selective electrode based on a poly(vinyl chloride) membrane with no added ion-exchanger. Microchim. Acta 144 (2004) 217–220.

5. Karami, H., Mousavi, M.F., Dodecyl benzene sulfonate anion-selective electrode based on polyaniline-coated electrode. Talanta 63 (2004) 743–749.

6. Varga, I., Meszaros, R., Szakacs, Z., Gilanyi, T., Novel method for the preparation of anionic surfactant-selective electrodes. Langmuir 21 (2005) 6154–6156.

7. Segui, M.J., Lizondo-Sabater, J., Benito, A., Martinez-Manez, R., Pardo, T., Sancenon, F., Soto, J., A new ion-

selective electrode for anionic surfactants. Talanta 71 (2007) 333–338. 8. Madunić-Ĉaĉić, D., Sak-Bosnar, M., Matešić-Puaĉ, R., Grabarić, Z., Determination of anionic surfactants in real

systems using 1,3-didecyl-2-methyl-imidazolium-tetraphenylborate as sensing material. Sens. Lett. 6 (2008) 339–346.

9. Khaled, E., Mohamed, G.G., Awad, T., Disposal screen-printed carbon paste electrodes for the potentiometric titration of surfactants. Sens. Actuat. B 135 (2008) 74–80.

10. Madunić-Ĉaĉić, D., Sak-Bosnar, M., Galović, O., Sakaĉ, N., Matešić-Puaĉ, R., Determination of cationic surfactants in pharmaceutical disinfectants using a new sensitive potentiometric sensor. Talanta 76 (2008) 259-264.

11. Madunić-Ĉaĉić, D., Sak-Bosnar, M., Matešić-Puaĉ, R., A new anionic surfactant-sensitive potentiometric sensor with a highly lipophilic electroactive material. Int. J. Electrochem. Sci. 6 (2011) 240-253.

12. Madunić-Ĉaĉić, D., Sak-Bosnar, M., Samardţić, M., Grabarić, Z., Determination of anionic surfactants in industrial effluents using a new highly sensitive surfactant-selective sensor. Sens. Lett. 7 (2009) 50–56.

13. Galović, O., Samardţić, M., Dereţić, D., Madunić-Ĉaĉić, D., Sak-Bosnar, M., Potentiometric titration of micromolar levels of anionic surfactants in model effluents using a sensitive potentiometric sensor. Int. J. Electrochem. Sci. 7 (2012) 1522-1531.

14. Galović, O., Samardţić, M., Petrušić, S., Sak-Bosnar, M., Application of a new potentiometric sensor for determination of anionic surfactants in wastewater.

Chem. Biochem. Eng. Q., 29 (2015) 307-313 15. Martínez-Barrachina, S., Alonso, J., Matia, L., Prats, R., del Valle, M., Determination of trace levels of anionic

surfactants in river water and wastewater by a Flow Injection Analysis system with on-line preconcentration and potentiometric detection. Anal. Chem. 71 (1999) 3684–3691.

16. Masadome, T., Kugoh, S., Ishikawa, M., Kawano, E., Wakida, S., Polymer chip incorporated with anionic surfactant-ISFET for microflow analysis of anionic surfactants. Sens. Actuat. B 108 (2005) 888–892.

17. Mojgan, N., Maleki, L., Rafati, A.A., Novel surfactant selective electrochemical sensors based on single walled carbon nanotubes. J. Mol. Liq. 159 (2011) 226-229.


15

PRIMJENA NANOMATERIJALA U KONSTRUKCIJI ELEKTROKEMIJSKIH SENZORA

Milan Sak-Bosnar

Odjel za kemiju, Sveuĉilište Josipa Jurja Strossmayera u Osijeku

Nanomaterijali (NM) se široko primjenjuju pri izradi razliĉitih kemijskih senzora i biosenzora zbog svojih jedinstvenih fizikalnih i kemijskih svojstava, kao što su omjer izmeĊu velike specifiĉne površine i zapremine, dobra elektriĉna provodnost, izuzetna elektrokatalitiĉka aktivnost i velika mehaniĉka ĉvrstoća. Pri razvoju elektrokemijskih senzora NM se mogu ispitivati kao vodljivi supstrati (ĉvrsti kontakti), kao supstrati za imobilizaciju elektroaktivnog materijala i kao potencijalni senzorski materijali nakon njihovog funkcionaliziranja (funkcionalizirani nanomaterijali, FNM). Upotreba NM prikazana je na razvoju, konstrukciji i primjeni nekoliko tenzidskih potenciometrijskih senzora korištenjem grafena, jednostjenĉanih ugljikovih nanocjevĉica (SWCNT) i višestjenĉanih ugljikovih nanocjevĉica (MWCNT), za imobilizaciju senzorskog materijala u membrani u cilju sprijeĉavanja njegovog ispiranja iz membrane, kao i za smanjenje elektriĉnog otpora i šuma signala membrane. Novi senzori na bazi NM primijenjeni su za odreĊivanje anionskih tenzida u komercijalnim proizvodima i otpadnim vodama, a rezultati su usporeĊeni s rezultatima dobivenim konvencionalnim potenciometrijskim senzorima kao i standardnim metodama. Novi se senzori mogu lako minijaturizirati (nema unutrašnje otopine za punjenje, bolje mehaniĉke osobine i dr.).

Kljuĉne rijeĉi: nanomaterijal, elektrokemijski senzor, potenciometrijski senzor, tenzid


17

TEHNOLOGIJA DEKONTAMINACIJE IZOLACIONIH ULJA KONTAMINIRANIH POLIHLOROVANIM BIFENILIMA

Aleksandar Orlović1, Sandra Glišić1, Jelena Lukić2

1Tehnološko-metalurški fakultet Univerzitet u Beogradu, Karnegijeva 4, Beograd, Republika Srbija, [email protected]

2Elektrotehniĉki institut „Nikola Tesla‖, Koste Glavinića 8a, Beograd, Republika Srbija, [email protected]

ISSN 2232-755X UDC: 614.878:547.622

DOI: 10.7251GHTE16VI017O

Zakon o zaštiti ţivotne sredine nalaţe vlasnicima elektroenergetske opreme punjene uljima da ispitaju, oznaĉe i deklarišu opremu koja je kontaminirana polihlorovanim bifenilima (PCB). Eksploatacija PCB kontaminiranih transformatora povezana je sa rizicima od emisija PCB-a u ţivotnu sredinu i prodor u lanac ishrane, rizicima od havarija transformatora usled neispravnog pogonskog stanja i mogućeg masovnog izlivanja ulja i PCB-a u okolinu, paljenja ulja i nepotpunog sagorevanja, te stvaranja veoma toksiĉnih jednjenja, što u krajnjoj instanci moţe dovesti do ozbiljnih ekoloških incidenata. Jedan od naĉina rešavanja problema eksploatacije PCB kontaminiranih transformatora, ĉiji je nastavak eksploatacije neophodan ili poţeljan, je primena postupaka dekontaminacije. U radu su prikazani rezultati primene procesa dekontaminacije ureĊaja kontaminiranih PCB-om postupkom dehlorinacije. Izvedene su dekontaminacije ureĊaja u Republici Srbiji u okviru preduzeća JP EMS i JP EPS. Transformatori su uspešno dekontaminirani, hemijskom razgradnjom PCB-a a ujedno je ostvarena i hemijska regeneracija i poboljšanje izolacionih karakteristika ulja. Primenjena tehnologija ispunjava kriterijume dobre ekološke prakse (eng. BEP = best environmental practice). To znaĉi da je nakon dekontaminacije PCB u ulju prisutan u tragovima, ispod dozvoljenih vrednosti do 0.005%, a nus-produkti, tj. otpad ne sadrţi PCB. Ovaj proces je ispunjava i kriterijume najbolje raspoloţive tehnologije (eng. BAT = best available technology) jer uvaţava potrebe i zahteve elektroenergetskog sistema. Moguća je dekontaminacija PCB kontaminiranih transformatora razliĉitih snaga, konstrukcija, veliĉina i koliĉina ulja, sa razliĉitim koncentracijama PCB u ulju (od 50 do 6000 ppm), kao i sa znaĉajnim razlikama u stanju PCB kontaminiranog ulja.

Kljuĉne reĉi: polihlorovani bifenili, dekontaminacija ureĊaja, transformatori

UVOD

Zakoni u oblasti zaštite ţivotne sredine usklaĊeni sa Evropskim i prema Štokholmskoj konvenciji vlasnike elektriĉne opreme obavezuju da oznaĉe i deklarišu opremu prema sadrţaju PCB-a. Prema Štokholmskoj konvenciji oprema kontaminirana u opsegu 50 do 500 mg/kg moţe se upotrebljavati do kraja radnog veka ako je adekvatno identifikovana i obeleţena, ako je ispravna i ne curi, a poţeljno je da se trajno zbrine ili dekontaminira do 2025 godine [1].

Problem u ekspoloataciji PCB kontaminiranih transformatora postaje posebno ozbiljan ukoliko je transformator neispravan, ima loše karakteristike izolacionog sistema i curi, jer se tada povećava rizik od zagaĊenja okoline (zemljišta, vode, ţivog sveta), havarije transformatora i ekološkog akcidenta. Znaĉajan broj transformatora u elektroenergetskom sistemu Srbije karakterišu neki od navedenih problema. Ĉesto su izraţeni problemi pregrevanja izolacije (termiĉki kvarovi u bakarnim namotajima, na kontaktima regulatora napona, u magnetnom kolu...), gubitka izolacionih svojstava papirno-uljnog dielektrika usled povišene ovlaţenosti ili prisustva elektro-provodnih kontaminanta koji nastaju degradacijom sumpornih jedinjenja u izolacionom ulju, te je za neke transformatore primena postupka dekontaminacije hitna, u cilju smanjenja rizika eksploatacije.

Zbog potencijalne opasnosti koju mogu predstavljati po zdravlje ljudi i ţivotnu sredinu, Štokholmskom konvencijom je ukinuta i zabranjena proizvodnja i primena polihlorovanih bifenila, uprkos njihovim izuzetnim osobinama za primenu kao izolacionih fluida. Nakon uvoĊenja ovih restrikcijan zapoĉeo je razvoj tehnoloških procesa ĉiji je cilj uklanjanje i finalno odlaganje PCB-a, kako u primeni tako i u aspektu kontaminirane ţivotne sredine. Dominantna primena PCB-a je bila u izolacionim teĉnostima prvenstveno izolacionim uljima u elektriĉnoj opremi. Iako je sama proizvodnja PCB izolacionih ulja prestala pre više od tri decenije ureĊaji koji sadrţe PCB ulja ili mineralna ulja kontaminirana PCB-om su i dalje u primeni. Zbog višedecenijske primene, kao i redovnih remontnih zahvata na ureĊajima, procenjuje se da je danas volumen PCB kontaminiranih mineralnih ulja znatno veći od volumena PCB ulja.

U ovom radu je prikazan tehnološki postupak za dekontaminaciju PCB kontaminiranih ureĊaja i mineralnih izolacionih ulja.

A. Orlović i sar.: TEHNOLOGIJA DEKONTAMINACIJE IZOLACIONIH ULJA KONTAMINIRANIH...

18

MATERIJALI I METODE RADA

Procenjuje se da je danas na globalnom nivou operativno oko 40 postrojenja za dekontaminaciju PCB kontaminiranih ureĊaja i ulja. Iako ne postoji precizna definicija, tipiĉno se pod kontaminiranim ureĊajima podrazumevaju ureĊaji koji sadrţe ulje sa koncentracijom do 6000 mg/kg PCB-a. Ulja sa sadrţajem PCB-a višim od navedenog se obiĉno smatraju PCB uljima.

S obzirom na ĉinjenicu da se kontaminirani ureĊaji nalaze najćešće distribuirani u okviru celokupnog elektro-energetskog sistema, što podrazumeva široku geografsku rasprostranjenost, kao i zbog ĉinjenice da se sami ureĊaji mogu znaĉajno razlikovati po veliĉini, naponskom nivou i pogonskom stanju, prvenstveno se kao odluka o optimalnoj tehnologiji nameću dve opcije, stacionarno postrojenje i mobilno postrojenje.

Sledeći nivo odluke predstavlja izbor tehnološkog postupka koji je determinisan postojećim i dokazanim tehnologijama kao i BEP (BEP – best environmental practice) i BAT (BAT-best available technology) dokumentima [2]. U kontekstu hemijske tehnologije procesi koji se danas navode i primenjuju zasnovani su na sledećim kljuĉnim tehnološkim fazama i postupcima:

- Tehnologije zasnovane na ekstraktivnim metodama i destruktivnoj oksidacji, - Tehnologije zasnovane na adsorpionim metodama i

- Tehnologije zasnovane na razgradnji PCB-a hemijskim reakcijama.

TakoĊe, proces dekontaminacije PCB kontaminiranog ureĊaja u osnovi mora da bude tehnološki projektovan tako da se u limitiranom vremenu transformator nakon dekontaminacije moţe vrati u pogon. To podrazumeva da primenjena tehnologija treba da zadovolji sledeće zahteve:

Dekontaminaciju transformatora na licu mesta u periodu kada je moguće iskljuĉenje u limitiranom vremenskom periodu, što zahteva postrojenje odgovarajućeg kapaciteta postrojenja za dekontaminaciju.

Postizanje visokog stepena konverzije PCB-a radi efikasne dekontaminacije uzimajući u obzir moguć efekat „povratnog curenja PCB-a‖ i porast koncentracije PCB-a u ulju tokom dalje eksploatacije transformatora, što se ispituje minimum nakon tri meseca rada ureĊaja.

Dubinsko preĉišćavanje dekontaminiranog ulja i povratak izolacionih svojstava ulja, što zahteva postojanje terenske laboratorije za optimizaciju procesa i kontrolu kvaliteta PCB dekontaminiranog ulja.

Imajući u vidu sve zahteve koji se nameću izbor optimalnog procesa za dekontaminaciju PCB kontaminiranih ureĊaja poţeljno je da pozitivno odgovori na sledeće zahteve:

- Proces je takav da predstavlja minimalno mogući rizik po bezbednost i ţivotnu sredinu, - Proces je takav da ne zahteva, ili dominantno ne zahteva, dislokaciju PCB kontaminiranih materijala i ureĊaja,

- Proces treba da omogući ponovno iskorišćenje izolacionog ulja i materijala transformatora i - Proces treba da bude takav da omogući dekontaminaciju uz minimalne troškove.

Gore navedene zahteve moţe da ispuni tehnologija mobilnog postrojenja koja se locira na lokacijama na kojima se već nalaze kontaminirani ureĊaji, osim u sluĉaju ureĊaja koji su malih dimenzija i nalaze se u zaštićenim zonama, zonama stanovanja i sliĉno. Osim toga, uslovi recikliranja materijala i minimiziranja troškova praktiĉno iskljuĉuju primenu metode oksidativne destrukcije (sagorevanja) jer u tom sluĉaju se osim PCB-a uništava i mineralno ulje koje ĉini izrazito dominantan deo sadrţaja kontaminiranog ulja. Veliki znaĉaj pri izboru optimalnog rešenja za dekontaminaciju ureĊaja imaju hemijske i procesne karakteristike postrojenja, što u praktiĉnom smislu znaĉi da je poţeljno izbegavati procese povećanog rizika tj. one koji koriste opasne hemikalije, visoke pritiske i temperature i sliĉno [3-6].

Svi navedeni aspekti tehnološkog procesa koji se moţe primeniti pri dekontaminaciji PCB kontaminiranih ureĊaja se obraĊuju u Studiji uticaja na ţivotnu sredinu.

Hemijska koncepcija procesa za dekontaminaciju PCB kontaminiranih ureĊaja i mineralnih ulja reakcijom dehlorinacije, razvijena je u Institutu Nikola Tesla i proces je zaštićen patentom u Republici Srbiji (patent broj P-2012-0288, Glasnik Intelektualne Svojine, GIS 2015-1, strana 64-65). Tehnološka koncepcija procesa i projektovanje procesa uraĊeni su u saradnji Instituta Nikola Tesla i Tehnološko-metalurškog fakulteta Univerziteta u Beogradu. Mobilno postrojenje je

izvedeno u verziji šarţnog postupka kapaciteta do 2000 kg obraĊenog ulja dnevno.

Osnovu procesa ĉini reakcija dehlorinacije tj. razgradnje molekula PCB-a koja se odvija po mehanizmu nukleofilne aromatske substitucije korišćenjem alkalnih alkoksida kao reagujuće vrste za izvoĊenje reakcije. Organski deo molekula, derivati bifenila, zaostaju ili delimiĉno zaostaju u ulju, dok se hlor u vidu neogranske soli izdvaja iz ulja u separatnoj fazi ragensa. Ova tehnologija je primenjena u više izvedenih procesa i u relevantnim dokumentima se navodi kao tehnologija koja je u skladu sa principima najbolje ekološke prakse, eng. „BEP – best environmental practice‖.

Zbog mogućeg širokog spektra primene i ĉinjenice da se sa visokom efikasnošću mogu obraditi ulja i sa visokim sadrţajem PCB-a, transformatorska ulja sa i bez aditiva, nekorišćena ulja i ulja degradirana nakon duţe eksploatacije, razvijena tehnologija takoĊe ima sve elemente najbolje raspoloţive tehnologije, eng. „BAT-best available technology‖.


19

Tehnološki postupak dekontaminacije ulja razgradnjom PCB-a

Sekcija 1 Sekcija 2 Sekcija 3

Slika 1. Shema postupka PCB dekontaminacije Figure 1. Process flow diagram of PCB decontamination technology

Sekcija 1: Hemijska razgradnja PCB-a

U sekciji 1: dehlorinacija ulja, vrši se hemijska razgradnja molekula polihlorovanih bifenila na povišenoj temperaturi reagensom koji sadrţi jaku alkalni hidroksid i jedinjenje pogodno za formiranje reaktivnog alkoksida. Osnovna reakcija je nukleofilna aromatska supstitucija. Vreme kontakta reagens smeše zavisi od poĉetne koncentracije PCB-a i udela pojedinih PCB kongenera u smeši PCB derivata i sadrţaja inhibitora oksidacije u ulju (di terc. butil para-krezol, DBPC), i moţe da varira od 30 do 90 minuta. Kontinualnim monitoringom sadrţaja PCB-a tokom procesa dehlorinacije optimizuje se koliĉina reagens smeše, vreme kontakta i kontroliše se sadrţaj PCB u izlaznoj šarţi.

Nakon postupka dehlorinacije, tj. hemijske razgradnje PCB-a, tretirano mineralno ulje u sebi sadrţi odreĊenu koliĉinu zaostalog reagensa koji se mora ukloniti. Otpad koji nastaje nakon dehlorinacije predstavlja istrošen reagens koji ne sadrţi PCB, što je verifikovano merenjem sadrţaja PCB-a u istrošenom reagensu.

Sekcije 2 i 3: Preĉišćavanje dekontaminiranog ulja

Uklanjanje zaostalog reagensa iz ulja i povratak izolacionih osobina ulju nakon dehlorinacije izvodi se u sekcijama 2 i 3:

• sekcija 2: preĉišćavanje dekontaminirang ulja na kolonama punjenim specifiĉnim, aktiviranim adsorbentima (alumosilikatima) perkolacioni postupkom • sekcija 3: završna obrada, sušenje, degazacija i filtriranje ulja

Nakon uklanjanja zaostalog reagensa, sušenja i filtriranja, ulju se dodaje inhbitor oksidacije (di terc. butil para-krezol) u koliĉini od 0.3 do 0.35%.

Otpad koji nastaje tokom perkolacionog postupka je zauljeni adsorbent, koji ne sadrţi PCB. Ukupna koliĉina generisanog otpada se kreće od 4-6% raĉunato na koliĉinu obraĊenog ulja. Mobilno postrojenje je prikazano na Slici 2.

Slika 2. Mobilno postrojenje za dekontaminaciju PCB kontaminiranih ureĊaja Figure 2. Mobile unit for PCB decontamination of electrical equipment

Otpad 1

(istrošen reagens)

Otpad 2

(zauljeni adsorbent)

Sušenje i

filtriranje ulja

Ulje bez

PCB-a

UUlljjee ssaa

PPCCBB--oomm

PPrriipprreemmaa

uulljjaa

DDeehhlloorriinnaacciijjaa

uulljjaa

Perkolacija

(preĉišćavanje)

adsorbentima)


20

KONTROLA PROCESA PCB DEKONTAMINACIJE

Tokom procesa PCB dekontaminacije neophodno je pratiti sadrţaj PCB-a u cilju odreĊivanja optimalnog vremena reakcije i kontrole efikasnosti procesa i kvaliteta ulja nakon obrade. Izolacione osobine ulja i to: probojni napon ulja, sadrţaj vode u ulju i broj i veliĉina ĉestica u ulju nakon PCB dekontaminacije, moraju biti zadovoljavajuće, zbog ponovnog korišćenja dekontaminiranog ulja u transformatorima i vraćanja ureĊaja u rad.

Terenska laboratorija Instituta Nikola Tesla poseduje instrumente za merenje:

• sadrţaja PCB u ulju semikvantitativnom metodom (detekcija hlora), Dexil L2000 DX Chloride Analyzer, akreditovana metoda US EPA SW-846 metoda 9079 • probojnog napona ulja, Baur Oil Tester DPA 75C, akreditovana metoda IEC 60156 • sadrţaja ĉestica u ulju, HIAC PODS, akreditivana metoda IEC 60970 • sadrţaja vode u ulju, preko relativnog stepena zasićenja vode u ulju (RS, %), kapacitivnim senzorom (Domino)

Za preciznu kvantifikaciju PCB-a, izvode se merenja sadrţaja PCB metodom gasne hromatografije sa detektorom zahvata elektrona GC-ECD (eng. „electron capture detector‖). Odlukom Evropske komisije (Commision Decision 2001/68/EC), Evropski standard IEC 61619 se primenjuje kao referentna metoda za utvrĊivanje sadrţaja PCB u izolacionim teĉnostima [7]. Princip analize sadrţaja PCB je zasnovan na razdvajanju i identifikaciji pojednaĉnih PCB kongenera i njihovim sumiranjem u ukupni sadrţaj PCB u uzorku ulja. Analize se vrše na temperaturno programiranoj koloni, sa helijumom kao nosećim gasom. Visoka rezolucija gasnog hromatografa i velika osetljivost detektora na halogene elemente (brom, hlor) pruţaju mogućnost ne samo identifikacije Arohlora (najĉešće komercijalne smeše PCB) ili smeše Arohlorova (A) prisutnih u uzorku, već i kvantifikacije pojedinaĉnih kongenera PCB, obezbeĊujući niske limite detekcije (< 2 ppm) [8]. Metoda je primenljiva za nekorišćena, regenerisana ulja i za korišćene PCB kontaminirane izolacione teĉnosti.

REZULTATI I DISKUSIJA

U toku 2015. godine izvedena je dekontaminacija 97 energetskih transformatora u JP EPS PD Elektrovojvodina naponskog nivoa 20/10-0.4 kV na sledećim lokacijama: Ogranak Novi Sad, Ogranak Subotica, Ogranak Sombor, Ogranak Ruma, Ogranak Panĉevo i Pogon Vršac.

Opis postupka dekontaminacije

Nakon pripremnih aktivnosti: postavke zaštitnih folija, postrojenja, obezbeĊenja napajanja od 100-120 kW i postavke terenske laboratorije pristupalo se istakanju ulja iz transformatora u rezervoare. Dehlorinacija ulja je tipiĉno izvedena

sa vremenom kontakta od 30 do 60 minuta, a odvajanje reagensa od ulja u taloţniku i preĉišćavanje ulja na kolonama sa adsorbentima, protokom od oko 2400 l/h, ukupno tokom 3h. Finalna obrada ulja sušenjem i filtriranjem izvedena je mašinom za sušenje i filtriranje, protokom 3000 lit./h. Ukupno je dekontaminirano 33615 kg ulja, što odgovara masi opreme od oko 160 tona.

Rezultati PCB dekontaminacije

U okviru praćenja efikasnosti primenjenog procesa dekontaminacije ulja kao i kontrole kvaliteta obraĊenog ulja, u laboratoriji Instituta, nakon procesa izvedeno je ispitivanje sledećih karakteristika ulja na obraĊenim šarţama (tabela 1):

• Dielektriĉne ĉvrstoće ulja, • Neutralizacionog broja, • Faktora dielektriĉnih gubitaka i elektriĉne otpornosti ulja i • Kvalitativno ispitivanje sadrţaja PCB, na DEXIL L2000 DX Analyzer.

Tabela 1. Rezultati ispitivanja sadrţaja PCB i karakteristika ulja nakon procesa dekontaminacije Table 1. PCB content and insulating oil properties upon decontamination process

Lokacija Broj

šarţe PCB, ppm Up', kV/cm

Nb,

mgKOH/gu

tgδ,

‰ na 90°C

Ogranak Novi Sad 2 8 276 <0,01 2,9

3 8 260 <0,01 1,5

Ogranak Subotica 12 5 292 <0,01 0,8

13 5 276 <0,01 0,9

Ogranak Sombor 3 7 292 <0,01 2,1

4 10 288 <0,01 1,7

Ogranak Ruma 1 11 268 <0,01 1,7

2+3 10 288 <0,01 1,1

Ogranak Panĉevo i Pogon Vršac

1+2 3 280 <0,01 1,9

3+4 8 296 <0,01 2,7


21

Na osnovu rezultata prikazanih u tabeli 1, uoĉava se da su obraĊena ulja iz svih šarţi imala nizak sadrţaj kiselina i

faktor dielektriĉnih gubitaka, što ukazuje na visok stepen rafinacije ulja, kao i da su sve šarţe uspešno dekontaminirane (sadrţaj PCB u ulju je znaĉajno ispod 50 ppm). Nakon dobijenih zadovoljavajućih rezultata ulje je ponovo korišćeno u transformatorima.

Na slici 3. prikazani su rezultati dekontaminacije 96 PCB kontaminiranih transformatora u PD Elektrovojvodina. Ulja su dekontaminirana do niskih koncentracija PCB, u proseku od 2 do 5ppm, a nakon nalivanja u transformatore u proseku do 20 ppm, zbog mešanja dekontaminiranog ulja sa manjom koliĉinom PCB kontaminiranog ulja koja je zaostala u sudu transformatora (efekat povratnog curenja).

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60 70 80 90 100

Broj transformatora

Ko

nc

en

tra

cija

PC

B, p

pm

Koncentracija PCB

pre

dekontaminacije

Koncentracija PCB

nakon

dekontaminacije

Slika 3. Sadrţaj PCB u 96 transformatora 20/0.4 kV pre i nakon dekontaminacije u PD Elektrovojvodina Figure 3. PCB contents in 96 transformers of 20/0.4 kV voltage level before and after decontamination within PD

Elektrovojvodina

Ispitivanje sadrţaja PCB pre i nakon dekontaminacije izvedeno je kvanitativnom metodom na GC-ECD-u, prema metodi IEC 61619. U tabeli 2. prikazani su rezultati za 10 izabranih transformatora pre i nakon dekontaminacije.

Tabela 2. Rezultati merenja PCB-a u ulju transformatora 20/10-0.4 kV pre i nakon procesa PCB dekontaminacije Table 2. Results of PCB content determination using GC-ECD i transformer oils 20/10-0.4 kV before and after PCB

decontamination

Red.br. Transf.

PCB ppm, pre procesa dekontaminacije

PCB ppm, nakon procesa dekontaminacije, GC-ECD

1 866 13,1

2 260 12,4

3 846 17,3

4 680 6,4

5 103 16,1

6 61 17,1

7 492 11,6

8 527 20,0

9 276 22,0

10 697 14,0

Analizom uporednih rezultata merenja sadrţaja PCB, pre i nakon primenjenog procesa, prikazanih u tabeli 2, uoĉava se visoka efikasnost procesa u uklanjanju PCB, u širokom opsegu poĉetnih koncentracija. Na slici 5. prikazan je izgled hromatograma PCB molekula pre i nakon procesa dekontaminacije.


22

Slika 4. GC-ECD hromatogrami ulja pre dekontaminacije sa sadrţajem PCB-a od 269 ppm (gonji) i ulja nakon dekontaminacije sa sadrţajem PCB-a od 15 ppm (donji)

Figure 4. GC-ECD chromatogram of oil before decontamination with PCB content of 269 ppm (upper) and of oil after decontamination with PCB content of 15 ppm (lower)

Nakon izvedene dekontaminacije transformatori su vraćeni u eksploataciju. Verifkacija primenjenog postupka i

definisanje statusa transformatora po pitanju kontaminacije PCB-om odreĊuje se najmanje tri meseca nakon dekontaminacije, merenjem sadrţaja PCB u ulju, što je propisano standardom EN 5050 [5]. U tabeli 3. prikazani su rezultati sadrţaja PCB u ulju 22 transformatora, napona 20/10-0.4 kV nakon tri meseca pogona u ED Novi Sad. Svi transformatori su uspešno dekontaminirani, tj. svi sadrţe PCB ispod graniĉne vrednosti od 50 ppm.


23

Tabela 3. Rezultati PCB dekontaminacije 22 energetska transformatora 20/10-0.4 kV u ED Novi Sad na GC-ECD-u Table 3. Results of PCB decontamination of 22 power transformers 20/10-0.4 kV within ED Novi Sad as determined bz

GC-ECD

ZAKLJUĈCI

Dekontaminacija PCB kontaminiranih transformatora uspešno je izvedena primenom procesa dehlorinacije ulja u mobilnom postrojenju. U JP EPS, PD Elektrovojvodina dekontaminirano je 97 energetskih transformatora naponskog nivoa 20/10-0.4 kV, tj. 33615 kg ulja u opsegu koncentracija od 1067 do 50 ppm. Tri meseca nakon dekontaminacije izmereni sadrţaji PCB-a u ulju 22 transformatora iz Ogranka Novi Sad bili su ispod graniĉne vrednosti od 50 ppm. Otpad koji nastaje nakon procesa ne sadrţi PCB i generiše se u proseĉnoj koliĉini od oko 5%. Proces dekontaminacije PCB kontaminiranih ureĊaja i ulja, razvijen u Elektrotehniĉkom institutu Nikola Tesla i projektovan na Tehnološko-metalurškom fakluletu, potvrĊen je kao efikasno i ekonomiĉno rešenje za dekontaminaciji PCB kontaminiranih transformatora. Primenjeno rešenje sadrţi sve elemente najbolje raspoloţive tehnologije i najbolje ekološke prakse.

LITERATURA

1. „Priruĉnik za identifikaciju, voĊenje evidencije i sigurno rukovanje PCB opremom/ureĊajima i otpadom‖, Ministarstvo ţivotne sredine i prostornog planiranja Republike Srbije, februar 2010.

2. „Destruction and Decontamination Technologies for PCBs and other POPs wastes under the Basel Convention – Volume A‖, „Secreteriat of the Basel Convention‖, „International Environment House‖, 15 chemin des Anémones, CH-1219 Châtelaine, Switzerland.

3. S. Teslić, B. Bošković, V. Radin, J. Janković, „Mineralna transformatorska ulja kontaminirana piralenom (PCB-om) ―, EKO-JUSTUS II, Palić, 2010.

4. S. Teslić, J. Janković, B. Bošković, V. Radin, J. Lukić, S. Milosavljević, „Mineralna transformatorska ulja kontaminirana piralenom (PCB) - od identifikacije do rešavanja problema‖, VII Savetovanje o elektrodistributivnim mreţama Srbije i Crne Gore, R-1.11, Vrnjaĉka Banja, 2010.

5. J. Lukić, D. Nikolić, V. Mandić, S. Milosavljević, A. Orlović, „Dekontaminacija PCB kontaminiranih transformatora‖, P A2 01, 30.savetovanje CIGRE Srbija, Zlatibor, 29.05.-03.06.2011.

6. CENELEC Technical Report, final draft: ―Guidelines for inventory control, management, decontamination, and or disposal of electrical equipment and insualting liquids containing PCBs‖, CLC/Fpr TR 50503:2009 E

Lokacija Red.br. trans.

PCB ppm, pre procesa

dekontaminacije

PCB ppm, tri meseca nakon procesa

dekontaminacije

ED Novi Sad

1 866 21

2 697 19

3 527 26

4 260 19

5 78 6

6 276 34

7 189 19

8 166 13

9 140 11

10 139 26

11 138 16

12 82 14

13 64 4

14 112 7

15 95 20

16 89 10

17 89 10

18 83 12

19 72 7

20 100 14

21 883 38

22 468 15


24

7. IEC 61619/1997: ―Insulating liquids – Contamination by polychlorinated biphenyls (PCBs) – Method of determination by capillary column gas chromatography‖.

8. BS EN 50503. „Fluids for electrotechnical applications. Standard for the inventory control, management, decontamination and/or disposal of electrical equipment and insulating liquids containing PCBs‖.

TECHNOLOGY FOR DECONTAMINATION OF INSULATING OILS CONTAMINATED BY POLYCHLORINATED BIPHENYLS

Aleksandar Orlović1, Sandra Glišić1, Jelena Lukić2

1Faculty of technology and metallurgy, Karnegijeva 4, 11000 Belgrade Serbia,[email protected], [email protected]

2Electrotechnical institute Nikola Tesla, Koste Glavinića 8a, 11000 Belgrade Serbia, [email protected]

Environmental laws and regulations require owners of the equipment contaminated by polychlorinated biphenyls to perform screening and labelling of PCB contaminated units. Operation of PCB contaminated equipment is associated with risks which might lead to emissions into the environment, accidents due to malfunctioning of transformers, possible spills into the environment, ignition of oils and their incomplete oxidation leading to formation of highly toxic and damaging substances with serious consequences. One of the possible and efficient ways of mitigation of such risks is decontamination of PCB contaminated equipment, particularly in the case of equipment which is required to continue operation. This paper presents results of the application of the process for PCB contaminated equipment decontamination by chemical dechlorination. Decontamination has been performed within energy companies in Serbia, JP EMS and JP EPS. Transformers were successfully decontaminated by chemical decomposition of PCBs followed by the improvement of all other application characteristics of insulating oils. The applied technology fulfils the criteria set out as BEP (Best Environmental Practice). This is the consequence of the fact that following decontamination procedure PCBs are present in oils only in minute concentrations of up to 0.005%, wt. and by-products do not contain PCBs. The process also meets the criteria of BAT (Best Available Technology) as it is fully in compliance with the requirements of the electrical grid and the energy supply system. It is possible to perform decontamination of transformers of different scales, with respect to power, size and construction, as well as of oils of varying general conditions containing different levels of PCB concentrations (from 50 to 2000 ppm).

Key words: polychlorinated biphenyls, equipment decontamination, transformers


25

ODREĐIVANJE SADRŢAJA GASA U UPAKOVANIM NAMIRNICAMA BEZ OŠTEĆENJA AMBALAŢE

Dragiša Savić1, Bojana Danilović1, Luca Poletto2, Lorenzo Cocola2, Massimo Fedel2

1Tehnološki fakultet u Leskovcu, Univerzitet u Nišu, Bulevar Oslobodjenja 124, 16000 Leskovac, Srbija. [email protected]

2CNR Institut za fotoniku i nanotehnologije, Padova, via Trasea 7, 35131 Padova, Italija, [email protected]

ISSN 2232-755X UDC: 664.854:634.1/.7

DOI: 10.7251GHTE16VI025S

U radu su opisani principi i primeri industrijske primene tehnike merenja sadrţaja gasa (O2, H2O, CO2) unutar upakovanih namirnica bez direktnog kontakta i oštećenja pakovanja (boce, ĉaše…) u realnom vremenu. Tehnika je zasnovana na Tunable Diode Laser Apsorption Spectroscopy (TDLAS), a prednosti su: selektivnost, bez kontakta i oštećenja pakovanja, kao i bez uticaja pritiska, temperature ili brzine kretanja uzorka. Metod se praktiĉno primenjuje za odreĊivanje sadrţaja O2 i CO2 u industriji penušavih vina, sokova, kao i za praćenje curenja kod vakum upakovanih voćnih sokova i analize gasa kod namirnica upakovanih u modifikovanu atmosferu (voće i sirevi). Pored toga, tehnika omogućava odreĊivanje nivoa kvarenja upakovanih namirnica jer većina mikroorganizama kvarenja oslobaĊa CO2 u toku svog rasta. Zbog toga, CO2 moţe biti dobar indikator za otkrivanje kontaminacije u ranim fazama, dok je sadrţaj O2 pokazatelj kvaliteta namirnice i procesa zaptivanja pakovanja.

Kljuĉne rijeĉi: TDLAS, sadrţaj gasa, pakovanje namirnica

UVOD

Stalnim usavršavanjem procesa, in-line analiza gasova u realnom vremenu postaje kljuĉni problem u automatizaciji razliĉitih industrijskih procesa. Poseban izazov predstavlja analiza sastava i ćistoće procesnih gasova, dijagnostika u medicini i praćenje poljoprivredne i industrijske emisije gasova. Sve stroţi zahtevi i regulative u zaštiti ţivotne sredine vode razvoju metoda i tehnika za merenje koncentracije razliĉitih gasova primenom preciznih metoda [1]. Primena lasera za lasersku spetroskopiju stalno raste poslednjih godina, pri ĉemu je konstruisan veliki broj aparata za odreĊivanje sadrţaja gasova u industriji, ali u istraţivaĉke svrhe.

Od kada je prvi put predstavljena 1970. godine, tehnika zahnovana na Tunable Diode Laser Apsorption Spectroscopy (TDLAS) široko se koristi za odreĊivanje malih koncentracija gasova u industrijskim procesima, medicini i biomedicinskim istraţivanjima, praćenju zagaĊenja atmosfere itd. [2]. Osetljivost TDLAS tehnike je daleko veća u odnosu na konvencionalne hemijske senzore, tako da omogućava odreĊivanje sadrţaja gasova u veoma malim koncentracijama (ppmv ili ĉak ppbv), na primer u gasovima izdisaja.

U nekim granama industrije, posebno farmaceutskoj i prehrambenoj, potrebno je odreĊivati sadrţaj gasa u upakovanim proizvodima. Postoji nekoliko tehnika odreĊivanja sadrţaja gasa u upakovanim proizvodima, od kojih

većina zahteva izdvajanje uzoraka sa proizvodne linije i oštećenje ambalaţe kako bi se obavilo merenje, kao i prenošenje uzorka do instrumenta za merenje. MeĊutim, primena spektroskopskih tehnika moţe olakšati i ubrzati postupke odreĊivanja sadrţaja gasa u upakovanim proizvodima, pri ĉemu se ne oštećuje ambalaţa, a merenja odvijaju direktno na proizvodnoj liniji bez zaustavljanja procesa pakovanja.

U ovom radu su prikazani osnovni principi TDLAS tehnike, primeri praktiĉne primene u industriji, kao i mogućnosti primene u prehrambenoj industriji za praćenje sadrţaja gasova u upakovanim namirnicama, kao i odreĊivanje kontaminacije.

OSNOVE LASERSKIH TEHNIKA ODREĐIVANJA SADRŢAJA GASA

U tehnikama optiĉke apsorpcione spektroskopije moţe se koristiti podesivi polukonduktivni laser (tunable semiconductor laser) kao izvor svetlosti, pa se tehnike nazivaju TDLAS (tunable diode laser spectroscopy). TDLAS je visokoselektivna tehnika za odreĊivanje atmosferskih sastojaka u tragovima (osetljivost ppb). Zasniva se na ĉinjenici da svaki molekul ima jedinstvene apsorpcione karakteristike ili ‗‘otisak prsta‘‘. TDLAS obuhvata merenje prigušenja (atenuacije) usled apsorpcije laserskog zraka na odreĊenoj talasnoj duţini dok prolazi kroz region merenja. Na

talasnim duţinama izvan podešenih nema apsorpcije svetlosti od strane gasa koji se analizira, pri ĉemu se talasna duţina svetlosti podešava za skeniranje jedne ili više apsorpcionih linija gasa. Mera prigušenja moţe dati podatke o koncentraciji, pritisku, temperaturi i brzini analiziranog gasa [3].

Osnovni TDLAS ureĊaj se sastoji od podesivog diodnog lasera (emituje monohromatsku svetlost na apsorpcionoj liniji gasa), transmisione optike (usmerava laserski zrak), apsorpcionog medijuma (uzorak gasa u ćeliji propusnoj za laserski

D. Savić i sar.: ODREĐIVANJE SADRŢAJA GASA U UPAKOVANIM NAMIRNICAMA BEZ OŠTEĆENJA AMBALAŢE

26

zrak), optike risivera i detektora (meri transmisiju) (slika 1). Svetlost iz lasera prolazi kroz uzorak gasa i usmerava se na detektor. Talasna duţina lasera se podešava malom skalom (obiĉno 0,5 nm) variranjem ulazne struje, i to za karakteristiĉne apsorpcione linije vrste gasa koji se odreĊuje na putu laserskog zraka. Molekul koji se odreĊuje absorbuje lasersku frekvenciju što umanjuje intezitet transmisije na toj frekvenciji koji beleţi fotodioda u funkciji talasne duţine (slika 1).

Mereni transmisioni trag moţe biti konvertovan u apsorpcioni spektar, a integrisana površina ispod apsorpcionog pika moţe biti direktno dovedena u korelaciju sa koncentracijom primenom Beer–Lambertovog zakona. Prema ovom zakonu, u sluĉaju slabe apsorpcije, intenzitet transmitovane svetlosti kroz uzorak duţine L i koncentracije N izraĉunava se [2]:

I(ν)= I0(ν)-LN I0(ν) σ(ν)

gde je I0(ν) poĉetni intenzitet svetlosti na talasnoj duţini ν, a σ(ν) je apsorpcioni koeficijent.

Merenjem relevatnih parametara (npr., integrisana apsorpciona površina, temperatura i pritisak gasa, kao i duţina putanje zraka), ovim zakonom se moţe izraĉunati koncentracija gasa uz primenu neznatne kalibracije ili dodatnih sredstava za merenje i analizu [4].

Talasna duţina se podešava tako da obuhvati najmanje jednu apsorpcionu liniju molekula ĉija se koncentracija odreĊuje preko fotodetektora, a signal se analizira da bi se dobila srednja koncentracija gasa u uzorku na putu laserskog zraka. Kako svaki molekul absorbuje svetlost razliĉite talasne duţine, potrebne su razliĉite laserske diode za merenje razliĉitih molekula, iako postoje tehnike sa multiplekser ureĊajem (WM-TDLAS) za istovremeno merenje više molekula jednim laserom [5].

Primena TDLAS tehnike u merenju sadarţaja gasova omogućuje [6]:

visoku osetljivost u merenju malih koncentracija gasa (ppm do ppb, ĉak i ppt), merenja na mestu odreĊivanja (in situ), bezkontaktna merenja, rad na sobnoj ili povišenoj temperaturi, odreĊivanje gasova koji uzrokuju taloţenje na ĉvrste površine i izradu lako pokretljivih instrumenata.

U poreĊenju sa drugim metodama, kao što je gasna hromatografija, TDLAS tehnika pokazuje visoku selektivnost, niţu

cenu i bezbedniji rad [6].

Slika 1. Šema standarnog TDLAS ureĊaja [4] Figure 1. Standard TDLAS set up [4]

INDUSTRIJSKA PRIMENA LASERSKE SPEKTROSKOPIJE

Gasovi ĉije se koncentracije mogu odrediti primenom TDLAS tehnike, talasne duţine laserskog zraka, kao i njihova dosadašnja primena prikazani su u tabeli 1. Primeri primene ove tehnike su vrlo raznovrsni sa zajedniĉkim karakteristikama da omogućuju odreĊivanje sadrţaja gasa u koncentracijama ppb direktno na mestu odreĊivanja (in situ) i u realnom vremenu.

U cilju optimizacije industrijskih procesa, pre svega u petrohemijskoj industriji i kontroli sagorevanja gasova u ureĊajima za sagorevanje i motorima sa unutrašnjim sagorevanjem, potrebno je praćenje sadrţaja nekoliko gasova. OdreĊuju se koncentracije C2H2, O2, CH4, CO, CO2, H2O, NOx u cilju povećanja efikasnosti sagorevanja, kontrole emisije gasova staklene bašte, unapreĊenja i produktivnosti procesa, kao i smanjivanja troškova procesa [7].


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Naftna industrija, posebno kontrola cevovoda prirodnog gasa, zahteva proveru sadrţaja: vodene pare (zaštita od korozije; gas se ne isporuĉuje ukoliko je ‗vlaţan‘), CO2 (zaštita od korozije jer CO2 reaguje sa H2S i H2O i izaziva koroziju ĉeliĉnih cevi), opasnih gasova (H2S je korozivni, otrovni i eksplozivni gas nusproizvod petrohemijske industrije, kao i gas uzroĉnik kiselih kiša), kao i kontrolu curenja u cevovodima (CH4 - gas staklene bašte) [7].

OdreĊivanje sadrţaja gasova u zaštiti ţivotne sredine obuhvata, uglavnom, kontrolu emisije gasova staklene bašte, tj. kvantifikacija emisije CO2 i CO (nastaju u procesima sagorevanja), C2H6 (vaţan gas staklene bašte, ukazuje na termogeno ili biološko poreklo CH4), CH4 (30 puta više doprinosi efektu staklene bašte od CO2), NH3 (dodaje se u procesima sagorevanja kako bi se smanjila emisija dimnih NOx i nastali bezopasni N2 i voda), SO2, NOx (nastaje za vreme sagorevanja, a pri reakciji sa SO2 uzrokuje nastanak kiselih kiša) [7, 8].

U oblasti bezbednosti, TDLAS se primenjuje za odreĊivanje gasova u cilju praćenja izloţenosti radnika toksiĉnim gasovima (kancerogeni C2HO) u toku procesa proizvodnje, curenja gasova i kvalitet prirodnog gasa u cevovodima (CH4, CO2), ranog otkrivanja poţara (CO u dimu), kontrole toksiĉnih gasova (HF produkt sagorevanja, SO2, H2S) i prevencije eksplozija (C2H2) [6].

OdreĊivanje sadrţaja pojedinih gasova u izdisaju je vrlo ĉesta primena TDLAS metoda u medicini. Prati se sadrţaj C2H6

i C2H2 (biomarkeri za astmu, šizofreniju ili rak pluća), CH4 (za utvrĊivanje intestinalnih poremećaja), CO (biomarker za astmu i respiratorne infekcije), CO2 i NH3 (biomarkeri za Helicobacter pylori infekcije), kao i NOx (biomarkeri za plućne bolesti i astmu). TakoĊe, u toku primene pojedinih hirurških instrumenata (lasera, bušilica i ultrasoniĉnih skalpela) dolazi do stvaranja hirurškog dima koji se sastoji od toksiĉnih i kancerogenih gasova ĉiju je koncentraciju potrebno pratiti (tabela 1) [6].

Tabela 1. Gasovi ĉije se koncentracije mogu odrediti primenom TDLAS tehnike, talasne duţine laserskog zraka, kao i njihova dosadašnja primena (preciznost odreĊivanja ppb) [modifikovano prema 6, 7]

Table 1. Gases determined by TDLAS technique, wavelength of apsorption lines, and up to date application (up to ppb precision) [modified according to 6, 7]

Gas/Gas Talasna duţina apsorpcije, nm/ Wavelength, nm

Primena/Application

Kiseonik, O2 760, 1269 Optimizacija procesa (kontrola sagorevanja, maksimiziranje snage)

Medicina (analiza gasa disanja)

Vodonik fluorid, HF 1278, 2475

Optimizacija procesa (hlaĊenje gasa, proizvodnja aluminijuma)

Bezbednost (kontrola emisije)

Medicina (hirurški gasovi)

Vodena para, H2O 935, 1392, 1854, 1877, 2652

Naftna industrija (vodena para u cevovodima),

Zaštita ţivotne sredine (praćenje promene klime),

Kontrola procesa (procesi sagorevanja)

Automobilska industrija (optimizacija rada motora)

Svemir (otkrivanje izotopa)

Istraţivanja (merenje odnosa izotopa)

Amonijak, NH3 1512, 3000 Optimizacija procesa (kontrola emisije)


Ugljen-monoksid, CO 1568, 2330, 4610

Optimizacija procesa (kontrola sagorevanja)

Zaštita ţivotne sredine (praćenje emisije),

Bezbednost (rano otkrivanje poţara),

Medicina (analiza gasa disanja, hirurških gasova)

Ugljen-dioksid, CO2 1581, 1590, 2004, 2051, 2682, 2770, 4225

Kontrola procesa (procesi sagorevanja, proizvodnja ĉelika, spaljivanje otpada),

Zaštita ţivotne sredine (praćenje emisije),

Bezbednost (kontrola kvaliteta u cevovodima prirodnog gasa),


Automobilska industrija (kontrola emisije),

Svemir (otkrivanje izotopa)

Istraţivanje (selektivno otkrivanje izotopa)

Hlorovodonik, HCl 1742, 3395 Bezbednost (kontrola emisije)

Vodonik-sulfid, H2S 1590, 2640 Optimizacija procesa (praćenje korozije)

Bezbednost (kontrola emisije)


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Metan, CH4 1654, 1689, 3270

Optimizacija procesa (kontrola sagorevanja)

Zaštita ţivotne sredine (otkrivanje gasova staklene bašte)


Acetilen, C2H2 1520, 3030

Optimizacija procesa (kontrola kvaliteta)


Bezbednost (prevencija eksplozija)

Formaldehid, C2HO 3560 Bezbednost (praćenje izloţenosti na radnim mestima)

Azot-oksidi, NOx 1814, 2270, 2670, 2860, 3420, 4470, 5255

Zaštita ţivotne sredine (kontrola emisije)

Medicina (analiza gasa disanja, praćenje medicinskog gasa)

Sumpor-dioksid, SO2 2460, 4020 Bezbednost (kontrola emisije)

Etan, C2H6 1640, 3360 Zaštita ţivotne sredine (kontrola emisije)


U automobilskoj industriji, TDLAS ureĊaji se primenjuju za odreĊivanje CO, CO2, NOx i H2O u izduvnim gasovima, a što predstavlja kontrolu emisije ovih gasova i smanjenje zagaĊenja vazduha.

U svemirskim istraţivanjima, TDLAS ureĊajima instaliranim u NASA letilicama odreĊuje se sadrţaj CO2 i H2O u uzorcima atmosfere i tla nebeskih tela koje posećuju ove letilice.

TDLAS ODREĐIVANJE GASOVA U PREHRAMBENOJ INDUSTRIJI

Sadrţaj gasa u prehrambenoj industriji potrebno je odreĊivati iz sledećih razloga:

provere zaptivenosti i propustljivosti ambalaţe, odnosno otkrivanje curenja gasa (kod liofiliziranih ili proizvoda

upakovanih u vakuumu), utvrĊivanja efikasnosti procesa sušenja (kod sušenih proizvoda, npr, povrća), analize atmosfere proizvoda upakovanih u modifikovanoj atmosferi (npr., meso, voće), merenje sadrţaja gasa i pritiska na proizvodnoj liniji (proizvodi upakovani pod pritiskom gasa), praćenje fermentacionog procesa (npr, CO2 i O2 koncentracija kod vina i piva) i praćenje i kontrola kontaminacije proizvoda (povećan sadrţaj CO2 ukazuje na prisustvo mikroorganizama).

TDLAS tehnika se moţe primeniti za odreĊivanje sadrţaja gasova u pakovanjima koja imaju minimalnu transparetnost za laserski zrak koji se moţe meriti detektorom (obiĉno je oko 5%), što znaĉi za sve vrste plastiĉne i staklene ambalaţe (boce, kutije, tegle, ĉaše, kese…), dok nije primenljiva za laser nepropusne materijale, kao što je aluminijum (limenke, vreće, folije…). Laserski zrak prolazi kroz prostor iznad proizvoda, a intenzitet se beleţi foto-risiverom i istovremeno meri sadarţaj gasova u pakovanju. Razvijeni su i primenjeni u industrijskom procesu ureĊaji za odreĊivanje sadrţaja gasa u [9]:

karboniziranim proizvodima (gazirani sokovi, pivo, penušava vina), prozvodima punjenim u atmosferi azota (negazirana voda, ĉaj, vina) i

pasterizovanim ili toplopunjenim proizvodima (voćni sokovi, marmelada, paradajz sos).

Sadrţaj O2 i CO2 se, najĉešće, odreĊuje u industriji flaširanih proizvoda. Sadrţaj i pritisak CO2 je potrebno pratiti u industriji penušavih vina, dok je sadrţaj O2 znaĉajan kod praćenja starenja vina. Oba gasa su od znaĉaja i u proizvodnji gaziranih sokova.

Primer za praktiĉnu primenu in situ merenja sadrţaja CO2 je ureĊaj (FT System, Italija) instaliran na liniju za proizvodnju penušavih vina (slika 2A) [9], a u cilju izdvajanja boca koje nemaju ţeljeni pritisak od 5 bar u prostoru iznad. UreĊaj beskonaktno meri pritisak u svim bocama bez uticaja boje ili materijala boca, kao i vrste zatvaraĉa, pri ĉemu je dovoljna propustljivost ambalaţe od 5% [9]. Isto tako, variranje u obliku boce usled fabriĉkih grešaka i koliĉina punjenja ne utiĉe na merenja. Brzina merenja jednog uzorka (boce) je 10 ms, zbog ĉega je moguće izvršiti merenja u 1200 boca/min. Isti proizvoĊaĉ opreme za kontrolu procesa zaptivenosti i kvaliteta upakovanih proizvoda razvio je TDLAS ureĊaj za odreĊivanje nivoa curenja u liniji za toplo punjenje sokova u boce od PET ambalaţe omotane folijom (slika 2B) uz brzinu merenja od 60 boca/min [9].


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A

B

Slika 2. In situ ureĊaji zasnovani na TDLAS tehnici za odreĊivanje sadrţaja CO2 u penušavim vinima (A) i H2O toplopunjenim sokovima (B) [9]

Figure 2. In situ instruments based on TDLAS technique for measuring CO2 in sparkling vine bottles (a) and hotfilled juice containers (B) [9]

Pored odreĊivanja sadrţaja gasova u bocama, merenje sadrţaja gasa moţe se vršiti u namirnicama upakovanim u modifikovanoj atmosferi (MAP) u cilju odreĊivanja propustljivosti pakovanja, ispravnosti procesa pakovanja (precizan odnos i sadrţaj gasa) i promena u toku skladištenja (starenja, fermentacije, zrenja...) proizvoda, kao što su hleb, voće ili meso. Razliĉiti pojedinaĉni TDLAS ureĊaji za odreĊivanje sadrţaja gasa izraĊeni su zavisno od vrste pakovanja za

odreĊivanja CO2 i O2. Instrumenti mogu raditi u transmisionom ili refleksionom (izvor laserskog zraka i detektor se nalaze sa iste strane, pa se snima odbijeni zrak, za pakovanja koja su transparetna samo na jednoj strani, npr, poklopac) modu. Takav ureĊaj za diskontinualno merenje sadrţaja O2 u namirnicama upakovanim u MAP nudi proizvoĊaĉ Gasporox, Švedska (slika 3A).

Laboratorija za optiĉka istraţivanja Instituta za fotoniku i nanotehnologije (Padova, Italija) uĉestvuje u konstruisanju i izradi instrumenata za odreĊivanje sadrţaja gasova u upakovanim proizvodima primenom TDLAS ureĊaja. U okviru nekoliko projekata, Laboratorija je sprovela istraţivanja i konstruisala ureĊaje za laboratorijsko odreĊivanje H2O, CO2 i O2, ali i za industrijsku primenu. U primeni su ureĊaji za kontrolu atmosfere u MAP upakovanim proizvodima (slika 3B). Isto tako, u industrijskoj primeni je in line ureĊaj za merenje sadrţaja O2 u cilju provere MAP atmosfere i propustljivosti kesa sa mozzarela sirom (slika 4) [12]. Automatizovan ureĊaj selektivno odvaja pakovanja sa lošom propustljivošću. Vrši se provera difuzivnosti materijala koje se pakuju u vrećice izgraĊene od mešavine polieilena i najlona, pri ĉemu sadrţaj kiseonika treba da bude ispod 5%.


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A B

Slika 3. UreĊaji za merenje sadrţaja gasova u namirnicama upakovanim u modifikovanoj atnosferi: (A) Gasporox, Švedska [10], (B) laboratorijski ureĊaj LUXOR, Italija [11]

Figure 3. Instruments for measuring gas content in MAP packed food: (A) Gasporox, Sweden [10], (B) laboratory device LUXOR, Italy [11]

Slika 4. UreĊaj za in-line merenje sadrţaja O2 u MAP upakovanom Mocarela siru u vrećama razliĉite veliĉine [12] Figure 4. In-line istrument for measurement of O2 content in plastic bags with Mozzarella cheese [12]

PRAĆENJE SADRŢAJA GASA KAO POKAZATELJA ISPRAVNOSTI I BEZBEDNOSTI HRANE

Sveţa ili pripremljena hrana ĉesto moţe biti kontaminirana razliĉitim patogenim ili mikroorganizmima kvarenja hrane. Zbog toga, odreĊivanje kritiĉnih kontrolnih taĉaka u toku pripreme hrane i sistema automatske kotrole je znaĉajno u cilju uklanjanja ili minimiziranja kontaminacije [13]. Kvarenje je primarno posledica rasta mikroorganizama koji preţivljavaju temperaturni tretman sirovine i proizvoda i/ili postprocesne kontaminacije [14].

Procenjuje se da se u svetu godišnje baca oko 1,3 milijarde tona hrane, što je oko trećina godišnje proizvodnje [15]. Hrana se baca zbog nedovoljne svesti potrošaĉa, neusklaĊenosti sa zahtevima kvaliteta i bezbednosti, prevremenog kvarenja, nekorišćenja pre roka upotrebe, navika potrošaĉa i nedostatka koordinacije izmeĊu uĉesnika u lancu

snabdevanja. MeĊutim, hrana koja se baca još uvek moţe biti korišćena, tako da se procenjuje da oko 40% baĉene hrane moţe biti jestivo. Da bi se utvrdila ispravnost i bezbednost hrane, potrebno je obaviti detaljne analize.

Analizira se mali deo hrane (oko 1%), pri ĉemu se testovi sprovode u specijalizovanim laboratorijama sa skupom opremom i obuĉenim osobljem. Zbog toga, nameću se zahtevi za analizom in situ i/ili in line uz korišćenje jeftinih, lako


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pokretnih ureĊaja kojima se lako rukuje, kao i direktna analiza u lancu snabdevanja i u toku celog veka trajanja proizvoda.

Stepen kvarenja u mnogim vrstama hrane vezan je za promenu koncentracije sadrţaja gasova, tako da njihov nivo moţe biti dobar indikator za prepoznavanje kontaminacije u ranoj fazi. Praćenje sadrţaja, na primer, CO2 moţe spreĉiti bacanje hrane na bazi oznake ―najbolje do‘‘, već na osnovu trenutnog stanja merenjem koncentracije koja je dovedena u korelaciju sa nivoom prisustva nepoţeljnih mikroorganizama. Isto tako, brzo odreĊivanje sadrţaja O2 u realnom vremenu moţe biti indikator kvaliteta proizvoda ili zaptivenosti pakovanja [16]. Manje O2 u pakovanju (npr, MAP) smanjuje mogućnost javljanja razgradnje hrane i rasta plesni. U suprotnom, povećana koncentracija O2 ukazuje na oštećenje pakovanja i curenje gasa. Na taj naĉin, brzo i jednostavno odreĊivanje sadrţaja O2 tehnikama TDLAS u upakovanim namirnicama moţe spreĉiti bacanje hrane koja nije ukvarena.

PRAĆENJE PROMENE SADRŢAJA CO2 U FERMENTISANIM MLEĈNIM NAPICIMA

TDLAS tehnika praćenja sadrţaja gasa moţe biti iskorišćena u laboratorijskim uslovima za praćenje promena u hrani ili upakovanim proizvodima u toku skladištenja. Iako je prouĉavan uticaj gasova, posebno CO2 na kvalitet i ispravnost mleĉnih proizvoda [17], ne postoji dostupna literatura praćenja i odreĊivanje veze izmeĊu sadrţaja gasova u fermentisanim mleĉnim proizvodima (FMP) i njihove bezbednosti i sigurnosti. Naime, sadrţaj gasova, pre svega CO2 moţe ukazivati na prisustvo nekih mikroorganizama kvarenja hrane ili izazivaĉa bolesti.

Rok trajanja FMP je ograniĉen na vreme u kome je proizvod bezbedan za konzumiranje i njegova senzorna svojstva ostaju prihvatljiva za potrošaĉa. Sveţi jogurt je najbolji u periodu prvih nekoliko nedelja roka trajanja, a nakon toga javlja se opadanje senzornih svojstava [14]. Period skladištenja koji osigurava nepromenjena senzorna svojstva u uslovima ĉuvanja na hladno za probiotski jogurt je oko 3 nedelje [18].

U cilju praćenja razvoja gasa u toku skladištenja, konstruisan je, kalibrisan i validiziran ureĊaj za merenja i kontinuirano praćenje sadrţaja CO2 u upakovanim FMP [19], jogurtu i kiselom mleku upakovanim u ĉašama i bocama razliĉitih zapremina (slika 5). Potrebno je kontinualno merenje sadrţaja CO2 u toku inkubacije, a u cilju utvrĊivanja veka trajanja proizvoda zavisno od naĉina skladištenja. UreĊaj je kalibrisan posebnim protokolom [20] koji omogućuje kalibraciju za sve vrste pakovanja fermentacionog proizvoda. Isto tako, sprovedeni su validacioni testovi na raliĉitim pakovanjima koji su pokazali taĉnost u rasponu 0.19-0.23%, kao i rezoluciju odreĊivanja 60-160 ppm na standarnoj

temperaturi i pritisku [19].

Slika 5 Izgled ureĊaja (A) [21] i kalibracija ureĊaja (B) [19] za kontinualno merenje sadrţaja CO2 u upakovanim fermentisanim mleĉnim proizvodima

Figure 5 The construction (A) [21] and the calibration (B) [19] of device constructed for non-destructive measurement of CO2 content in packages of fermented milk products

UreĊaj je korišćen za praćenje nastanka CO2 u toku skladištenja razliĉitih FMP zavisno od uslova skladištenja. Pokazano je da sadrţaj CO2 u toku ĉetiri dana skladištenja na 30oC (povišena temperatura termostatiranja u cilju ubrzanja procesa) linearno raste do koncentracije oko 7% u prostoru iznad punjenja u bocama od 500 ml jogurta, pri ĉemu se boce ne nadimaju [22]. Broj kvasaca koji bi uzrokovao povećani sadrţaj CO2 nije odreĊen u prvom danu praćenja, ali nakon 2 dana otkriveni su na nivou 1,7-2,9 logCFU/ml zavisno od vrste fermentisanog proizvoda, pri ĉemu zadrţavaju tu brojnost do kraja praćenja.


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U cilju odreĊivanja kritiĉne koncentracije CO2 koji bi ukazivao na kvarenje fermentisanog napitka, uzorci su kontaminirani sa kvascem Candida kefyr (izolovan iz ukvarenog jogurta) na poĉetnom nivou 1 i 5 CFU/ml [21]. Istraţivanja su pokazala da TDLAS odreĊivanje sadrţaja CO2 u upakovanim FMP moţe ukazati na nivo kvasaca kontaminanata. Sadrţaj CO2 iznad 6% moţe se smatrati kritiĉnim za mikrobiološko kvarenje jer ova koncentracija predstavlja taĉku ubrzanog rasta kvasaca [21]. Ovo ukazuje da metod TDLAS odreĊivanja sadrţaja CO2 u prostoru iznad punjenja u upakovanim FMP moţe uspešno sluţiti za odreĊivanje prisustva kvasaca, a što znaĉi ukazivati na neadekvatni proces proizvodnje, skladištenja i, kao krajnji cilj smanjiti ekonomske gubitke u toku proizvodnje.

ZAKLJUĈCI

Potreba za merenjem sadrţaja gasova u realnom vremenu, in line i sa velikom preciznošću, dovelo je do razvoja i primene spektroskopskih ureĊaja u naftnoj, automobilskoj i industriji zaštite ţivotne sredine, kao i medicini, svemirskim istraţivanjima i drugim oblastima. Tehnika primene laserske apsorpcione spektroskopije sa podesivim diodnim laserom (TDLAS) ima prednosti visoke osetljivosti (odreĊivanje u koncentracijama do ppb), jednostavne konstrukcije i mobilnosti ureĊaja i relativno malih investicija. Primenom ove tehnike u industriji odreĊuje se i meri sadrţaj CO2, CO, O2, H2O, CH4, C2H2 i drugih gasova u cilju praćenja emisije štetnih gasova, zaštite ljudi, optimizacije i praćenja procesa, dijagnostike bolesti i drugo.

Posebno je znaĉajno odreĊivanje gasova u prehrambenoj industriji u cilju provere zaptivenosti i propustljivosti ambalaţe, utvrĊivanja efikasnosti procesa sušenja, analize atmosfere proizvoda upakovanih u modifikovanoj atmosferi, praćenja sadrţaja gasa i pritiska na proizvodnoj liniji, praćenja fermentacionog procesa i praćenja i kontrole kontaminacije. Postoji nekoliko firmi koje se bave razvojem i proizvodnjom ureĊaja za industrijsko merenje sadrţaja gasa u prehrambenoj industriji, i to za odreĊivanje sadrţaja gasa u karboniziranim proizvodima, prozvodima punjenim u atmosferi azota i pasterizovanim ili toplopunjenim proizvodima. Prednosti primene TDLAS ureĊaja u prehrambenoj industriji su ekonomska isplatljivost (smanjivanje troškova investicija i odrţavanja), unapreĊenje kvaliteta proizvodnje i univerzalnost merenja nezavisno od vrste pakovanja i boje ambalaţe. Jedino ograniĉenje tehnike je propustljivost ambalaţe za laserski zrak, odnosno transparetnost od najmanje 5%.

Zbog jednostavnosti primene i osetljivosti, ureĊaji konstruisani na bazi TDLAS mogu se koristiti za odreĊivanje sadrţaja gasova u istraţivanjima. Tako, posebno razvijeni laboratorisjki ureĊaji pokazuju obećavajuće rezultate za kontinualno

merenje sadrţaja CO2 u upakovanim fermentisanim mleĉnim proizvodima. Takva istraţivanja mogu voditi uspostavljanju veze izmeĊu sadrţaja gasa i prisustva kontaminanata u mleĉnim proizvodima, a što bi pojednostavilo kontrolu i pomoglo utvrĊivanju stanja proizvoda u odnosu na kvarenje, kao i rok trajanja mleĉnih proizvoda.

Zahvalnica: Ovaj rad je rezultat projekta „PACKSENSOR‖ (1206.005-14 - http://www.cei.int/content/cei-kep-italy-packsensor-project-development) u okviru poziva ‗‘CEI - Central European Initiative‘‘

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6. Tunable Diode Laser Absorption Spectroscopy (TDLAS) (Online) http://nanoplus.com/en/technology/tunable-diode-laser-absorption-spectroscopy-tdlas/ (19.07.2016)

7. Linnerud, I., Kaspersen, P., Jaeger, T., Gas monitoring in the process industry using diode laser spectroscopy, Applied Physics B: Lasers and Optics, 67 (1998), 297-305.

8. P. Geiser, New Opportunities in Mid-Infrared Emission Control, Sensors, 2015, pp. 22724-22736. 9. FT System, (Online) http://www.ftsystem.com/english/prd-55-vacuum_pressure (21.07.2016) 10. GPX1000 Non-intrusive Oxygen Headspace Gas Analyser , (Online) http://gasporox.se/spot-check-

instruments (21.07.2016)

11. Food packaging industry, (Online) http://www.pd.ifn.cnr.it/technologies-transfer-activities/gas-sensing-activities/food-packaging-industry, (21.07.2016)

12. Cocola, L., M. Fedel, G. Tondello, L. Poletto: Optimization of the SAFETPACK in-line headspace oxygen analyzer for flow-packed products, 20th World Conference on Packaging, IAPRI2016, Proceedings (ISBN 978-85-7029-136-3) Campinas, Brasil, 12-15 June 2016. pp. 76-81.


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13. Teymori, R., Ghazanfarirad, N., Dehghan, K., Kheyri, A., Hajigholizadeh, G., Kazemi- Ghoshchi B., Bahmani, M., Monitoring microbial quality of commercial dairy products in West Azerbaijan province, northwest of Iran, Asian Pacific Journal of Tropical Disease, 4, (2014), S824-S829.

14. MacBean R.D., Packaging and the Shelf Life of Yogurt, in Food packaging and Shelf Life, Ed G.L. Roberts, CRC press, (2010), pp 143-156.

15. Global Food Losses and Food Waste, (online) http://www.fao.org/docrep/014/mb060e/mb060e00.pdf (30.07.2016)

16. Cocola, L., Fedel, M., Poletto, L., Tondello, G., Laser spectroscopy for totally non-intrusive detection of oxygen in modified atmosphere food package, Applied Physics B: Lasers and Optics, 119, (2015), 37-44.

17. Hotchkiss, H., Werner, G., Lee E., Addition of Carbon Dioxide to Dairy Products to Improve Quality: A Comprehensive Review, Comprehencive Reviews in Food Science and Food Safety, 5, (2006), 158-168.

18. Muniandya, P., Shorib, A., Babaa, A., Influence of green, white and black tea addition on the antioxidant activity of probiotic yogurt during refrigerated storage, Food Packaging and Shelf Life 8, (2016) 1–8.

19. Cocola, L., M. Fedel, D. Savić, B. Danilović, L. Poletto: Development and validation of a carbon dioxide TDLAS sensor for studies on fermented dairy products, 20th World Conference on Packaging, IAPRI2016, Proceedings

(ISBN 978-85-7029-136-3) Campinas, Brasil, 12-15 June 2016. pp. 82-88. 20. Sønderby, S., L. Cocola, H. Allermann, M. Fedel, J. P. Schreiber, G. Tondello, A. Bardenstein, L. Poletto:

Laboratory validation of new non-intrusive laser optical sensor of oxygen for in-line monitoring of food packaging headspace, Proceedings of 27th IAPRI Symposium on Packaging, Valencia, Spain, 8-11 June 2015, pp. 85-93.

21. Danilović, B., Cocola, L., Fedel, M., Poletto, L., Savić, D. Formation and cumulation of CO2 in the bottles of the fermented milk drinks, IPCBEE, 95 (2016), 26-31.

22. Danilović, B., L. Cocola, M. Fedel, L. Poletto, V. Lavrenĉić, D. Savić: Monitoring of the change of carbon dioxide concentration in headspace of packed fermented dairy products, The MacroTrend Conference on Medicine, Science, and Technology, Dubrovnik, Croatia, 30-31. july 2016., pp.33-34.

GAS CONTENT MEASUREMENT IN HEADSPACE OF FOOD PACKAGES ON NON-DESTRUCTIVE MANNER

Dragiša Savić1, Bojana Danilović1, Luca Poletto2

1Food Technology and Biotechnology Department, Faculty of Technology, Leskovac, University of Niš, Bulevar Oslobodjenja 124, 16000 Leskovac, Serbia. [email protected]

2CNR Institute for Photonics and Nanotechnologies, via Trasea 7, 35131 Padua, Italy, [email protected]

The paper reviewed the principles and industrial application of the measuring the concentration of gases (O2, H2O, CO2) in a contactless, non-invasive way inside food closed containers (bottles, cups…) in real time. The measurement is based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) with a Wavelength Modulation Spectroscopy with advantages of selectivity, non-invasivity and with no effect on the sample no matter of pressure, temperature and velocity of the sample. The method has been already applied in bottling industry (determination of O2 and CO2 in the sparkling wine and soft drink industry; leak detection with measurement of vacuum level in filling lines of juice products) as well as in analyzing modified atmosphere packages (fruits, cheeses). Beside that, the technique offer possibilities for determining the level of food spoilage by monitoring gas content in the packages since the majority of food spoilage microorganisms produce CO2. As consequence, CO2 level could be a good indicator to recognize contamination at an early stage, and O2 content is an indicator of the quality of the product and of the sealing process.

Key words: TDLAS, gas measurement, food packages


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TEXTILE PRINTING – PAST, PRESENT, FUTURE

Nemanja Kašiković1, Gojko Vladić2, Dragoljub Novaković2

1University of Novi Sad, Faculty of Technical Sciences, Department of Graphic Engineering and Design, [email protected]

2 University of Novi Sad, Faculty of Technical Sciences, Department of Graphic Engineering and Design, [email protected], [email protected]

ISSN 2232-755X UDC: 655.228:656.1

DOI: 10.7251GHTE16VI035K

Textile printing can be defined as the process of transferring ink to the textile substrates by using specific printing technique and machines. The most suitable techniques for textile substrates printing are: screen printing, digital ink-jet printing or usage of thermal transfer processes. In the past and today the most popular textile printing technique is a screen printing, with its advantages in terms of total costs and productivity, as well as simplicity and speed in high printing volumes. Also, screen printing machines usually cost less compared to the other printing techniques machines. On the other hand, digital ink jet textile printing offers higher printing speed of short runs, flexibility, creativity and environmental benefits. In addition, it is important to note that using digital printing techniques enables better visual effects, as well as wider flexibility of print formats. Besides that, it offers better control of print quality uniformity during the production runs. The aim of this paper is to compare these two techniques and to predict future developments in this field.

Key words: textile printing, screen printing, digital printing

INTRODUCTION

A printing process can be defined as the localized application of the colorant to the selected areas of the substrate. Besides printing, a dyeing of the textiles is often used in industrial applications. The difference between those two processes is that instead of uniformed coloring of the whole surface of the substrate in case of dying process, by printing, a color is applied only to the target areas, thus introducing various colors, patterns, and designs to the textile fabrics. Although today printing is almost synonymous to paper printing, first printing techniques were used for textile printing and only later adapted for more precise paper printing. The oldest printed textiles which survived to these days are China‘s three color silk prints, dated back to 220 BCE, while, according to Brunello, the earliest dyed cotton

was found in the Indus valley originating from around 3000 BCE [1].

The textile printing methods can be divided into three basic methods: • Direct printing method, • Discharge printing method and • Resist printing method.

In the direct printing method, which is predominant printing method today, the color carrying pigment or dye (usually in the paste form) is applied onto the fabric by impression. The impression can be achieved in various ways, which will be explained later in this chapter. Woodblock printing originating in China is the oldest known direct printing method. The relief pattern engraved by wood engraving xylography tool (knife or chisel) serves as the printing areas, which stays at the original surface level of the initial wood material. The image would be printed from the pattern as the mirror-image, by placing woodblock on top of the fabric and applying the pressure. The process and typical result are illustrated in Fig 1. Multicolor prints were achieved by using multiple blocks, each for one color. This technique is still extensively used in its traditional form in countries like India, producing one-off designs. Direct printing method was used first and still is the most frequently used method for textile printing. The most modern digital NIP (Non-Impact Printing) processes are also considered to be direct printing methods.

N. Kašiković i sar.: TEXTILE PRINTING – PAST, PRESENT, FUTURE

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Figure 1. The woodblock printing

Discharge printing, also known as extract printing, is a method based on the chemical destruction of the color in the

selected areas. The fabric must be dyed before the process, a design is applied to the dyed fabric by printing a color-destroying agent (chlorine, hydrosulfite, etc.), thus bleaching out a pattern on the colored fabric. For the production of a colored design, the dye resistant to the color-destroying agent can be added. The color-destroying agent can be applied by a wide variety of printing techniques, where the screen printing is the most popular today. A typical result of discharge printed fabric is shown in Fig 2.

Figure 2. The result of discharge printed design

In the resist printing method, a bleached fabric is first printed with resist paste which prohibits the penetration of the dye into the fabric. The fabric is then dyed and subsequently the resist paste is removed leaving the desired pattern. Multicolor pattern can be achieved by applying the paste which contains a substance resistant to second dye, on the already dyed cloth. This ensures a new color retention only in the areas uncovered by the paste. The process in which the pattern area is covered with wax is called batik. Besides batik method there is also a manual tie-dyeing method in which patterns are produced by tying together the gathered cloth, using string, before immersing it in the dye bath, thus preventing the dye to penetrate the tied sections. The cloth tying and the typical result of the process are shown in Fig 3.

Figure 3. Cloth tying and typical result of tie-die method


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FUNDAMENTALS OF TEXTILE SCREEN PRINTING

Screen printing is an extension of stencil printing, which originated in Japan during 17th and 18th century. It evolved from Kata-gami paper stencils, and the method was used worldwide by the 19th century [2, 3].

Woven silk fabric as a continuous support for the paper stencil was introduced in the second half of the 19th century, not long after the durable paint replaced paper stencil on the screen fabric. Accurate multicolor printing was enabled by further improvements of the screens using silk, cotton, viscose rayon and cellulose diacetate, which ensured stable screens with non-water based print pastes. Later, the hydrophobic synthetic materials, such as nylon and polyester, in combination with metal frames instead of wooden ones were introduced. This allowed greater tension of the fabric when stretched over the frame, ensuring constant tension during the printing. The process of flat-screen printing was mechanized and fully automated by the half of the 20th century. Also, improvements were made in dryers, UV curable inks were introduced, which popularized screen printing technique even more. Continuous screen printing was achieved using rotary screen printing presses that allowed much higher printing speeds and simultaneous printing of both fabric sides. Currently, rotary screen printing is the predominant textile printing method [4].

Due to its nature, screen printing uses much lower printing pressure compared to the other direct printing techniques. This allows greater ink volume to be transferred while maintaining precision (ink is not pushed into the fabric structure which improves color strength and maintains textured surface of the fabric). Utilization of relatively cheap and simple

process as well as the simplicity of the machinery used throughout, allows a wider range of inks and dyes to be used in the screen printing technique, more than in any other known printing technology.

Screen printing process is based on forcing the ink through the openings in a fine screen mesh. Non-printing areas are covered by the stencil, which blocks the ink from passing through the screen onto the substrate material surface.

The screen printing process typically consists of five prerequisite elements that ensure reproducible prints:

• Suitable printing medium (printing ink), • Mesh screen with a stencil design (containing the artwork), • Flexible and resilient squeegee, • Printing substrate (textile fabric), • Base blanket or cylinder (ensures positioning of the substrate).

Integration of the above mentioned prerequisites ensures controlled transfer of the ink, through the openings in the mesh onto the printing substrate. The surface of the screen must not be in contact with the substrate, because it could create an unclean or damaged print due to uncontrollable substrate snap off from the screen. The contact only occurs when the squeegee applies pressure, forcing the ink through the open areas of the screen mesh in a controlled manner, Fig 4.

Figure 4. Screen printing principle

In practice, two basic screen printing methods are used for textile printing:

A flat-to-flat (flatbed) printing, where both the screen printing mesh that is attached to the rectangular frame, and the printing substrate are flat, Fig 5 a. Printed image in this printing method is limited by the size of the frame and it is usually used for printing of smaller areas on garments (T-shirts, jackets, etc.), although it is possible to produce prints

of up to 8 square meters. Printing on a curved surface is also possible, but it is not often used for textile printing. The printing plate is flat, while the printing substrate is fixed on a rotating cylinder, Fig 5 b.

In round-to-round printing method (rotary printing), the printing plate (screen with the stencil) and the pressure element are cylinders which rotate synchronously. The printing substrate, usually continues the role of fabric, is nipped between the screen and the pressure cylinder. Ink is transferred from the inside of the cylindrical printing plate, Fig 5 c.


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Fig 5 Screen printing methods: (a) Flat-to-flat method (flatbed). (b) Screen printing on a curved surface. (c) Round-to-round method (rotary printing) [5]

Printing mediums (ink) suitable for screen printing on textile substrates are extremely versatile. A short overview of inks is given to provide a rough idea of how flexible the process is and to show wide possibilities for different effects.

Plastisol inks are PCV based and most commonly used for textile printing, giving the attractive, clear and vibrant color, with good opacity resulting in very fine prints.

Water-based inks are also often used for textile printing. Water based solvent inside these inks ensures that pigments can penetrate the fabric resulting in more durable prints that are soft to the touch.

Puff inks are plastisol inks with additives which raise the print off the fabric surface creating the 3D effects. Similarly, metallic flakes can be suspended in the plastisol ink creating the sparkling glitter effect. In addition to the wide variety of inks, effects can be achieved also by adding the additional layer of emulsion to the screen resulting in thicker ink deposition.

Flocking is a two-step process, where plastisol adhesive is printed and then a small rayon fiber particles are applied resulting in velvet textured finish.

Similarly, after printing a plastisol adhesive, metallic foil can be applied using heat-press.

Screen printing can be used also for application of color-destroying agent in discharge dying method or enzyme based paste in burnout process.

The screen stencil plays the most important role in screen printing process and it must be optimally suited for the print

job. Relevant factors to consider are characteristics of the screen mesh, photo emulsion, coating technique and parameters of the exposure process.

Alongside the material that stencil can be made of (cotton, silk, nylon, mono- and multifilament polyester, metal), selection of the proper mesh count (number of threads per cm) and thread thickness are the most important parameters as they determine open screen area and consequently the amount of ink that will be deposited, as well as the amount of details the screen can support [5, 6].

Schematic of a mesh opening is shown in Fig 6. The open screen area can be calculated by equation 1.

(1)

Figure 6. Schematic of a mesh opening


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The screen mesh is available from 10 up to 200 threads/cm. The higher mesh count allows reproduction of finer details, but also reduces the amount of ink deposited. The screen mesh is mounted on the frame by adhesives or staples, depending on the frame material. Wooden frames are commonly used because of their low price, and simple manufacturing process. However, they also have many drawbacks: they are not very stable, thus they are usually used only for single color printing and relatively small format print jobs [7].

Steel and aluminum are usually used for screen printing frames almost exclusively in the professional screen printing. Metal frames have much better stability than wooden ones, which is very important for print formats larger than 50 cm and multi-color printing, which demands precise color registration [7].

The correct screen tension is an important factor in achieving high print quality, particularly regarding multicolor printing. Screen tension depends on the material, fabric count, fabric quality, and yield point they determine. Usual screen tension is in the range of 0-25 N/cm. The tension that has been applied to the screen mesh diminishes over the time in relation to the nature of the screen fabric, adhesion technology employed and stress deployed during printing process. In the case of certain synthetic fabrics, tension can diminish up to 50% after just two days [6].

Rotary screen printing machines use the screens manufactured by electrodeposition of nickel and milling process, producing a uniform spiral pattern of hexagonal holes with no seam, in the case of Lacquer screens. These screens are course and cannot achieve fine line work such as screen meshes for flatbed printing. Galvano screens are also produced by electrodepositing but the printing and non-printing areas are defined directly in the screen making

process. Non-printing areas are solid nickel, instead of a uniform mesh filled with a thin layer of lacquer, which makes these screens much stronger than Lacquer screens [4].

The squeegee is a rubber or plastic blade, fixed to the handle for manual printing or to a clamp in mechanized screen printing. It is used to force the ink into and through the open areas of the screen stencil. By pushing the screen onto the substrate squeegee adjusts the screen to the surface of the substrate material, controls the spread of ink across the screen and it also removes the excessive ink from the mesh. The thickness of the printed ink film and the print quality is controlled by many factors such as composition, size and form, angle, pressure, and speed of the squeegee.

Squeegees are categorized by their hardness, which is measured by a durometer gauge based on standards established by American Standard Testing materials (ASTM). Squeegees used for screen printing on textile substrates are extra soft (45-50 Shore A) and soft (50-60 Shore A).

FUNDAMENTALS OF TEXTILE DIGITAL PRINTING

The most commonly used digital printing technology for textile printing is ink jet. The ink jet process is a computer to print technology in which ink is sprayed from nozzles, which means that no printing master is needed and the imaging

is done directly onto the substrate [6].

Ink jet technologies could be divided in two main groups: Continuous Ink Jet (CIJ) and Drop-on-Demand Ink Jet (DOD). Continuous ink jet is typically subdivided in binary deflection and multi-deflection category. On the other hand, Drop on Demand Ink Jet can be subdivided into the process variations of thermal, piezo and electrostatic ink jet.

The difference between this processes is that in the continuous ink jet, only a part of the continuously generated flow of small ink drops is directed onto the substrate during printing in accordance with the image signal. The unprinted droplets are collected and returned for reuse [8].

In a drop on demand ink jet processes, drops of ink are only generated if the information to be printed requires them.

The beginning of continuous ink jet printing process is connected with Sweet at Stanford University (mid-1960s). In this process, the ink is driven through nozzles that eject a continuous stream of uniformly spaced and sized droplets at high frequency by the vibration of piezo crystals [8-12].

In Continuous ink jet, the jet of ink generated by each nozzle breaks up into droplets shortly after exiting the nozzle. Without any other intervention, the breakup would occur randomly and would result in droplets of variable sizes. This is usually corrected by providing a periodic excitation to the nozzle in the time domain that translates into a spatial perturbation in the jet of fluid. The combination of the jet velocity and frequency of the excitation determines the droplet size, which can be controlled to very high accuracy [13].

In the traditional Continuous ink jet approach, a piezoelectric transducer is coupled to the print head to provide the periodic excitation. The oscillations are therefore mechanical in nature. After leaving the nozzle, the drops are electrically charged by an amount that depends on the image to be printed. The drops then pass through an electric field to enable their deflection [13]. There are two ways of deflecting the drops in piezoelectric-driven CIJ: binary deflection and multi-deflection.

In Fig 7 is presented one example of binary deflection process, where the drop has one of two charge states (namely uncharged for conveyance to the paper and charged for deflection in an electrical field). The uncharged droplets are ejected directly to the substrate, while the charged droplets are recycled into the printing system [14].


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In the multi-deflection process, the droplets receive different electrical charges and are diverted onto the substrate at different angles. The uncharged droplets return to a gutter to be re-circulated (Fig 8).

Also, in Continuous Ink Jet, there is a system called the Hertz printing method, which was presented in 1966. by Dr. Carl H. Hertz [15]. In this method, the density of printed ink per pixel is variable. This is achieved by generating very small drops (of the order of 3 pl) at speeds of about 40 m/s with excitation frequencies of over 1MHz. The drops not intended to reach the medium are charged and deflected to a gutter [13].

There is another CIJ printing method known as a Microdot CIJ printing, in which the drops with different diameters are produced, but only the smaller drops are selectively charged and deflected to the substrate [16].

Generally, we can say that droplets in this process have large diameter (approximately 40 µm) and that is the reason why the print resolution is relatively low. This process is generally used in industrial applications, but it is not dominant ink jet process in textile printing.

Figure 7. Functioning principle of continuous ink jet technology – binary deflection

Figure 8. Functioning principle of continuous ink jet technology – multi-deflection

A good example of using Continuous Ink Jet process in textile printing is OSIRIS textile printer, Fig 9. This printing system is an excellent choice for printing of fashion and interior decoration fabrics with unrivaled productivity, reliability, and cost per meter, providing an excellent solution for lower cost digital textile printing, for short runs, but for longer runs as well.

That system uses the multi-deflection continuous ink jet technology, which produces, controls and directs approx 224.000.000 droplets, with a placement accuracy of max. 20 microns. Production speed of this machine is 18-30 m/min, with up to 12 printing positions, called ―beams‖, each consisting of a fixed array of 48 to 56 ink jet heads.

Maximum printing width is 3.2 m, while the machine can print fashion substrates from 24 g/m2 to 33 g/m2, and for special applications substrates of up to 264 g/m2. That means that this printing system can print most substrate types from very light silk to a heavy weight viscose.


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Figure 9. OSIRIS textile printer – printing unit [17]

Examples of the products printed on OSIRIS printing machine are presented in Fig 10.

a) b)

c)

Figure 10. Samples printed by OSIRIS textile printer [17]

The Drop on demand Ink Jet process was invented by Siemens in 1977. The first drop on demand technique was thermal drop on demand ink jet technique. Except thermal, the other two techniques that fall into the same, drop on demand category are piezoelectric [18-20] and electrostatic [21]. The difference between these techniques is the way they generate a pressure pulse, because in this type of ink jet printing system, droplets are ejected from the nozzles by pressure pulse created only when it is necessary [18-20]. In thermal ink jet process, a drop can be generated by heat transfer, while in piezoelectric process drop is generated by changing the chamber volume in a nozzle channel and in the electrostatic ink jet method, the droplets ejection through the nozzles is induced by electrostatic forces.

The sequences of Piezo Ink Jet Printing Process in Fig 11 show in a simplified form how an ink drop can be ejected as a result of ejection of an ink drop by mechanical displacement in the ink channel [22].

Figure 11. Functioning principle of drop on demand ink jet technology – piezo ink jet


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Piezo element is typically made of lead zirconate titanate (PZT). The piezo transducer could be attached to a membrane that forms an ink chamber wall or could actually constitute the chamber itself. In both cases, the volume of the chamber is reduced, and the ink droplet is ejected from the nozzle [13].

Piezo-ceramic materials are ideally suited for small, electrically addressable systems [6], but depending of their deformation, piezo ink jet printing technology could be classified as bend (Tektroni, Epson, Biofluidix printheads), push (Hitachi, Dataproducts, Epson, Biofluidix printheads), shear (Tektronix, Sharp, Xaar printheads), and squeeze (Microdrop, Microfab printheads) [23]. Common characteristics for all these modes are that the print heads are heat resistance, spacing of droplets can be controlled by angling the line of nozzles along the print head, and the most important feature is that the speed, size, and shape of the droplets can be controlled by adjusting the waveform of voltage applied to the nozzles.

A lot of companies produces piezo ink jet printing systems. For example Brother, Epson, Fujifilm Dimatix, Konica Minolta, Kyocera, Panasonic, Ricoh, SII Printek, Toshiba Tec, Trident, Xaar Xerox etc. This technique could be used in a very wide range of applications, not only for textile products.

With this system we have adaptable configurations to provide higher speeds and print quality, consistent drop velocity and drop volume, wide range of ink capability, high accuracy jetting, long-life print heads, etc. If we speak about print heads, today on the market we can find different print heads like Epson DX5 Series print head, Fujifilm Polaris PQ-512/15 AAA, Fujifilm Dimatix StarFire SG1024, StarFire SG-1024/M-C, Konica Minolta 512, Konica Minolta 1024i Series,

Kyocera KJ4B-QA, Ricoh GEN5, etc.

In the continuation of this section different examples of ink jet printing machines are presented (Figs 12, 13).

Figure 12. Mimaki JV 22 – 160 Figure 13. Polyprint TexJet

With thermal drop on demand ink jet, unlike piezo drop on demand, ejection of an ink drop is generated by heating and vaporization within the ink jet system (Fig 14).

Figure 14. Working principle of drop on demand ink jet technology – thermal ink jet

The droplets are formed within a few microseconds, where the temperature is rapidly raised to 300 - 400 0C (in order to evaporate the ink) using resistive element. High temperature and resulting ink evaporation creates a bubble which forces the ink out of the nozzles (Le, 1998). After droplets are ejected, an ink chamber is filled with fresh ink and the process can be repeated [8].

The print heads made for this ink jet process type are not expensive and the very important thing is that they have the ability to create small-size droplets, although have certain limitations on the use of fluids in ink formulation. The fluids not only have to be able to vaporize (aqueous solution), but they must also withstand ultra-high temperatures [8].

Thermal ink jet process has several configurations of drop ejectors. The most popular are 'roof-shooter' (HewlettePackard, Lexmark, and Olivetti) and 'side-shooter' types (Canon and Xerox) - depending on the heater


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position, although in some printing machines we can find 'back-shooter', multi heater, double heater, suspended heater and movable member drop generator design.

This process is not so widespread as piezo ink jet process, where only several companies manufacture this machine type (Canon, HP, Olivetti, Lexmark, Xerox). Firms like Cannon, HP, Lexmark and Memjet produce very quality thermal print heads.

Canon has developed a specific type of thermal print head, known as ‘bubble jet‘ As well, it mastered a technique of print head manufacturing known as Full-Photolithography Inkjet Nozzle Engineering (FINE). This patented Canon process enables the manufacturing of high-density print heads with exceptional precision. Whereas typical thermal print heads have a maximum of only 600 nozzles. Canon produces print heads for image PROGRAF printers with a total of 15,360 nozzles.

Unfortunately, Canon did not find still adequate solution for textile printing.

On the other hand, HP has invested significant funds in improving their thermal heads. One of the effects of this high R&D investments is textile printing machine, HP Latex Series (Fig 15). HP Latex Inks and HP Thermal Inkjet Technology provide durable, odorless prints, sharp, vivid image quality, application versatility, and a high productivity.

Figure 15. HP Latex 3100 ink jet printing machine [23]

In electrostatic drop on demand ink jet printing process (Fig 27), an electrical field between the nozzles and the substrate is generated. The ink drops are produced by sending image-dependent control impulses to the nozzles. These impulses cause an ink drop to be released and routed through the electrical field onto the substrate [6].

Figure 16. Functioning principle of drop on demand ink jet technology – electrostatic ink jet

Unfortunatly, electrostatic ink jet printing is not yet in use for textile printing.


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FUNDAMENTALS OF TRANSFER PRINTING PROCESS

The process in which the design is firstly printed onto a flexible, non-textile substrate, and later on transferred by a separate process onto a textile material, is called transfer printing. One of the examples of transfer printing is presented in Fig 17 as well as a heating element for transfer of a design from a paper onto a textile substrate (Fig 18).

Figure 17. The usage of ink jet printing process in transfer printing process

Figure 18. Heat element for heat transfer of design from paper onto a textile substrate

Transfer printing process could be divided on sublimation transfer, melt transfer, film release and wet transfer.

The most popular transfer printing process is sublimation transfer, which depends on the use of a volatile dye in the printed design. When the paper is heated, the dye is preferentially adsorbed from the vapor phase by the textile material in which the heated paper is in contact.

The oldest transfer printing technique is melt transfer. It has been used since the 19th century to transfer embroidery designs to fabric. In melt transfer, the design is printed on a substrate using a waxy ink, and then a hot iron is applied to its reverse face which presses the paper against the fabric. The ink melts onto the fabric.

Film release process is similar to melt transfer. The only difference is that the design is held in an ink layer which is transferred completely to the textile from a release paper using heat and pressure. Generated adhesion forces between the film and the textile are stronger than those between the film and the paper. The method has been developed for printing of both continuous web and garment panel units, but is used almost exclusively for the latter

purpose [24].

Water-soluble dyes are incorporated into a printing ink which is used to produce a design on a paper. The design is transferred to a moist textile using carefully regulated contact pressure. The dye transfers by diffusion through the aqueous medium. The method is not used extensively [24].

The reasons why this technique is still popular are numerous. The production of short runs and repeated orders is much easier to produce, sometimes it is easier to produce complex design on the paper than on the textile, designs could be printed on cheap substrate before the transfer to the more expensive textile materials, and sometimes this is the only way to make certain special effects on garments or garment panels. As well the designs that are on paper, decreases both storage space and costs, relatively cheap equipment is needed (machines, irons, etc.), and the design may be applied to the textiles with relatively low skill input and low reject rates [24].


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The problem with this is that no single transfer-printing method is universally applicable to a wide range of textile fibers. While a printer with a conventional rotary-screen printing set-up can print cotton, polyester, blends and so forth without doing a great deal beyond changing the printing ink used, the transfer printer hoping to have the same flexibility would need to have available a wide range of equipment suited to the variety of systems that have to be used for different dyes and substrates that use transfer technology [24].

CONCLUSION

Screen Printing vs Digital Printing

Comparison between conventional screen printing and digital printing is an ongoing debate, because we are in the transition period where both technologies have specific niche of dominance. The tools redundancy for the digital printing process is big advantage of digital printing technique, as the screen printing process involves making a stencil, fixing it to the machine, spreading the ink mechanically, while on the other hand only a computer and a printer with ink cartridges are needed for digital printing process. Screen printing still offers better print quality as it gives clearer edges, the ink gets deeply absorbed and lasts longer, while CMYK reproductions possess far better quality regarding digital printing. Multiple screens needed for more complex artwork, and preparation process makes the screen printing more expensive for short runs, but as the print run volumes exceed a few dozen copies, the costs are relatively the

same. In high volume runs, screen printing technique is far more cost effective as the price drops with each copy, while in the case of digital printing, cost for each print is the same, regardless the circulation.

Acknowledgements

This chapter was supported by the Serbian Ministry of Science and Technological Development, Grant No.: 35027 ―The development of software model for improvement of knowledge and production in graphic arts industry.‖

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ŠTAMPA NA TEKSTILU – PROŠLOST, SADAŠNJOST, BUDUĆNOST

Nemanja Kašiković1, Gojko Vladić2, Dragoljub Novaković2

1Univerzitet u Novom Sadu, Fakultet tehniĉkih nauka, Departman za grafiĉko inţenjerstvo i dizajn, [email protected]

2Univerzitet u Novom Sadu, Fakultet tehniĉkih nauka, Departman za grafiĉko inţenjerstvo i dizajn, [email protected], [email protected]

Proces štampe na tekstil moţe se definisati kao proces u kom se boja nanosi na tekstilnu podlogu primenom razliĉitih tehnika i mašina. Najpogodnije tehnike za štampu na ovim materijalima su tehnike sito i digitalne štampe, kao i primena termo transfer procesa. Tehniku sito štampe, koja je najzastupljenija tehnika štampe na tekstilu, karakterišu niski troškovi, visoka produktivnost i jednostavnost procesa, što je naroĉito izraţeno pri štampi većih tiraţa. Nije zanemarljivo ni to što su cene ovih mašina mnogo niţe u odnosu na mašine koje koriste druge princpe štampanja. Sa druge strane, digitalni postupak štampe na tekstilne podloge nudi veću brzinu i niţu cenu kod malih tiraţa, kao i fleksibilnost, kreativnost i zaštitu ţivotne sredine zbog manje upotrebe hemikalija. Digitalnu tehniku štampe karakteriše i mogućnost dobijanja boljih vizuelnih efekata, veća fleksibilnost pri odabiru podloga za štampu, kao i ujednaĉen kvalitet otiska za vreme proizvodnje. Cilj ovog rada je da se da uporedni prikaz ove dve tehnike i da se da predviĊanje o budućim trendovima na trţištu.

Kljuĉne reĉi: štampa na tekstil, sito štampa, digitalna štampa

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