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THE USE OF CLAY AS ADSORBENT AND COAGULANT AID IN
TEXTILE WASTEWATER TREATMENT
Andita Rachmania Dwipayani
1
, Suprihanto Notodarmojo
2
, and Qomarudin Helmy
3
Graduate Program of Environmental EngineeringFaculty of Civil and Environmental Engineering, Institut Teknologi Bandung
Jl. Ganesha No. 10, Bandung 401321andita.rachmania@gmail.com, 2suprihanto@ftsl.itb.ac.id, 3kihelmy@yahoo.com
Abstract: There are two sub researches that are conducted in this research, both researches were done batch atthe room temperature. The first sub research is analysis of adsorption capability of clays for organic
compounds removal (COD) from textile wastewater. In this research, the variables that examined were
wastewater pH level, dosages of clays, and contact time on adsorption process. The wastewater that used were
originated from effluents of textile production units with concentration of COD approximately 230-285 mg/L.
The purpose of this research was to obtain the optimum conditions for the ability of both kinds of clays to
remove COD parameter of waste water. After the optimum condition was obtained, analysis then carried out tothe determination of adsorption kinetics for COD removal, using Langmuir and Freundlich isotherm models.
Optimum conditions on the use of Arcamanik and Dago clays were at pH 7 and the dose of clays of 15 gr/L and
30 mg/L. COD removal reaches its stagnant level at the contact time of 120 minutes. At this condition, COD
removal for Arcamanik and Dago clay reach 48.5% and 26.65%. Factors that affect the clays capability as
adsorbent are associated by the morphological properties of clay. The second sub research is clays potential as
coagulant aid for COD removal. The research variables that were conducted were variation of dosages of clay
and wastewater pH level. For the use of 30 mg/L of alum coagulant, the addition of 30 mg/L of Arcamanik clay
was able to improve the COD removal efficiency from 8.95% to 13.43%, while the use of Dago clays generate
the COD removal to 16,98%. But this COD removal efficiency level was still lower than one with the use of 40
mg/L of alum, that is 17.9%.
Keywords: textile wastewater, COD, clays, adsorption, coagulant aid.
INTRODUCTIONTextile industry is one of the industries that has rapid development in Indonesia.
Textile industrys production process consists of the process of desizing, bleaching, dryingand coloring. Textile fabric staining process produces waste that has been known containschemical compounds, surfactants, dissolved solids, and probably contains heavy metals likeCr, Ni, and Cu (Kannan and Sundaram, 2001).
In general, wastewater treatment can be conducted physically, chemistry, andbiologically. But chemical, physical, and biology processes which commonly applied oftenbecome less effective because the more complex the waste that is produced and the high
operational cost (Sugiarto, 2002 in Hadiwidodo,et al., 2009).One of the common applications of physical treatment is the coagulation andflocculation process. Coagulation and flocculation processes include the addition of chemicalcompounds and agitation that make colloidal particles destabilized which form flocks that arecapable to precipitate. The chemical compound that is added called coagulant.
To improve the performance of the process of coagulation, the common thing thatusually done is the addition of other compounds, called coagulant aid. Coagulant aid thatcommonly used are chemical compounds of the polymer. Beside of its function to improvethe coagulation performance, the addition of coagulant aid also aims to reduce the use ofchemical coagulant (alum, lime, ferro sulphate) required. However, the most abundant
polymer compounds used as coagulant aid have a high selling price in the market.
One way to improve the coagulation performance is to do a combination with otherprocess, such adsorption. Adsorption is the process of centralizing the molecule or ion
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adsorbate on surface layer of adsorbent, either physically or chemically (Muhdarina, et al.,2010). Adsorption is a process that has good prospects in the textiles wastewater treatment
process (Robinson, et al., 2001; Kamel, et al., 1991; in Mumin, et al., 2007).Research on combination of coagulation-adsorption process has been done, one
example by Shen and Chaung (1998). In this study, they use polydially dimethyil ammonium
chloride (PPDAC) coagulant and activated carbon adsorbents of 100 mesh-size. Conclusionsof this research was that the addition of carbon adsorbents on the coagulation process provedeffective in the removal of dissolved organic carbon compounds because each process is ableto cover each other's deficiencies. Organic compounds that were removed by the process ofcoagulation were compounds with high molecular weight and have a negative charge. Whilethe use of activated carbon more effectively to adsorp compounds with small molecularweights and are uncharged.
This research aims to find alternative materials that can be used as substitution forchemical coagulant aid, especially in removal of organic compound in wastewater. Onematerial that has abundant availability in nature with relatively low price is clay. In the use ofclay for wastewater treatment, clays are generaly classified as adsorbent, because they have
adsorption ability due to their surface area (Al-Jlil and Alsewailem, 2009; Errais, et al., 2012;Liu and Zhang, 2007).
The type of clay that commonly used as nano-adsorbent are montmorilonite/smectiteand kaolinite (Liu, et al., 2007). Previous researched that conducted by Adebowale, et al(2006) about adsorption of metals ion by clay showed that adsorption of metals increased bythe addition of initial concentration of metals, pH, and adsorbent dosages (Al-Jlil, et al.,2009).
METHODOLOGYThis research consists of two sub researches which in practice include several stages,
they are: the initial textile waste characterization and analysis of morphology of clays, clayadsorption capability analysis, and analysis of the ability of clay as a coagulant aid.
Initial characterization of the textile waste and morphologic analysis of clays
This stage consists of analysis of mineral and morphology of clays, and the initialtextile wastewater quality. Parameters measured for wastewater quality are mentioned inWest Java Decree No. 6/1999 on quality standards for textile industry wastewater. These
parameters include: BOD, COD, TSS, Total phenol, Chromium (Cr), oil and grease, and pH.While one example of the analysis of the mineral content and morphology of clays isconducted from XRD and BET surface analysis.
Adsorption Analysis of Clays
The process of adsorption was done in batch for both kinds of clays. The adsorptionanalysis conducted through the variation of pH level of wastewater, dosages of clays, andcontact time, those are done gradually. At first, clays used were pounded and sifted soacquired the clays in desired size. The purpose of this analysis is to determine the optimumconditions of the adsorption capacity for both kinds of clays for the removal of COD oftextile wastewater.
Analysis of clays after adsorption process
At the end of adsorption process, the clays that were used then analysed theirmorphological and composition to be compared with their initial condition before treated asadsorbent. Morphological analysis of clays performed with SEM (Scanning ElectronMicroscopy) and FTIR (Fourier Transform Infrared Spectroscopy).
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Analysis of clays as coagulant aid
This study aimed to compare the removal efficiency of COD with and without theaddition of clay into the coagulation system. Research variables taken include: variation ofclays used and the variation dosages of clays. Of these variables, the optimum conditions forthe use of clays are then compared to the one without the addition of clays.
Data Analysis
To describe the mechanisms of adsorption, there are two types of isotherm models thatcan be used: Langmuir and Freundlich isotherm (Fair, et al., 1968). Langmuir isotherm formdisplayed on the equation. 1 while the equation for Freundlich isotherm is shown onequation. 2.
= +
(equation. 1)
log= log+ log (equation. 2)
q is the mass of a substance per unit weight of adsorbent (mg/g), Ceis the concentrationof a substance in equilibrium point, KL is the Langmuir constants, Kf is the Freundlich
constants, andis a factor of heterogeneity. Freundlich isotherm has been used extensively
by researchers as a simple way to analyze the adsorption of organic compounds (Joseph, etal., 1993).
RESULTS AND DISCUSSIONSWastewater quality
The wastewater that used came from the effluents of a production unit of the textileindustry in Bandung (PT. X). Analysis of the quality of the initial waste were done based on
the raw quality of textile waste that is set in Governor of West Java Decree No. 6/1999.Results of the analysis are shown in Table 1.
The high values of organic parameters, namely COD and BOD indicates that the wastewater has a high organic content, which is possibly derived from a substance used in the
production process. Aside from the process of coloring, the high concentration of organicpolluters come from wet process in the production of fabrics, which include the desizing,bleaching, and scouring processes (Komarawidjaja, 2007).
Table 1. Wastewater Quality Result
No Parameters of
AnalysisUnit Method
Maximum
Level*Analysis Result
1 BOD mg/L SMEWW 5210-B 60 1252 COD mg/L SMEWW 5220-B 150 281.63 TSS mg/L SMEWW 2540-D 50 1024 Fenol mg/L SMEWW 5530-C 0.5 0.2145 Total Chromium (Cr) mg/L SMEWW 3500-Cr 1.0 0.0886 Oil & Grease mg/L SMEWW 5520-D 3.0 12.47 pH - SMEWW 4500-H+ 6.0 9.0 7.38
*Quality standards refers to Governor of West Java Decree No. 6/1999
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The characteristics of adsorbent
The clays characteristics analysis includes morphological analysis and mineral contentof the clay. The XRD analysis for the clays mineral composition results shown in Tables 2and 3.
Table 2. Mineral Composition of Dago Clay.
Mineral Composition Chemical Formula
Quartz SiO2Kaolinite Al2Si2O5(OH)4
Muscovite (K, Na) Al2(Si, Al)4O10
Table 3. Mineral Composition of Arcamanik Clay
Mineral Composition Chemical Formula
Kaolinite Al2Si2O5(OH)4Albite, calcian, ordere (Na, Ca) Al (Si, Al)3O8
Muscovite (K, Na) Al2(Si, Al)4O10Cristobalite SiO
2
Montmorillonite CaO2(Al, Mg)2Si4O10(OH)
Clay mineralogy is typically monotonous: kaolinite, gibbsite, hematite, goethite,maghemite and Ti minerals (mainly ilmenite and anatase) are the prominent mineral phasesin the clay fraction (Schaefer, et al., 2008). It can be seen that in general, both types of clayused have a type of kaolinite minerals. The kaolinite minerals are known for its ability toform stable dispersions and to improve the properties of the material (Kogure, et al.,2010).
Kaolinite group has properties such as: easily to expands or shrinks, and difficult todestroy (stable) (Notodarmojo, 2005). Besides kaolinite group, there is also the content ofmontmorillonite which belong to the group of minerals smectite. Smectite minerals have a
negative charge which causes minerals are very reactive (Nilawati, 2013).The surface area of adsorbents is one of the important parameters for the interpretationof the sorption mechanism of organic compounds (Jonge and Mittelmeijer-Hazeleger, 1996).The large surface area of adsorbent enhance the possibility of sorbate to be adsorbed throughthe surface of adsorben, thus may increase the adsorbent activity (Nilawati, 2013).
Determination of the surface area of adsorbent was done with BET (Brunauer-Emmett-Teller) analysis method towards both of clays that were used. The analysis result shown onTable 4.
Table 4. Surface Area, Volume, and Diameter of Dago Clay and Arcamanik Clay
Parameters Dago Clay Arcamanik Clay
Surface area (m /g) 35.987 84.923
Total pore volume (cc/g)9.981 x 10-2
For pores smaller than4204.9 * (diameter)
1.629 x 10-1For pores smaller than2257.1 * (diameter)
Average pore diameter 1.10936 x 10 7.67151 x 10 *1 = 10-7mm
From Table 4, it can be seen that surface area of Arcamanik clay is wider than Dagoclay, which accompanied by smaller size of average pore diameter. This result correspondwith the theory stated by Notodarmojo (2005), that the more subtle or the smaller thediameter particles of a material, the wider the specific surface area.
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The influence of pH to the adsorption of the organic compounds
This experiment carried out analysis of the removal efficiency of organic substanceparameters (COD) of the variation of pH of wastewater, at pH 4, 5, 6, 7, 8, and 9. For bothtypes of clays, Adsorbent added as much as 2.5 gr/L. The process of adsorption was done in
batches for 120 minutes. The results shown in Figure 1.
Figure 1. The Influence of pH on The COD Removal Efficiency in Textile Waste Waterin Adsorption Process Using Clays (Dago and Arcamanik Clays).
On the use of Arcamanik clay, pH level of wastewater variation of 4, 5, 6, 7, 8, and 9generate COD removal efficiency of 32.76%; 32.76%; 35.51%; 43.96%; 38.36%; and35.56%. While the use of Dago clay generate the COD removal efficiency towards the samevariations of pH are: 27.74%; 19.4%; 19.4%; 47.19%; 36.07%; and 11.06%.
This result are correspond to some adsorption researches, one example were conductedby Liu and Zhang (2007), where adsorption with montmorillonit clay generate the highestCOD removal on neutral pH. Adsorption capacity decreases with the increasing pH level,except on neutral pH (Liu and Zhang, 2007). The research conducted by Scrudato and Estes
(1975) showed that montmorillonite had the highest adsorption capacity on pH level of 7.5(Al-Jlil and Alsewailem, 2009).Almost all of the adsorption process are affected by the pH of the solution (Mahmud,
2012). This happens because the pH of the solution and electrochemical properties affect thesurface charge of the particles or colloids. The changes of pH could affect the naturalcondition of sorption process, because ionization of organic compounds depends on pH levelof wastewater, which then implicate to the solubility of organic compounds in the solution(Maoz and Chefetz, 2010). However, the optimum pH is very specific to each compound, sothat solution with low pH is not always certain to produce a good adsorption process.
The influence of the dosage of clays to the adsorption of organic compounds
The experiment on the influence of adsorption clays dosages done on the pH optimumthat obtained from the results of previous experiments. Research done in batch for 120minutes with a dosages of clays of 2.5; 5; 10; 15; 20; 25; 30; and 35 gr/L. Analysis were donetowards the adsorption capacity of clays and COD removal efficiency. Results of theexperiment are shown in Figure 2.
For the use of Arcamanik clays, dosages variation of clay of 2.5; 5; 10; 15; 20; 25; 30;and 35 gr/L generate COD removal efficiency of 29.11%; 33.82%; 35.3%; 37.7%; 38.59%,and 39.38%. Optimum results achieved on the use of clay as much as 15 mg/L. While in theuse of Dago clay, adding dose of 2.5; 5; 10; 15; 20; 25; 30; and 35 gr/L generate CODremoval efficiency of 29.72%; 30.62%; 32.56%; 36.18%; 36.99%; and 37.74%.
0
10
20
30
40
50
3 4 5 6 7 8 9 10
Efficiency(%)
pH
Arcamanik
ClayDago Clay
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Figure 2. The Influence of Clays Dosages on The COD Removal Efficiency
The use of both clays gave similar result that the addition of dosages of clays were
proportional to the adsorption effeciency. The more clay were added, the higher organicremoval efficiency. This happened because the amount of adsorption sites were increase withthe higher adsorbent dosages, which resulting to the higher sorbate removal efficiency(Mumin, et al., 2007).
The influence of the contact time to the adsorption of organic compounds
In an adsorption process, process will continue to take place whenever the equilibriumstate has not reached. Therefore, to determine the equilibrium distribution betweenadsorbents with adsorbate, the experiments conducted with variations of the contact times.Determination of equilibrium state was done to predict when an absorber material reaches itssaturation level so that the process of adsorption had ended (Nilawati, 2013).
Figure 3. TheInfluence of Contact Time to The Adsorption Capacity and COD Removal.
On this experiment, analysis of adsorption conducted on optimal conditions that hadbeen acquired earlier (pH=7, field clay dose = 15 gr/L, and brown clay dose = 30 gr/L). Oneach of these conditions, analysis then conducted against contact time variations of 30, 60,90, 120, 150, and 180 minutes. The analysis result of the effect of contact time displayed onFigure 3.
25
27
29
31
33
35
37
39
41
0 5 10 15 20 25 30 35
CODRemovalEfficiency(%)
Dosages of Clay (gr/L)
Arcamanik Clay Dago Clay
0
10
20
30
40
50
60
0
2
4
6
8
10
12
30 60 90 120 150 180
Efficiency(%)
AdsorptionCapacity(mg/g)
Time (minutes)
Adsorption Cap: Arcamanik Cl Adsorption Cap: Dago Cl
Eff: Arcamanik Clay Eff: Dago Clay
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Figure 3shows that the longer the contact between the adsorbate with the adsorbents,the more adsorbate adsorbed. This can be seen from the increase in capacity in bothadsorption clays are used. For both types of clays, the optimum point where COD removalefficiency reaches its equilibrium point. The time to reach equilibrium state are different onevery adsorption process, it is influenced by the interaction types happen between adsorbent
and adsorbate (Wicaksono, 2012). On the use of Arcamanik clay, the equilibrium pointreached at the 120th minutes, as well as the use of Dago clay.
For the use of Arcamanik clay, the efficiency of COD removal in 30, 60, 90, 120, 150and 180 minutes are: 35.23%, 37.14%, 42.85%, 48.57%, 48.57%, and 48.57%. Theadsorption capacity of clays towards the variation of contact times respectively are: 8.27;8.72; 10.06; 11.4; 11.4; and 11.4 mg/g. As for the use of Dago clay, removal efficiency ofCOD at 30, 60, 90, 120, 150 and 180 minutes are: 24.13%; 24.96%; 27.14%; 27.9%; 28.58%;and 29.11%, and the adsorption capacity are: 5.67; 5.86; 6.37; 6.55; 6.71; and 6.84 mg/g. Theequilibrium state for the use of both types of clays were estimated happened on 120thminutes.
Determination of adsorption isotherm modelDetermination of adsorption of organic compounds isotherm model are conducted inoptimum condition for each clay. Analysis of Langmuir follow an isotherm equation onequation 1. From a linear curve that plots relationship between the C/m versus C, it can bedetermined the value of the slope of the Qm(slope) and KLfrom the intercept of the curve.The result of Langmuir isotherm model for each of the clays are shown in Figure 4.
(a) Arcamanik Clay (b) Dago ClayFigure 4. Langmuir Isotherm
(a) Arcamanik Clay (b) Dago ClayFigure 5. Freundlich Isotherm
The Freundlich equation is an empirical equation employed to describe heterogeneoussystems, in which it is characterized by the heterogeneity factor 1/n. (Wicaksono and Effendi,
y = -18,62x + 0,241
R = 0,986
0,08
0,09
0,1
0,11
0,12
0,13
0,006 0,007 0,008
1/q
1/Ct
y = -76,77x + 0,606
R = 0,996
0,12
0,13
0,14
0,15
0,16
0,17
0,18
0,19
0,2
0,0054 0,0056 0,0058 0,006 0,0062
1/q
1/Ct
y = -1,364x + 3,898
R = 0,996
0,9
0,95
1
1,05
1,1
2,05 2,1 2,15 2,2
Logq
Log Ct
y = -2,768x + 6,986
R = 0,999
0,74
0,76
0,78
0,8
0,82
0,84
0,86
2,21 2,22 2,23 2,24 2,25 2,26
Logq
Log Ct
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2012). Freundlich isotherm e
results can be seen in Figu
isotherm model can be seen i
Table 5. Adsorption Par
IClays KL
(L/m
Arcamanik -0.012
Dago -0.007
In describing the mec
Freundlich isotherm model w
It is visible from the coeffic
close to the value 1 rather tha
isotherm showed that experi
using field and brown clays dThe value of 1/n that is
saturated adsorbate when des
because the price of 1/n is re
and the distribution of energy
SEM and FTIR resultsSEM (Scanning Electr
20,000 times. The SEM resul
shown on Figure 6, while Da
The morphological cha
to the organic compounds thboth clays shows that agglo
pores of clays that were initi
the surface of adsorbents occ
sorbate.
(a)Before Adso
Figure 6. Morphology
8
uation is obtained by plotting value of log
e 5. While the values of KF, 1/n and R2
Table 5.
meters obtained From Langmuir and Freun
soterm Langmuir Isoterm Fr
)
Qm
(mg/g)
R KF
(mg/g)/(mg/L)1/n
94 4.149 0.986 7.9x103
89 1.65 0.996 9.68x106
anisms of adsorption of COD using field
as able to describe it better than the Langm
ent of determination (R2) Freundlich isoth
n Langmuir isotherm. A negative value for t
ental data are obtained on the process of
es not have compatibility with Langmuir iso less than one indicates that the adsorbent
ending on the adsorption energy density of
lated to the magnitude of the forces (drivin
sites on adsorbents (Karanfil, et al., 1999 in
n Microscopy) analysis were done with th
of the Arcamanik clays before and after ads
o clays shown on Figure 7.
ges of clays before and after adsorption pr
at filled the pores of the adsorbents. The fieration on the surface of particles has ha
lly empty, became filled by organic compo
red because of physical and chemical bonds
rption (b)After A
of Arcamanik Clays by SEM with 20,000
q and log Ce. The
f each Freundlich
lich Isotherm.
undlich1/n R
-1.364 0.996
-2.768 0.999
and brown clays,
ir isotherm model.
rm model is more
e KLon Langmuir
dsorption of COD
therm model.as molecules with
the surface. This is
g force) adsorption
ahmud, 2012).
e magnification of
orption process are
cess happened due
nal morphology ofpened, so that the
nds. The filling of
between clays and
sorption
agnification
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(a)Before Adsorption (b)After Adsorption
Figure 7. Morphology of Dago Clays by SEM with 20,000 Magnification
FTIR (Fourier Transform Infrared Spectroscopy) analysis was conducted to identify
materials and the presence of functional groups in clays. The FTIR result for Arcamanikclays, before and after adsorption process are shown on Figure 8.a and 8.b.Vibration on wavenumbers 2923.56 cm-1; 1346.07 cm-1; 1411.64 cm-1shown on Figure
8.a gives information about the presence of C-H bonds (Skoog, et al., 1984). Stretchvibration on 3189.68 cm-1and bendon 1558,2 cm-1happened because of the presence of N-H
bond (Silverstein, 1998). The double bond of C=C and O-H bond were detected by thevibration on 1643.05 cm-1 and 3625.52 cm-1, while stretch vibration on 2553.29 cm-1wavenumber shows the presence of S-H bond (Coates, 2000).
Figure 8.aInfrared Spectrum of Arcamanik Clay before Adsorption Process
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Figure 8.bInfrared Spectrum of Arcamanik Clay after Adsorption Process
FTIR result of Dago clay, before and after adsorption process shown on Figure 9.a and9.b. Vibration on wavenumbers 2854.13 cm-1; 2923.56 cm-1; and 2688.28 cm-1 shows the
presence of O-H stretch bond. The presence of C=O amides and N-H amines shown by thevibration on 1639.2 cm-1. Vibration on 782,95 cm-1wavelength indicates the S-O bond withthe sulfonate functional groups (Glagovich, 2013).
Figure 9.aInfrared Spectrum of Dago Clay before Adsorption Process
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Figure 9.bInfrared Spectrum of Dago Clay after Adsorption Process
According to Wan Ngah, et al(2008), if not much changes in wavenumbers happensafter the adsorption process, or no appearance on new waves peak, then the adsorptionmechanism happened phisicaly (Mahmud, 2012). Comparison between the existence of thewave peaks at the beginning and end of the adsorption on the use of Arcamanik clay ( Figure8.a and 8.b), shows that there are similarities between the two forms. However, there are new
peaks after the adsorption process. The same phenomena shown with the use of Dago clay.The emergence of these new peaks showed bonds between the adsorbate and the
functional groups of adsorbent (Wan Ngah and Hanafiah, 2008 in Mahmud, 2012). The peakintensity of the Arcamanik clay after adsorption showed little displacement and substantiallylower than that before adsorption process. This happens due to the involvement of functionalgroups of adsorbent in the bond between adsorbate and adsorbent (Wan Ngah and Hanafiah,2008 in Mahmud, 2012).
The result of FTIR analysis obtained correspond to the isotherm adsorption modelresult in this experiment. The isotherm model that more accurately described the adsorption
process of organic compounds using both clays is the Freundlich isotherm. The suitabilitywith Freundlich isotherm gave information that the adsorption process was dominated by
physical mechanisms (Sahan, et al., 2012).The influence of clays addition as coagulant aid to the COD removal
The experiment was done by first determining the optimum coagulant dose (alum)through jar test experiment. Coagulant dose variation that is added is equal to 10, 20, 30, 40,50, and 60 mg/L of alum. Figure 10shows the jar test results of the optimum dosage of alum.
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Figure 10. Turbidity Removal Efficiency on Dosages Variation of Alum
Figure 10 shows that the addition of alum with variation of dosages from 10 to 100mg/L generate the removal efficiency of turbidity respectively 21%; 31.57%; 32.72%;
36.62%; 35%; 30.42%; 27.92%; 24.53%; 25.82%; and 28.38%. Based on this result, theoptimum dosage of alum is 40 mg/L, that is with the highest removal efficiency of 36.62%.Since the hypothesis of this research is that the addition of clay are able reduce the need
for chemical coagulant (alum), then next experiment was carried out with the use of alumdose of 1 level below its optimum dose. Alum dosage that used taken as the maximum doseof clay addition, with variations of 15, 20, and 30 mg/L of clays dosages. Figure 11 showsthe coagulation-flocculation result with the addition of clay coagulant aid.
With the initial COD concentration of 364.26 mg/L, the addition of Arcamanik claywith dosages 15, 20, and 30 mg/L generate the final COD concentration of 357.4; 323.02;and 316.15 mg/L. The COD removal efficiency are 1.88%; 11.32%, and 13.2%. While for theuse of Dago clay, the final COD concentration are 350.51; 329.89; and 302.4 mg/L, with the
removal efficiency of 3.77%; 9.43%; and 16.98%.
Figure 11. COD Removal Efficiency in Coagulation Process towards Dosages Variations ofClays
Based on that result, it can be concluded that the addition of more clays able to producehigher COD removal efficiency, for the use of both clays. This happened because clays areable to act as adsorbent of organic compounds, so that the organic removal efficiency of
wastewater are proportional to the dosages of clays added.
0
5
1015
20
25
30
35
40
0 20 40 60 80 100 120
Remova
lEfficiency(%)
Dosages of Alum (mg/L)
0
2
4
6
8
10
12
14
16
18
270
280
290
300
310
320
330
340
350
360
15 20 30
RemovalEfficiency(%)
COD(mg/L)
Dosages of Clay (mg/L)
[COD] Arcamanik Cl
[COD] Dago Cl
Eff: Arcamanik Cl
Eff: Dago Cl
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The next stage of research is to compare the COD removal efficiency in coagulationprocess, with and without the addition of clays coagulant aid. In this experiment, dosages ofchemical coagulant that are use as comparison on coagulation-adsorption process are theoptimum coagulant dose and one level below the optimum dose (30 and 40 mg/L). Theexperiment result shown on Figure 12.
Figure 12.The Influence of Addition of Clays on Alum Coagulation
The initial concentration of COD contained in the wastewater was 409.78 mg/L. TheCOD removal efficiency of processes: with addition of Arcamanik clay, Dago clay, alumonly with the dose of 30 mg/L, and alum only with 40 mg/L of dose are: 13.43%; 11.94%;8.95%; and 17.9%.
This result shows that the addition of clays were able to improve the COD removalefficiency in coagulation process. This happened because the combination of coagulation-adsorption were able to cover each other deficiencies. Organic compounds that were removed
by the process of coagulation were compounds with high molecular weight and have anegative charge. While the use of activated carbon more effectively to adsorp compoundswith small molecular weights and are uncharged (Shen and Chaung, 1998). However, theresult was still lower than COD removal efficiency with the use of alum on its optimum dose(40 mg/L), that was 17.9%.
CONCLUSIONBoth type of clays that used have the ability as adsorbent towards organic compounds
in wastewater. The optimum condition on the use of Arcamanik and Dago clays are at pH 7and clays dosages of 15 and 30 mg/L. COD removal reached equilibrium point on the 120th
minutes of the contact time, for the use of both Arcamanik and Dago clays.Isotherm model that more accurately described the adsorption process in this researchwas Freundlich isotherm model. The suitability with Freundlich isotherm gave informationthat the adsorption process was dominated by physical mechanisms
In general, the coagulation process with the addition of clay coagulant aid was able toincrease the removal of pollutant parameters in textile wastewater. However, this researchwas not able to prove the hypothesis that the addition of clay coagulant aid was able todecrease the need for chemical coagulant.
0
5
10
15
20
25
CODRemovalEfficiency(%)
Arcamanik Clay Dago Clay Alum 30 mg/L Alum 40 mg/L
8/10/2019 2013 Andita Rachmania SIBE
14/14
14
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