Research Article Adsorption of Polyvinylpyrrolidone over the Silica Surface…downloads.hindawi.com/journals/ijps/2016/2417292.pdf · 2019-07-30 · Research Article Adsorption of

Research ArticleAdsorption of Polyvinylpyrrolidone over the SilicaSurface As Affected by Pretreatment of Adsorbent andMolar Mass of Polymer Adsorbate

Laila M Al-Harbi1 Samia A Kosa1 Musa K Baloch23 Qaisar A Bhatti2

and El-Sayed El-Badawey H El-Mossalamy4

1Department of Chemistry Faculty of Science King Abdulaziz University PO Box 80203 Jeddah 21589 Saudi Arabia2Institute of Chemical Sciences Gomal University Dera Ismail Khan 29050 Pakistan3Department of Chemistry University of Sargodha Subcampus Bhakkar Bhakkar 30000 Pakistan4Department of Chemistry Faculty of Science Benha University Benha 13518 Egypt

Correspondence should be addressed to Laila M Al-Harbi lalhrbikauedusa

Received 31 October 2015 Revised 8 April 2016 Accepted 13 April 2016

Academic Editor Angel Concheiro

Copyright copy 2016 Laila M Al-Harbi et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The adsorption of polyvinylpyrrolidone over the surface of silica has been investigated The impact of molar mass of the polymerpH and pretreatment temperature of silica particles have been evaluated by means of FTIR spectroscopy and electrophoreticmeasurements The silica particles used have narrow particle size distribution The zeta potential of the aqueous silica suspensionwas decreased with the increase in pH The amount of polymer adsorbed was increased with the increase in pretreatmenttemperature time concentration pH zeta potential and molar mass of the polymer The addition of polymer to the systemincreased the zeta potential due to adsorption of polymer on the surface of the particles However the impact increased withthe increase in molecular mass of the polymer The IR spectra obtained before and after adsorption of polymer concluded thatmostly hydrogen bonding is responsible for the adsorption phenomena however hydrophobic interactions also play a significantrole The mechanism has been investigated and established through FTIR spectroscopy

1 Introduction

Dispersion in both aqueous and nonaqueous media isused in numerous products including paints dyestuffs pig-ments printing inks papers adhesives cosmetics deter-gents ceramics and pharmaceutical and pesticide formu-lations Use of coagulants to clarify drinking water waspracticed in ancient time in China and in Egypt Mineral andenvironmental engineers have applied the concepts of colloidscience to help them utilize and preserve enormous resourceswhich otherwise were waste material [1] Nowadays ceramicproducts ranging from building bricks to expensive china torocket parts are made from clay-water sols by applying prin-ciples of colloid science [2] The wide use of colloid sciencein the areas of cosmetics and detergents has added many

products to our daily life [3] Knowledge of human life eitherwritten on paper or stored on film or disk has dependedupon the application of colloidal science in papermaking anddevelopment of new magnetic and electronic materials andso forth [4]The dispersion activity of suchmaterial is mostlycontrolled through the addition of polymer or a mixture ofpolymers and surfactants and the interactions of surfactantsandor neutral water polymers in aqueous solutions withsolid particles play a vital role in such applicationsThereforethe investigation of these interactions has been an activefield of interest [5ndash9] On the other hand the interaction ofpolymers with solidliquid interface has not attained somuchattention despite the importance of polymer adsorption overthe solidliquid interface [10ndash15] Further the degree andnature of adsorption of polymer depend on the suspended

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2016 Article ID 2417292 9 pageshttpdxdoiorg10115520162417292

2 International Journal of Polymer Science

Table 1 Physicochemical properties of AEROSIL OX 50 as per the manufacturer information

Source BET surface area PZC at pH SiO2Contents pH Primary particle size Tapped approximate densityEvonik Industries 50 + 15 (m2 gminus1) 32 ge998 38ndash48 04 (120583m) 130 (gL)ldquoPZC at pHrdquo signifies the PZC (point of zero charge) at pH at which surface charge of the particle is zero

particles and hence affect the stability of the dispersion[16] In addition to that the surface charge-to-mass ratioof the particle plays a very important role in stabilizingthe dispersion and this parameter is very much dependentupon the pH of the solution size of particles and so forthAlthough a number of research papers have been publishedto understand themechanism of adsorption of polymers overthe solid surfaces unfortunately none of the papers dealswith the prediction of adsorption behavior of a polymer overthe solid surface up to the required level [17 18]

Polyvinylpyrrolidone also named Povidone or PVP isa nonionic amphiphilic polymer Because of its exceptionalcombination of properties like low toxicity biocompatibilityfilm forming and adhesive characteristics complexing abilityto proton donors and low osmotic pressure it finds diverseapplications in various fields of life like pharmaceutical andcosmetic products food adhesives and textile auxiliaries ascompared to other water-soluble polymers like polyethyleneoxide and polyvinyl alcohol [19ndash21] In spite of these factsmechanisms involved in such processes are not well under-stood and hence need detailed and systematic exploration forproper utilization of silica [6 12ndash14 22] AEROSIL OX 50because of its physicochemical properties has a large numberof applications Among fumed silica AEROSIL OX 50 dueto its specific properties is widely used in biotechnologyagriculture medicine and pharmaceutics

Since surface modification of an oxide via polymeradsorption leads to a change in its physicochemical character-istics therefore the main objective of this work was to inves-tigate in detail the adsorption behavior of PVP onto silicain its aqueous suspension by using UV FTIR spectroscopyelectrophoresis and measurement techniques and to explorethe impact of particle size of silica temperature pretreatmentof adsorbent molecular mass of polymer and so forth on theadsorption phenomenon and to make use of that data for theexploration of the mechanism

2 Experimental

21 Materials AEROSIL OX 50 fumed silica oxide obtainedfrom Degussa Evonik Industries Germany was used as amodel substrate Some of the characteristics of AEROSILOX 50 are presented in Table 1 These properties were alsoverified by employing a mercury porosity meter (Autosorb-1der FirmaQuanta chrome USA) pH and LDmeasurementsand scanning electron microscopy The specific surface areareported by the manufacturer was 50 plusmn 15 (m2sdotgminus1) but whenmeasured it was 4072 (m2sdotgminus1)

Three different samples of PVP also known as Luvitecwere obtained from BASF Germany PVP had three differentmolar masses and was used as a stabilizer for the silicadispersion Some of the basic properties of PVP as provided

Table 2 Some of the basic properties of PVP as provided by themanufacturer BASF Germany

Sample PVP K17 PVP K30 PVP K90MwK dalton 7ndash11 45ndash55 1200ndash2000Degree of dispersity 18 plusmn 02 23 plusmn 02 34 plusmn 03Rel viscosity 1 in water 1075ndash1110 1201ndash1291 3991ndash6197

by the manufacturer are listed in Table 2 Water used for thedispersion was obtained fromMillipore GmbH SchwalbachGermany having pH around 65 and conductance of 25 120583S

22 Methods

221 Characterization of Silica Theparticle size and size dis-tribution of silica were determined using scanning electronmicroscope (Jowl Japan) and laser diffraction particle sizeanalyzer Mastersizer 2000 Malvern Co UK equipped withimpeller mixture The surface area of the material was esti-mated using mercury porosity meter (Autosorb-1 der FirmaQuanta chrome USA) Surface charge was measured usingZetasizer 3000 (Malvern Co Germany) The surface chargedensity 119902 in relation to pH was measured by polyelectrolytetitration using Particle ChargeDetector (PCDMutekGmbHGermany) FTIR Tensor Bruker Germany was used for IRspectra measurement

222 Pretreatment of Silica For this purpose the adsorbent(silica) was heated at five different temperatures from 298Kto 523K for three hours in a vacuum oven (Gallon KampUK) under inert atmosphere and then cooled to roomtemperature in a desiccant The sample so obtained was usedfor adsorption studies [23]

223 Characterization of Polymer The polymer was char-acterized by laser light scattering technique the instrumentused for the purpose was DAWN EOS supplied by WyattUSA with helium-neon laser of 6328 nmwavelength as lightsource

224 Adsorption Studies Polymer solution was preparedin water having concentration 0ndash80 ppm The solution wasmixed with 005 g of preheated adsorbent20mL of polymersolution in 100mL sample bottles for 3 hours at differenttemperatures The samples were equilibrated for 16 hours at298K at 85 rpm using orbital shaker (Sanyo Orbit Japan)Thereafter the supernatant was removed from samples bycentrifuging at 21000timesg for 15 minutes using centrifugemodel OSK12710 (Gawasieki Co Japan) and analyzed forpolymer concentration

International Journal of Polymer Science 3

AEROSIL OX 50

Wavenumber (cmminus1)

500 1000 1500 2000 2500 3000 3500 4000

00

02

04

06

08

10

Tran

smitt

ance

()

Figure 1 FTIR spectra of silica

The pH dependent adsorption experiments were per-formed at pH 2ndash10 at 298K The pH of the solution wasmaintained using HNO

3and KOH pH of the solution was

measured using pH meter supplied by Denwer USA

225 Analytical Measurements The amount of unabsorbedPVP in the supernatant was determined using spectroscopictechniques For this purpose the UV-visible spectropho-tometer employed was Lambda 800 (PerkinElmer) and 120582maxused for measurement was 196 nm

226 Zeta Potential Measurement The zeta potential ofparticles was measured using Zetasizer 3000 supplied byMalvern Germany 120577

0and 120577 of silica were measured before

and after the adsorption process The contents of silicaused during the electrophoretic measurements were 01 gLminus1KCl was used as an electrolyte of (1 times 10minus3molL) knownconcentration Electrophoretic mobility of the samples wasmeasured after allowing sufficient conditioning time to attainequilibrium at the required pH [24ndash26]

227 FTIR Spectroscopic Studies FTIR spectra of silica PVPand PVP adsorbed over silica were recorded over the rangeof 4000 cmminus1 to 400 cmminus1 wavenumber by using KBr pellet(Figure 13) The instrument used for the purpose was FTIRTensor Bruker Germany

3 Results and Discussion

Fumed silica (AEROSIL OX 50) obtained from the supplierwas characterized with respect to its purity surface chargesize and surface area FTIR spectra of the samples aredisplayed in Figure 1

The literature reveals that FTIR spectra of pure silica typi-cally display peaks in two discrete regions withwavenumbersgreater than 2500 cmminus1 and less than 1300 cmminus1 [7 8] Theformer region corresponds to hydroxyl (minusOH) stretching dueto absorbed or molecular water However in our case we

minus60

minus40

minus20

0

20

Zeta

pot

entia

l (m

V)

2 3 4 5 6 7 8 9 101pH

Figure 2 Zeta potential of 1 aqueous dispersion AEROSIL OX 50measured in 1 times 10minus3MKCl The error percentage was about 50

did not observe any peak in this region It was attributedto heat treatment of the silica before adsorption The latterregion is observed due to different modes of silica [8] andthree prominent peaks were observed The peak at 460 cmminus1was assigned to rocking motion of oxygen atoms bridgingsilicon atoms in siloxane bonds (SindashOndashSi) A broader peakat 810 cmminus1 was assigned to OndashSindashO vibration mode of SiO

2

which was due to symmetric vibrations of silicon atoms ina siloxane bond [27] A peak at 1105 cmminus1 along with weakabsorption at 960 cmminus1 was the largest peak observed ina silica spectrum and was assigned to SindashOndashSi and SindashOstretching vibrationmodes of isolated SindashOH groups Similarbands were observed by Guzenko et al [9] The values werein good agreement with those reported in the literature [7ndash9 28 29] indicating that the material was pure and heatingwas performed properly

As the stability of dispersion also depends upon thecharge of the particle the surface potential of the particleswasdetermined as a function of pH which was adjusted using 1 times10minus3M KOH and 1 times 10minus3M HNO

3 The measurement was

made in 1 times 10minus3MKCl solution at 25∘C using Malvern ZetaMaster The results obtained are displayed as a function ofpH in Figure 2 which shows a negative zeta potential in thepH range from 32 to 10 The isoelectric point was about 32It indicated that the dispersion with pH near the isoelectricpoint (32) was unstable If the charge is high the particleswill remain separated and dispersed and the suspension willbe stable and vice versa According to the results the chargeandhence the stability should be the highest in basic pH rangebecause the zeta potential in this range is high

In aqueous suspensions of silica particles the surfacesilicon and oxygen bonds are unsatisfied and are neutralizedby OHminus and H+ species As a result partial or total particlesurface hydroxylation can result in the formation of silanolgroups [Si(OH)n] which dissociate in pure water through thefollowing reactions

SiOH +OHminus 997888rarr SindashOminus +H2O (1)

SiOH +H+ 997888rarr SindashOH+ +H2O (2)


Figure 3 SEM picture of AEROSIL OX 50

That is why silica particles may end negatively charged inwater suspension for basic pH and positively charged underacidic pH [30 31] These phenomena impact directly the zetapotential behavior of silica suspensions and cause a slightchange in zeta potential with a change in pH

The rest of the measurements were therefore performedat pH 6 at room temperature with a negative zeta potential ofabout minus47mV

The electron micrographs of AEROSIL OX 50 are dis-played in Figure 3 The micrographs showed that althoughthe particles are monodispersed they are aggregated whichmay affect their adsorption and dispersion and stabiliza-tion properties Although ultrasonication was performed for30min it was impossible to break the aggregates completelyas concluded by the manufacturer

The results obtained from Mastersizer after homogeniz-ing the system with magnetic stirrer for one hour and ultra-sonication for various time periods are shown in Figure 4

The figure indicates monodispersity in the size of theparticles however some aggregates are visible in the imagesThe particle sizes obtained in the aqueous dispersed phase forthe samples sonicated for different times ranged from 220 to900 nmwith an average of 400 nm as is displayed in Figure 4These plots also show monodispersity to some extent whilethe polydispersity is attributed to aggregates that are presentin the system Furthermore these observations are in accordwith information provided by the manufacturer

The figure also indicated that the sonication time has analmost negligible impact on the size and size distributionHowever the degree of dispersity was first decreased and thenwas increased if the sonication time was longer than 20minThis trend was attributed to the balance between shear andcolloidal forces This phenomenon is further supported by

120574119888= 119891(119904120590

120578119860119886) (3)

Here 120574119888is the critical shear rate 119904 is the ratio of particle

to medium viscosity 120590 is interfacial tension 120578119860is droplet

viscosity and 119886 is the size of the particleEquation (3) states that aggregate formation or disinte-

gration depends upon the critical shear rate It is important

1hr homogenization5min ultrasonication10min ultrasonication

20min ultrasonication30min ultrasonication

02 04 06 08 1000

Particle size (120583m)

0

5

10

15

20

25

30

35

Volu

me (

)

Figure 4 Particle size distribution of AEROSIL OX 50 (1 aqueousdispersion) measured after sonification for various duration usingMastersizer The error percentage was about 35


500 1000 1500 2000 2500 3000 3500 4000 4500

00

02

04

06

08

10 PVP

Tran

smitt

ance

()

Figure 5 FTIR spectra of polyvinylpyrrolidone

to note that the critical shear rate is inversely proportional tothe size of the particles [32] This means that if the size of theparticles is small then the high shear rate is needed to furtherdecrease the size

The FTIR spectra of the polymer (PVP) used showeda good agreement with the literature indicating that thepolymer was pure (Figure 5) [10 29]

The results obtained for molecular weight and degree ofdispersity of polymerwere 918 (18) 4996 (23) and 143times 103(34) Kgmol It was noted that with the increase inmolecularmass of the polymer the degree of dispersity was increasedand the results were the same (within experimental error) assupplied by the manufacturer shown in Table 2


000

002

004

006

008

010

Am

ount

adso

rbed

(mg

mminus2)

5 10 15 20 250Adsorption time (hr)

Figure 6 Adsorbed amount of PVP as a function of timeThe errorpercentage was about 25

Time dependent adsorption curves are frequentlyobserved in polymer adsorption [29] It is sometimesassumed that reconfirmation processes play an importantrole in determining the rate of adsorption However forpolydisperse polymers this is not the only possibilitysince small chains on the surface may be replaced by thebigger ones leading to a slow increase in adsorbed amountAlthough the time scale of such processes in not known itis expected that they contribute significantly to the overalltime dependent adsorption Therefore the amount of K90adsorbed was measured after 24 hours of mixing The silicaconcentration was 05 gdmminus3 and the starting concentrationof the PVP was 80 ppm It can be seen that the adsorbedamount was increased sharply during the first 10 hours andthen leveled off (Figure 6) On the bases of these observationsand for practical reasons we chose 16 hours as adsorptiontime in all adsorption experiments

Adsorption isotherms for the polymer of different molec-ular masses are shown in Figure 7 It was noted that theisotherms were of Langmuir type and of high affinity and thatthe amount adsorbed was increased from 04 to 08mgmminus2with the increase in molecular mass of the polymer [33 34]It was noted from the isotherms that initially the adsorptionwas increased very rapidly with the increase in concentrationof polymer and ultimately it leveled off This was accreditedto the fact that initially the availability of the surface free siteswas high and hence adsorption took place faster Howeveras the time passed the equilibrium was established andavailability of free sites was reduced to almost zero andhence the adsorption became difficult and rate of adsorptionbecame almost zero The maximum amount of polymeradsorbed onto the surface of silica was increased with theconcentration of polymer These findings were in line withthe expectations [35 36]

The amount of polymer (PVP) adsorbed per unit surfacearea was calculated using Langmuir adsorption The datagave exactly straight lines and the average value obtained in

00

02

04

06

08

10

Am

ount

adso

rbed

(mg

mminus2)

10 20

PVP K90 PVP K17PVP K30

30 40 50 600Equilibrium concentration (ppm)

Figure 7 Adsorption isotherms of PVP having different molecularmass on AEROSIL OX 50 measured at 298K The error percentagewas about 25

this way was 06mgsdotmminus2 (Figure 7) However this value wasslightly less than (10mgsdotmminus2) the adsorbed concentration fora calculated condensed monolayer of monomer units

Although the adsorbed amount was increased muchwith increasing the molar mass of the polymer for highermolecular mass leveling off of adsorption took place Themaximum amount adsorbed at plateau region was consis-tent with the data published in the literature [37 38] Theadsorption capacity was found to be a function of molecularmass showing similar dependency to that reported by CohenStuart et al [39] Polymer-solvent interaction and segmentaladsorption energy parameter are the two main factors whichmay work behind this phenomenon Low polymer-solventinteraction is a poor solvent and high segmental adsorptionenergy parameter That is strong attachment of the segmentsmay lead to a high adsorbed amount of polymer [39]

The amount adsorbed at plateau coverage was plottedas a function of log119872119908 in Figure 8 It was observed thatthe increase in adsorption was very sharp for low molecularmass and ultimately leveled off for highmolecularmass Sincewe have used polymer with only three molecular massesand worked with lower concentrations therefore for a betterunderstanding of this trend data reported by Cohen Stuart etal and Robinson and Williams [34 38 40] were also plottedin Figure 8 for comparison purpose and the results showed anexcellent agreement It is interesting to note that although theamount adsorbed was increased with the molecular weightand then leveled off the values inmMm2 were decreased andfollowed a single exponential relationship irrespective of datasource (Figure 8) This type of behavior could be explainedin terms of variation in conformation of polymer chains withthe molecular mass

In order to find out the effect of pH over the adsorptionof polymer wemeasured the adsorbed amount at various pH


Cohen Stuart et alRobinson and Williams

Present

y = 00752eminus1881x

00000001

0000001

000001

00001

0001

Am

ount

adso

rbed

(mM

m2)

4 5 6 73log(molecular mass)

Figure 8 The amount of polymer adsorbed as a function of molec-ular mass of polymer

AdsorptionZeta potential

075

08

085

09

Am

ount

adso

rbed

(mg

m2)

minus60

minus40

minus20

0

20Ze

ta p

oten

tial

3 5 7 9 111pH

Figure 9 Amount of polymer adsorbed over silica as a function ofpHThe error percentage was about 25 in adsorption and in case ofzeta potential it was 5

The results obtained are plotted in Figure 9 The results con-cluded that the adsorbed amount is the highest at low pH andwas decreased with the increase in pH and ultimately levelsoffThe same trend was observed for all the polymer samplesindicating that the pH had the same impact irrespective ofmolecular mass To explore the cause of such trend the zetapotential and amount adsorbed have been plotted against pHin the same figureThe figure concludes that the adsorption isverymuch related to surface charge of the solidmaterial usedFurther to it the solvent quality will deteriorate for polymerwith the increase in pH and hence conformation of polymerwill change which may result in a decrease in adsorption ofpolymer

Since it is observed that heating causes a reduction in thesilanol-group density on the surface of silica particles [41 42]it is important to have some knowledge about the importanceof these groups in the phenomenon of polymer adsorption

PVP K17PVP K30

PVP K90

04

05

06

07

08

09

Am

ount

adso

rbed

(mgmiddot

mminus2)

350 400 450 500 550300Temperature (K)

Figure 10 Effect of pretreatment of AEROSIL OX 50 on theadsorption of PVP The error percentage was about 25

Therefore a study of the impact of preheating silica on theadsorption of PVP has been conducted The adsorbent washeated for three hours from 298K to 523K at five differenttemperatures and used for adsorption purpose The resultsobtained are plotted in Figure 10 The figure shows thatpreheating does not have a very pronounced impact on theadsorption for a specific temperature range By increasing thepretreatment temperature the amount of polymer adsorbedwas increased sharply Since we have worked over a range of298K to 523K to get detailed information in this regard weinterpolated our data with that of Alagha et al and Behrenset al [43 44] It is observed that a very little impact is seen upto 523K and at higher temperature of about 1273K a sharpincrease in amount adsorbed was observed (Figure 11)

The initial smaller increase in amount adsorbed isattributed to the fact that desorption of gases andor waterduring heating of silica resulted in an increase in availabilityof free surface site for the adsorption and at the same timethe decrease in surface area limits the amount adsorbed [43ndash45]Therefore no significant amount adsorbedwas observedHowever at higher temperature a sharp increase revealedthe fact that at higher temperature a significant reduction ofsurface area takes place along with the removal of surfacesilanol groups which made the silica more hydrophobic andan increase in the amount adsorbed is due to this hydrophobicinteraction between polymer and the silica surface Ourfindings are in very good agreement with those reported inthe literature [44 45]

The impact of preheating of silica on the adsorptionof PVP was investigated by heating the samples at fivedifferent temperatures from 298K to 523K and the resultsobtained are plotted in Figure 11 The figure showed that


400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17

Figure 11 Effect of pretreatment of AEROSIL OX 50 on adsorptionof PVP The reported data are our own and the one reported byCohen Stuart et al [39]

by increasing the pretreatment temperature the amount ofpolymer adsorbed was increased significantly An increasein the amount adsorbed for low temperature was attributedto desorption of gases andor water during heating of silicawhich resulted in an increase in availability of free surfacesite for the adsorption and at the same time the decrease insurface area limited the amount adsorbed [41 42] Thereforeno significant amount was adsorbed However at high tem-perature a significant increase in adsorption revealed that athigher temperature the removal of surface silanol groups tookplace [42 43] which made the silica more hydrophobic andan increase in the amount adsorbed took place However asignificant reduction of surface area also took place and thatreduced the adsorption up to a considerable amount Ourfindings are in very good agreement with those reported inthe literature [44 45]

Zeta potential ofAEROSILOX50 after adsorption of PVPwas obtained at pH 57 and 25∘C The results are displayedin Figure 11 as a function of PVP adsorbed amount Itwas observed that the zeta potential of AEROSIL OX 50was initially minus425mV and was significantly increased withthe increase in concentration of PVP due to adsorption ofpolymer over AEROSIL OX 50 As NndashC=O group is presentin PVP and is electron donor in nature it causes an increasein the surface charge on silica or enhances the shielding effectof the oxide surfaces [46] and hence was dependent uponconcentration and molecular mass of PVP This is the reasonwhy the pH of the media was increased by the addition ofthe polymer The figure also displayed that the charge overAEROSILOX50was increasedwith the increase inmolecularmass of PVP adsorbed It was attributed to the shift of theshare plan in case of adsorption of nonionic polymers [47]and the increase in number of monomers (active groups) ina chain of polymers

80

PVP K17PVP K30

PVP K90

20 40 600Concentration (ppm)

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)

Figure 12 Effect of PVP concentration andmolecularmass over thezeta potential of silica The error percentage was about 50

H

N

Hn n

Resonance in Polyvinylpyrrolidone

+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙

Scheme 1 Schematic presentation of resonating structure of poly-vinylpyrrolidone

To establish the mechanism of PVP adsorption ontoAEROSIL OX 50 FTIR spectroscopic measurements of thesamples were carried out before and after the adsorption ofPVP The spectra so recorded for AEROSIL OX 50 PVPand PVP adsorbed over AEROSIL OX 50 are displayed inFigure 12 for comparison purpose CH

2ndash band deformation

near 1460 cmminus1 in hydrocarbons and the splitting of the bandinto 1422 1460 and 1493 cmminus1 indicated the interchain forcesin PVP and strain in the five-membered rings Stretchingof CH

2(CH) NCO in PVP was indicated by pronounced

absorbance at 1287ndash1373 cmminus1 The absorbance shown bycarbonyl group in PVP at 1661 cmminus1 was in the range reportedearlier [47 48] The presence of C=O at 1661 cmminus1 wassignificant whereas the appearance of CndashO was very weakandmay be due to the canonical forms of PVP as representedby the structure (Scheme 1)

Strong evidence which supported the presence of hydro-gen bonding in adsorption of PVP on silica was that beforeadsorption of PVP the presence of C=O at 1661 cmminus1 wassignificant whereas the appearance of CndashO was very weakhowever after the adsorption process the C=O group almostdisappeared Therefore it was suggested that partial negativecharged oxygen of the C=O group caused the hydrogenbonding with the hydrogen of silanol This was furthersupported by the fact that PVP has NndashC=O groups which are


N

H

H

n

Polyvinylpyrrolidone Silica Interaction between PVP and Silica

+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus

Scheme 2 Schematic presentation of the adsorption of PVP on silica

Tran

smitt

ance

()

AEROSIL OX 50

PVP

AEROSIL OX 50 after adsorption


500 1000 1500 2000 2500 3000 3500 4000

Figure 13 FTIR spectra of silica PVP and silica after adsorption ofPVP

electron donor in nature [49] therefore hydrogen bondingbetween oxygen of C=O and hydrogen of silanols may havepossibly taken place Furthermore there is no evidencefor the conversion of CndashN into C=N as shown by theshifting of peaks from 1661 cmminus1 to 1078 cmminus1 [50] Schematicpresentation of the mechanism of PVP adsorption on silica isgiven by Scheme 2

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

This work was funded by the Deanship of Scientific Research(DSR) King Abdulaziz University Jeddah under Grant no130-128-D1434 The authors therefore acknowledge withthanks the DSR for technical and financial support

References

[1] P Somasundaran Y H C Wang and S Acar Future Trends inPolymer Science and Technology Technomic Publishing BerlinGermany 1987

[2] A G Evans and T G Langdon ldquoStructural materialrdquo Progressin Materials Science vol 21 p 174 1976

[3] H M Remz ldquoCosmetrdquo Toiletries vol 103 p 70 1988[4] V Novotny ldquoApplications of nonaqueous colloidsrdquo Colloids and

Surfaces vol 24 no 4 pp 361ndash375 1987[5] B K GTheng ldquoInteractions of clayminerals with organic poly-

mers Some practical applicationsrdquoClays andClayMinerals vol18 no 6 pp 357ndash362 1970

[6] C Ma and C Li ldquoInteraction between polyvinylpyrrolidoneand sodium dodecyl sulfate at solidliquid interfacerdquo Journal ofColloid and Interface Science vol 131 no 2 pp 485ndash492 1989

[7] G M Filippelli J W Carnahan D G E A Swann andS V Patwardhan ldquoApplication of Fourier Transform InfraredSpectroscopy (FTIR) for assessing biogenic silica sample purityin geochemical analyses and palaeoenvironmental researchrdquoClimate of the Past vol 7 no 1 pp 65ndash74 2011

[8] M Waseem S Mustafa A Naeem and K H Shah ldquoIrfan shahand ihsan-ul-haquerdquo Pakistan Material Society vol 3 no 12009

[9] N V Guzenko E M Pakhlov N A Lipkovskaya andE F Voronin ldquoSorption modification of fine silica withpolyvinylpyrrolidonerdquo Russian Journal of Applied Chemistryvol 74 no 12 pp 2017ndash2020 2001

[10] S Robinson and P A Williams ldquoInhibition of protein adsorp-tion onto silica by polyvinylpyrrolidonerdquo Langmuir vol 18 no23 pp 8743ndash8748 2002

[11] Th F Tadros ldquoThe interaction of cetyltrimethylammoniumbromide and sodium dodecylbenzene sulfonate with polyvinylalcohol adsorption of the polymermdashsurfactant complexes onsilicardquo Journal of Colloid and Interface Science vol 46 no 3 pp528ndash540 1974

[12] K Esumi and M Oyama ldquoSimultaneous adsorption ofpoly(vinylpyrrolidone) and cationic surfactant from theirmixed solutions on silicardquo Langmuir vol 9 no 8 pp 2020ndash2023 1993

[13] K Esumi and Y Yamanaka ldquoInteraction between sodium dode-cyl poly(oxyethylene) sulfate and alumina surface in aqueoussolutionrdquo Journal of Colloid and Interface Science vol 172 no 1pp 116ndash120 1995

[14] B M Moudgil S Behl and N S Kulkarni ldquoMeasurement ofheat of adsorption of polyethylene oxide on dolomite silica andalumina by microcalorimetryrdquo Journal of Colloid And InterfaceScience vol 148 no 2 pp 337ndash342 1992

[15] K Chari and W C Lenhart ldquoEffect of polyvinylpyrrolidone onthe self-assembly of model hydrocarbon amphiphilesrdquo Journalof Colloid and Interface Science vol 137 no 1 pp 204ndash216 1990

[16] A H Otsuka and K Esumi ldquoSimultaneous adsorption ofpoly(vinylpyrrolidone) and anionic hydrocarbonfluorocarbonsurfactant from their binary mixtures on aluminardquo Langmuirvol 10 no 1 pp 45ndash50 1994


[17] R Bury B Desmazieres and C Treiner ldquoInteractions betweenpoly(vinylpyrrolidone) and ionic surfactants at varioussolidwater interfaces a calorimetric investigationrdquo Colloidsand Surfaces A Physicochemical and Engineering Aspects vol127 no 1-3 pp 113ndash124 1997

[18] G D Parfitt ldquoThe role of the surface in the dispersion of pmdersin liquidsrdquo Pure and Applied Chemistry vol 53 pp 2233ndash22401991

[19] V E Killmann and H G Wiegand ldquoCharakterisierungadsorbierter makromolekulschichten durch ellipsometrierdquo DieMakromolekulare Chemie vol 132 no 1 pp 239ndash258 1970

[20] CW Francis ldquoAdsorption of polyvinylpyrrolidone on referenceclay mineralsrdquo Soil Science vol 115 no 1 pp 40ndash54 1973

[21] M A Cohen Stuart G J Fleer and B H Bijsterbosch ldquoTheadsorption of poly(vinyl pyrrolidone) onto silica I Adsorbedamountrdquo Journal of Colloid And Interface Science vol 90 no 2pp 310ndash320 1982

[22] A Fidalgo and L M Ilharco ldquoThe defect structure of sol-gel-derived silicapolytetrahydrofuran hybrid films by FTIRrdquoJournal of Non-Crystalline Solids vol 283 no 1ndash3 pp 144ndash1542001

[23] Q A Bhatti M K Baloch S Schwarz and G Petzold ldquoImpactof various parameters over the adsorption of polyvinylpyrroli-done onto kaolinrdquo Journal of Dispersion Science and Technologyvol 33 no 12 pp 1739ndash1745 2012

[24] J Kim and D F Lawler ldquoCharacteristics of zeta potentialdistribution in silica particlesrdquo Bulletin of the Korean ChemicalSociety vol 26 no 7 pp 1083ndash1089 2005

[25] J A A Junior and J Baptista Baldo ldquoThe behavior of zetapotential of silica suspensionsrdquo New Journal of Glass andCeramics vol 4 no 2 pp 29ndash37 2014

[26] Q A Bhatti M K Baloch S Schwarz andG Petzold ldquoEffect ofvarious parameters on the stability of silica dispersionsrdquo Journalof Solution Chemistry vol 43 no 11 pp 1916ndash1928 2014

[27] Z H Cheng A Yasukawa K Kandori and T Ishikawa ldquoFTIRstudy on incorporation of CO

2into calcium hydroxyapatiterdquo

Journal of the Chemical Society Faraday Transactions vol 94no 10 pp 1501ndash1505 1998

[28] E F Voronin L V Nosach N V Guzenko E M PakhlovandO L Gabchak ldquoAdsorptionmodification of nanosilica withnon-volatile organic compounds in fluidized staterdquo Nanoma-terials and Supramolecular Structures Physics Chemistry andApplications pp 169ndash177 2010

[29] R Levy and C W Francis ldquoInterlayer adsorption ofpolyvinylpyrrolidone on montmorilloniterdquo Journal of Colloidand Interface Science vol 50 no 3 pp 442ndash450 1975

[30] D Frenkel ldquoPlaying tricks with designer lsquoatomsrsquordquo Science vol296 no 5565 pp 65ndash66 2002

[31] P M Dove and J D Rimstidt ldquoSilica water interactionsmdashinsilica reviews in mineralogyrdquo Mineral Society of America vol29 pp 259ndash307 1994

[32] G I Taylor ldquoThe formation of emulsions in definable fields offlowrdquo Proceedings of the Royal Society A vol 146 no 858 pp501ndash523 1934

[33] A Silberberg ldquoThe adsorption of flexible macromolecules PartI The isolated macromolecule at a plane interfacerdquoThe Journalof Physical Chemistry vol 66 no 10 pp 1872ndash1883 1962

[34] J M H M Scheutjens and G J Fleer ldquoStatistical theory of theadsorption of interacting chainmolecules 1 Partition functionsegment density distribution and adsorption isothermsrdquo TheJournal of Physical Chemistry vol 83 no 12 pp 1619ndash1635 1979

[35] M A Cohen Stuart G J Fleer and B H BijsterboschldquoAdsorption of poly(vinyl pyrrolidone) on silica IIThe fractionof bound segments measured by a variety of techniquesrdquoJournal of Colloid and Interface Science vol 90 no 2 pp 321ndash334 1982

[36] B K G Theng ldquoClay-polymer interactions summary andperspectivesrdquo Clay and Clay Minerals vol 30 no 1 pp 1ndash101982

[37] R I S Gill and T M Herrington ldquoThe flocculation of kaolinsuspensions with cationic polyacrylamides of varying molarmass but the same cationic characterrdquoColloids and Surfaces vol22 no 1 pp 51ndash76 1987

[38] R I S Gill and T M Herrington ldquoThe effect of surfacecharge on the flocculation of kaolin suspensions with cationicpolyacrylamides of varying molar mass but similar cationiccharacterrdquo Colloids and Surfaces vol 25 no 2ndash4 pp 297ndash3101987

[39] M A Cohen Stuart J M H M Scheutjens and G JFleer ldquoPolydispersity effects and the interpretation of polymeradsorption isothermsrdquo Journal of Polymer Science PolymerPhysics Edition vol 18 pp 559ndash573 1980

[40] K-Ch Ullman Stabilization of TiO2dispersion with non-ionic

water-soluble molecules [PhD thesis] University of Stuttgart1989

[41] H D Ackler R H French and Y-M Chiang ldquoComparisonsof Hamaker constants for ceramic systems with interveningvacuum or water from force laws and physical propertiesrdquoJournal of Colloid and Interface Science vol 179 no 2 pp 460ndash469 1996

[42] N K AdamThe Physics and Chemistry of Surfaces Dover NewYork NY USA 1968

[43] L Alagha S Wang L Yan Z Xu and J Masliyah ldquoSpectro-scopic investigation of the adsorption mechanisms of polyacry-lamide polymers onto iron oxide particlesrdquo Langmuir vol 29no 12 pp 3989ndash3998 2013

[44] S H Behrens M Borkovec and P Schurtenberger ldquoAggre-gation in charge-stabilized colloidal suspensions revisitedrdquoLangmuir vol 14 no 8 pp 1951ndash1954 1998

[45] C Friedsam A Del Campo Becares U Jonas M Seitzand H E Gaub ldquoAdsorption of polyacrylic acid on self-assembled monolayers investigated by single-molecule forcespectroscopyrdquoTheNew Journal of Physics vol 6 pp 9ndash16 2004

[46] D Grasso K Subramaniam M Butkus K Strevett and JBergendahl ldquoA review of non-DLVO interactions in environ-mental colloidal systemsrdquoReviews in Environmental Science andBiotechnology vol 1 no 1 pp 17ndash38 2002

[47] B E Novich and T A Ring ldquoColloid stability of clays usingphoton correlation spectroscopyrdquo Clays amp Clay Minerals vol32 no 5 pp 400ndash406 1984

[48] M Linsenbuhler J HWerth S M Dammer et al ldquoCluster sizedistribution of charged nanopowders in suspensionsrdquo PowderTechnology vol 167 no 3 pp 124ndash133 2006

[49] L Ghimici S Morariu and M Nichifor ldquoSeparation of claysuspension by ionic dextran derivativesrdquo Separation and Purifi-cation Technology vol 68 no 2 pp 165ndash171 2009

[50] R S Faibish M Elimelech and Y Cohen ldquoEffect of interpar-ticle electrostatic double layer interactions on permeate fluxdecline in crossflow membrane filtration of colloidal suspen-sions an experimental investigationrdquo Journal of Colloid andInterface Science vol 204 no 1 pp 77ndash86 1998

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



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CompositesJournal of

NanoparticlesJournal of



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Biomaterials


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Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



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MaterialsJournal of


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materials


Journal ofNanomaterials


Table 1 Physicochemical properties of AEROSIL OX 50 as per the manufacturer information

Source BET surface area PZC at pH SiO2Contents pH Primary particle size Tapped approximate densityEvonik Industries 50 + 15 (m2 gminus1) 32 ge998 38ndash48 04 (120583m) 130 (gL)ldquoPZC at pHrdquo signifies the PZC (point of zero charge) at pH at which surface charge of the particle is zero

particles and hence affect the stability of the dispersion[16] In addition to that the surface charge-to-mass ratioof the particle plays a very important role in stabilizingthe dispersion and this parameter is very much dependentupon the pH of the solution size of particles and so forthAlthough a number of research papers have been publishedto understand themechanism of adsorption of polymers overthe solid surfaces unfortunately none of the papers dealswith the prediction of adsorption behavior of a polymer overthe solid surface up to the required level [17 18]

Polyvinylpyrrolidone also named Povidone or PVP isa nonionic amphiphilic polymer Because of its exceptionalcombination of properties like low toxicity biocompatibilityfilm forming and adhesive characteristics complexing abilityto proton donors and low osmotic pressure it finds diverseapplications in various fields of life like pharmaceutical andcosmetic products food adhesives and textile auxiliaries ascompared to other water-soluble polymers like polyethyleneoxide and polyvinyl alcohol [19ndash21] In spite of these factsmechanisms involved in such processes are not well under-stood and hence need detailed and systematic exploration forproper utilization of silica [6 12ndash14 22] AEROSIL OX 50because of its physicochemical properties has a large numberof applications Among fumed silica AEROSIL OX 50 dueto its specific properties is widely used in biotechnologyagriculture medicine and pharmaceutics

Since surface modification of an oxide via polymeradsorption leads to a change in its physicochemical character-istics therefore the main objective of this work was to inves-tigate in detail the adsorption behavior of PVP onto silicain its aqueous suspension by using UV FTIR spectroscopyelectrophoresis and measurement techniques and to explorethe impact of particle size of silica temperature pretreatmentof adsorbent molecular mass of polymer and so forth on theadsorption phenomenon and to make use of that data for theexploration of the mechanism

2 Experimental

21 Materials AEROSIL OX 50 fumed silica oxide obtainedfrom Degussa Evonik Industries Germany was used as amodel substrate Some of the characteristics of AEROSILOX 50 are presented in Table 1 These properties were alsoverified by employing a mercury porosity meter (Autosorb-1der FirmaQuanta chrome USA) pH and LDmeasurementsand scanning electron microscopy The specific surface areareported by the manufacturer was 50 plusmn 15 (m2sdotgminus1) but whenmeasured it was 4072 (m2sdotgminus1)

Three different samples of PVP also known as Luvitecwere obtained from BASF Germany PVP had three differentmolar masses and was used as a stabilizer for the silicadispersion Some of the basic properties of PVP as provided

Table 2 Some of the basic properties of PVP as provided by themanufacturer BASF Germany

Sample PVP K17 PVP K30 PVP K90MwK dalton 7ndash11 45ndash55 1200ndash2000Degree of dispersity 18 plusmn 02 23 plusmn 02 34 plusmn 03Rel viscosity 1 in water 1075ndash1110 1201ndash1291 3991ndash6197

by the manufacturer are listed in Table 2 Water used for thedispersion was obtained fromMillipore GmbH SchwalbachGermany having pH around 65 and conductance of 25 120583S

22 Methods

221 Characterization of Silica Theparticle size and size dis-tribution of silica were determined using scanning electronmicroscope (Jowl Japan) and laser diffraction particle sizeanalyzer Mastersizer 2000 Malvern Co UK equipped withimpeller mixture The surface area of the material was esti-mated using mercury porosity meter (Autosorb-1 der FirmaQuanta chrome USA) Surface charge was measured usingZetasizer 3000 (Malvern Co Germany) The surface chargedensity 119902 in relation to pH was measured by polyelectrolytetitration using Particle ChargeDetector (PCDMutekGmbHGermany) FTIR Tensor Bruker Germany was used for IRspectra measurement

222 Pretreatment of Silica For this purpose the adsorbent(silica) was heated at five different temperatures from 298Kto 523K for three hours in a vacuum oven (Gallon KampUK) under inert atmosphere and then cooled to roomtemperature in a desiccant The sample so obtained was usedfor adsorption studies [23]

223 Characterization of Polymer The polymer was char-acterized by laser light scattering technique the instrumentused for the purpose was DAWN EOS supplied by WyattUSA with helium-neon laser of 6328 nmwavelength as lightsource

224 Adsorption Studies Polymer solution was preparedin water having concentration 0ndash80 ppm The solution wasmixed with 005 g of preheated adsorbent20mL of polymersolution in 100mL sample bottles for 3 hours at differenttemperatures The samples were equilibrated for 16 hours at298K at 85 rpm using orbital shaker (Sanyo Orbit Japan)Thereafter the supernatant was removed from samples bycentrifuging at 21000timesg for 15 minutes using centrifugemodel OSK12710 (Gawasieki Co Japan) and analyzed forpolymer concentration


AEROSIL OX 50


500 1000 1500 2000 2500 3000 3500 4000

00

02

04

06

08

10

Tran

smitt

ance

()













minus60

minus40

minus20

0

20

Zeta

pot

entia

l (m

V)

2 3 4 5 6 7 8 9 101pH



2
















120574119888= 119891(119904120590

120578119860119886) (3)







02 04 06 08 1000


0

5

10

15

20

25

30

35

Volu

me (

)



500 1000 1500 2000 2500 3000 3500 4000 4500

00

02

04

06

08

10 PVP

Tran

smitt

ance

()






000

002

004

006

008

010

Am

ount

adso

rbed

(mg

mminus2)






00

02

04

06

08

10

Am

ount

adso

rbed

(mg

mminus2)

10 20










Present


00000001

0000001

000001

00001

0001

Am

ount

adso

rbed

(mM

m2)




075

08

085

09

Am

ount

adso

rbed

(mg

m2)

minus60

minus40

minus20

0

20Ze

ta p

oten

tial

3 5 7 9 111pH




PVP K17PVP K30

PVP K90

04

05

06

07

08

09

Am

ount

adso

rbed

(mgmiddot

mminus2)

350 400 450 500 550300Temperature (K)






400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17




80

PVP K17PVP K30

PVP K90


minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)


H

N

Hn n


+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙









N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




AEROSIL OX 50


500 1000 1500 2000 2500 3000 3500 4000

00

02

04

06

08

10

Tran

smitt

ance

()













minus60

minus40

minus20

0

20

Zeta

pot

entia

l (m

V)

2 3 4 5 6 7 8 9 101pH



2
















120574119888= 119891(119904120590

120578119860119886) (3)







02 04 06 08 1000


0

5

10

15

20

25

30

35

Volu

me (

)



500 1000 1500 2000 2500 3000 3500 4000 4500

00

02

04

06

08

10 PVP

Tran

smitt

ance

()






000

002

004

006

008

010

Am

ount

adso

rbed

(mg

mminus2)






00

02

04

06

08

10

Am

ount

adso

rbed

(mg

mminus2)

10 20










Present


00000001

0000001

000001

00001

0001

Am

ount

adso

rbed

(mM

m2)




075

08

085

09

Am

ount

adso

rbed

(mg

m2)

minus60

minus40

minus20

0

20Ze

ta p

oten

tial

3 5 7 9 111pH




PVP K17PVP K30

PVP K90

04

05

06

07

08

09

Am

ount

adso

rbed

(mgmiddot

mminus2)

350 400 450 500 550300Temperature (K)






400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17




80

PVP K17PVP K30

PVP K90


minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)


H

N

Hn n


+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙









N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











120574119888= 119891(119904120590

120578119860119886) (3)







02 04 06 08 1000


0

5

10

15

20

25

30

35

Volu

me (

)



500 1000 1500 2000 2500 3000 3500 4000 4500

00

02

04

06

08

10 PVP

Tran

smitt

ance

()






000

002

004

006

008

010

Am

ount

adso

rbed

(mg

mminus2)






00

02

04

06

08

10

Am

ount

adso

rbed

(mg

mminus2)

10 20










Present


00000001

0000001

000001

00001

0001

Am

ount

adso

rbed

(mM

m2)




075

08

085

09

Am

ount

adso

rbed

(mg

m2)

minus60

minus40

minus20

0

20Ze

ta p

oten

tial

3 5 7 9 111pH




PVP K17PVP K30

PVP K90

04

05

06

07

08

09

Am

ount

adso

rbed

(mgmiddot

mminus2)

350 400 450 500 550300Temperature (K)






400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17




80

PVP K17PVP K30

PVP K90


minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)


H

N

Hn n


+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙









N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




000

002

004

006

008

010

Am

ount

adso

rbed

(mg

mminus2)






00

02

04

06

08

10

Am

ount

adso

rbed

(mg

mminus2)

10 20










Present


00000001

0000001

000001

00001

0001

Am

ount

adso

rbed

(mM

m2)




075

08

085

09

Am

ount

adso

rbed

(mg

m2)

minus60

minus40

minus20

0

20Ze

ta p

oten

tial

3 5 7 9 111pH




PVP K17PVP K30

PVP K90

04

05

06

07

08

09

Am

ount

adso

rbed

(mgmiddot

mminus2)

350 400 450 500 550300Temperature (K)






400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17




80

PVP K17PVP K30

PVP K90


minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)


H

N

Hn n


+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙









N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Present


00000001

0000001

000001

00001

0001

Am

ount

adso

rbed

(mM

m2)




075

08

085

09

Am

ount

adso

rbed

(mg

m2)

minus60

minus40

minus20

0

20Ze

ta p

oten

tial

3 5 7 9 111pH




PVP K17PVP K30

PVP K90

04

05

06

07

08

09

Am

ount

adso

rbed

(mgmiddot

mminus2)

350 400 450 500 550300Temperature (K)






400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17




80

PVP K17PVP K30

PVP K90


minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)


H

N

Hn n


+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙









N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




400 600 800 1000 1200 1400200Temperature (K)

04

05

06

07

08

09

10

11

Am

ount

adso

rbed

(mgmiddot

mminus2)

PVP K90PVP K30

PVP K17




80

PVP K17PVP K30

PVP K90


minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

minus5

0

Zeta

pot

entia

l (m

V)


H

N

Hn n


+

minus

CH2CH2 H2CH2C

∙∙

O∙∙∙∙N

∙∙O∙∙∙∙









N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




N

H

H

n


+

minus

CH2H2C

∙∙O∙∙

∙∙ N

Hn

+

minus

CH2H2C

∙∙O∙∙

∙∙O Si Si+120575+ 120575minus

H O120575+ 120575minus


Tran

smitt

ance

()

AEROSIL OX 50

PVP



500 1000 1500 2000 2500 3000 3500 4000



Competing Interests


Acknowledgments


References






























































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Adsorption of Polyvinylpyrrolidone over the Silica Surface…downloads.hindawi.com/journals/ijps/2016/2417292.pdf · 2019-07-30 · Research Article Adsorption of