Research Article Photoinitiated Polymerization of Cationic...

Research ArticlePhotoinitiated Polymerization of Cationic Acrylamide inAqueous Solution Synthesis Characterization and SludgeDewatering Performance

Huaili Zheng1 Yi Liao12 Meizhen Zheng1 Chuanjun Zhu3 Fangying Ji1

Jiangya Ma1 and Wei Fan1

1 Key Laboratory of the Three Gorges Reservoir Regionrsquos Eco-Environment State Ministry of EducationChongqing University Chongqing 400045 China

2Department of Architectural Engineering Sichuan University of Science and Engineering Zigong 643000 China3 China National Offshore Oil Corporation (CNOOC) Tianjin Chemical Research and Design Institute Tianjin 300131 China

Correspondence should be addressed to Yi Liao ly-001-1980163com

Received 18 August 2013 Accepted 17 November 2013 Published 5 February 2014

Academic Editors M Akgun A Ianniello J Jia and M Naushad

Copyright copy 2014 Huaili Zheng et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A copolymer of acrylamide (AM) with acryloyloxyethyl trimethyl ammonium chloride (DAC) as the cationic monomer wassynthesized under the irradiation of high-pressuremercury lampwith 22-azobis(2-amidinopropane) dihydrochloride (V-50) as thephotoinitiatorThe compositions of the photoinduced copolymer were characterized by Fourier transform infrared spectra (FTIR)ultraviolet spectra (UV) and scanning electron microscope (SEM) The effects of 6 important factors that is photo-initiatorsconcentration monomers concentration CO(NH

2)2(urea) concentrations pH value mass ratio of AM to DAC and irradiation

time on themolecular weight and dissolving time were investigatedThe optimal reaction conditions were that the photo-initiatorsconcentrationwas 03monomers concentrationwas 30wt irradiation timewas 60min urea concentrationwas 04 pH valuewas 50 and mass ratio of AM to DAC was 6 4 Its flocculation properties were evaluated with activated sludge using jar test Thezeta potential of supernatant at different cationic monomer contents was simultaneously measured The results demonstrated thesuperiority of the copolymer over the commercial polyacrylamide as a flocculant

1 Introduction

The fast industrialization rapid urbanization and unre-strained use and exploitation of natural resources throughoutthe world have increased the water pollution by differenttypes of pollutants [1 2] Treatment of the contaminatedwatergenerates large quantities of sludge as the negative by-product[3 4] Sludge treatments are based on both the stabilizationprocesses to block or reduce biological activity and ondewatering processes to reduce sludge volume [5] Generallyoperating cost for sludge treatment can take approximately50 of the total operating cost of the whole waste watertreatment plant [3 6] among which 30ndash50 is in relation tothe sludge dewatering [5] Hence it is necessary to improvewater removal efficiency of the sludge so that the cost of

sludge transportation and handling can be reduced as far aspossible [7]

Generally speaking moisture content of typical sewagesludge was up to 97ndash99 [8 9] Usually sludge dewateringis difficult even at high pressure considering the colloidaland compressible nature of sludge caused by the presence oforganic components mainly bacterial cells and EPS (extra-cellular polymeric substances) [7 10] Researches indicatedthat adding chemical conditioners such as flocculants andcoagulants can help the sludge particles agglomerate intolarger particles or flocs prior to solidndashwater separation [11]Because sludge is negatively charged the flocculants andcoagulants with positive charge are commonly used for thispurpose [10 12]

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 465151 11 pageshttpdxdoiorg1011552014465151

2 The Scientific World Journal

As a kind of organic flocculant cationic polyacrylamide(CPAM) can have the effect of charge neutralization andabsorption bridge in sludge dewatering [13] It has beenwidely used in sludge dewatering due to its outstandingadvantages such as low dosage demand high efficiency goodsolubility and being pollution free [14] The flocculationperformance of CPAM flocculants primarily depends onthe molecular weight and charge density [15] Furthermorethe level of molecular weight and charge density of CPAMdepend significantly on the type and amount of cationicmonomers involved in the process of synthesis Acryloy-loxyethyl trimethyl ammonium chloride (DAC) seems to beone of the most commonly used cationic commoner Com-pared with other frequently used cationic monomers such asmethacryloyloxyethyl trimethyl ammonium chloride (DMC)and dimethyldiallylammonium chloride (DMDAAC) DAChas its own unique advantages Because there is one lesshydrophobic methyl group in the carbon chain of DAC thanthat of DMC the hydrophilic and flexibility of the copolymerof acrylamide (AM) andDAC(P(AM-DAC)) should be betterthan those of the copolymer ofAMandDMC(P(AM-DMC))In addition P(AM-DAC) has higher cationic degree andmore reasonable cationic structure distribution than P(AM-DMDAAC) because the reactivity of DAC is significantlyhigher than that of DMDAAC Thus in this work DAC wasselected as the cationic monomer to synthesize with AMto prepare copolymer with molecular weight and cationicdegree as high as possible by testing and making decision onthe optimal reaction conditions

CPAM can be prepared by copolymerization of AMwith cationic monomers In general the most widely usedpolymerization reaction forAMand cationicmonomer is freeradical copolymerization in aqueous solution It can be initi-ated by heat [16] microwave [17 18] rays [19] and ultraviolet(UV) [20] In contrast with other methods photoinitiatedpolymerization has various advantages It can be carried outat low reaction temperature Low temperature is beneficialfor the production of polymer with high molecular weight byavoiding the side effect of branching and cross-linking whichcan be commonly encountered at high temperature [20ndash22]Meanwhile the photopolymerization is easy to operate andcontrol which requires only simple equipment economizedenergy sources making it an eco-friendly process [21] Inaddition photoinduced polymerization is believed to havethe ability to make surface modification on surface graftpolymerizations [23 24] However so far the most com-mon method to induce polymerization of AM and cationicmonomers is by heat There have been some reports on thesynthesis of P(AM-DAC) in aqueous solution induced byheat [25 26] but there are few reports currently on thesynthesis induced by UV light The existing studies about thepolymerization initiated by UV light are mostly concernedwith the microstructure and reaction kinetics of resultingcationic copolymers [27] and other similar polymerizationof P(AM-DAC) was carried out under the irradiation ofmetal halide lamps or low pressure mercury lamp [28 29]Considering the low efficiency of low pressure mercury lampand the high price ofmetal halide lampwe used high pressuremercury lamp to achieve high initiating efficiency and cost

saving Besides the report on flocculation performance of thepolymer induced by UV light is rarely mentioned thereforewe evaluated the sludge dewatering performance of thecopolymer induced byUV light compared with a commercialPAM

In this paper synthesis of the cationic polyacrylamideP(AM-DAC) was investigated using a novel initiation sys-tem photoirradiation 221015840-Azobis(2-amidinopropane) dihy-drochloride (V-50) was introduced into the system as thephotoinitiator for the polymerization of acrylamide withDAC as the cationic monomer in aqueous solutions Thephotoinitiator can initiate polymerization at low temperaturebecause the polymerizationwith photoinitiator does not haveany dependencies on reaction temperature Simultaneouslythe effects of the photoinitiators concentration monomersconcentration CO(NH

2)2(urea) concentration pH value

mass ratio of AM to DAC irradiation time on the molecularweight and dissolving time were investigated intensivelyStudy of the characterizations of the photoinitiated poly-mer P(AM-DAC) was realized by using such methods asFourier transform infrared spectra (FTIR) ultraviolet spectra(UV) and scanning electron microscope (SEM) Finallysludge dewatering experiment was carried out to evaluatethe dewatering efficiencies of the resulting polymers anda commercially available PAM Meanwhile the influencesof molecular weight and cationic monomer content of theresulting polymers on the sludge dewatering performancewere investigated

2 Experimental

21Materials ThemonomerAMwas industrialmaterial andused without further purification sourced from ChongqingLanjie Tap Water Company (Chongqing China) acryloy-loxyethyl trimethyl ammonium chloride (DAC) (80wt)was provided by Guangchuangjing Import and Export CoLtd Shanghai China EDTA (AR) and urea (AR) werepurchased from Chongqing Chuan-dong Chemical Co Ltd(Chongqing China) Photoinitiator 221015840-azobis(2-amidino-propane) dihydrochloride (V-50) was purchased from Rui-hong biological technology Co Ltd (Shanghai China)and other reagents were analytical grade used as receivedCommercial PAM was bought from Guanghui Chemical(Dalian China) (molecular weight provided by supplier was500 gsdotmolminus1 measured by our Lab was 460 gsdotmolminus1) Deion-ized water was used throughout this work High puritynitrogen was used in the synthesis of the polymer in orderto drive away the air existing in the reactor

22 Synthesis of the Copolymer P(AM-DAC) was synthe-sized from two monomers namely AM and DAC in anaqueous reaction system The reaction took place underUV irradiation and the specific procedure was shown stepby step as follows AM and DAC of varying dosages weredissolved in deionized water in the reaction vessel Themixture was stirred with a glass rod until the monomersdissolved completely Next a certain dosage of urea wasadded into the vessel The pH of the aqueous solution was

The Scientific World Journal 3

WaterWater

UV lamp

Quartz cold trapUV radiation

Reactor

N2N2

Figure 1 Photoinitiated reaction device

adjusted to designated values with 01M sodium hydroxideand 01M hydrochloric acid Purified nitrogen was bubbledthrough the aqueous solution at room temperature for about20min to remove the oxygen Then the photoinitiators wereadded into the solution The reaction vessel was sealed andtransferred to the photoinitiated reaction device (Figure 1)the core of which is a 500-W high pressure mercury lampThe irradiation time under UV lamp was set from 25minto 120min in a series of experiments The proposed reactionscheme for polymerization was shown in Scheme 1 Afterirradiation the photopolymerized products were removedfrom the reaction vessel and then purified with acetone andethanol followed by the process of drying breaking andpackaging

23 Characterization The Fourier transform infrared Spec-tra (FTIR) of the cationic polyacrylamide was measuredby the 550 Series II infrared spectrometer (Mettler ToledoInstruments Co Ltd Switzerland) the ultraviolet (UV)spectra of the cationic copolymer were detected by theTU-1901 double beam UV-visible light spectrophotometer(Beijing Puxi General Instrument Co Ltd China) Inaddition after pretreatment with spray gold morphology ofthe product was determined using VEGAII LMU scanningelectron microscopy (SEM) (TES-CAN Co Ltd of Chech)which was compared with that of the commercially availablePAM

24Measurement ofMolecularWeight The intrinsic viscosity([120578]) of the photoinduced polymer was determined in 1MNaCl aqueous solutionwith anUbbelohde viscometer at 30 plusmn005

∘CThe averagemolecular weight (Mw) of the copolymerwas calculated with the Mark-Houwink equation as follows[20]

Mw = 10000 times [120578]

373

1066

(1)

25 Measurement of Dissolving Time The dissolved time ofthe copolymer wasmeasured using the conductancemethodThe specific steps were as follows 100mL of distilled waterwas added to a 100mL beaker as the reaction vessel which

was placed in the water bath with magnetic stirring deviceThen the stir was started and the electrode of conductivitymeter was inserted into the beaker while the temperatureof the water bath was controlled at 30 plusmn 1∘C for 20minAfter that about 0038sim0042 plusmn 0001 g of the sample wasgradually blended in the distilled water If the conductancevalue did not change in 3minutes the sample was consideredcompletely dissolved Finally the time required for thecomplete dissolution of the sample was recorded

26 Sludge Dewatering Experiment To investigate the influ-ences of such conditions as molecular weight and cationicmonomer content of the resulting polymers on the sludgedewatering performance and evaluate the dewatering effi-ciencies of the photoinitiated copolymers and a commer-cially available PAM a program-controlled Jar-test apparatus(ZR4-6 ZhongrunWater Industry Technology DevelopmentCo Ltd China) was used for sludge dewatering experi-ments The sludge samples were obtained from the DadukouWastewater Treatment Plant located in Chongqing ChinaAll sludge samples were placed in 25-L polyethylene tanksand kept in the refrigerator at 4∘C after being transferredto the laboratory All experiments were carried out no laterthan three days after taking sludge samples to minimizepossible changes in sludge properties during storage Thesludge was characterized by a moisture content of 986mass density of 1002 kgsdotLminus1 and pH value of 73 500mLof sludge was transferred into beakers and then differentdosage of flocculant was addedThe stirring rate was 100 rpmcontinuing for 30 seconds to attain the complete mix ofthe flocculant with sludge followed by a 30 seconds slowstirring period at 50 rpm to promote floc growth Then theconditioned sludge was poured into a Buchner funnel forfiltering under a vacuum pressure of 009MPa for 30minor until the vacuum could not be maintained (in lt30min)The filterability of the sludge was measured by the filter cakemoisture content (FCMC)

FCMC =119872

119890minus119872

119889

119872

119890

times 100 (2)

where119872119890was the weight of filter cake at the end of filtration

and119872119889was the weight of filter cake after drying at 105∘C

Measurement Method for Zeta Potential A certain quantityof sludge supernate taken after dewatering was used forthe detection of zeta potential to evaluate the charge neu-tralization effect of the resulting polymers with analogousmolecular weight and various contents of cationic monomerThe electrophoretic mobility of these samples was measuredand then converted to the zeta potential value at roomtemperature using Malvern zetasizer Nano ZS90 (Malverninstruments Ltd UK)

3 Results and Discussion

31 Characterization of Copolymer Figure 2 was the FTIRspectra of the copolymerThe characteristic absorption bandsat 3462 cmminus1 and 1633 cmminus1 were assigned to the stretching


H2C H2CCH

CHCH

CH

O C O O

O

O

C

C

NH2

O C NH2

CH2 CH2

CH2

CH2

CH2

CH2

CH3

CH3

CH3

CH3

CH3

N+

N+

Clminus

Clminus

UV

initiator

Acrylamide Cationic monomer

m n

H3C

P(AM-DAC)

+

Scheme 1 Proposed reaction scheme of the synthesis

80

60

40

20

Tran

smitt

ance

()

4000 3000 2000 1000

Wavenumbers (cmminus1)

3462

2916

2864

1735

1633

1454 1348

1165

958

540

Figure 2 FTIR spectra of the copolymer (Mass ratio of AM toDACwas 6 4 average molecular weight of the photoinitiated copolymerwas 600 times 104 purified with ethanol and acetone for many timesbefore measurement)

vibration of ndashNH2and ndashC=O of ndashCONH

2groups in the

AM unit The characteristic absorption peaks at 2916 cmminus1and 2864 cmminus1 came from the ndashCH

3and ndashCH

2asymmetry

stretching vibration The characteristic absorption peak at958 cmminus1 arose from N+ (CH

3)3stretching vibration of

DAC unit The characteristic absorption peak at 1454 cmminus1was due to deformation vibration absorption of methylenegroup The characteristic absorption bands at 1735 cmminus1 and1165 cmminus1 were owe to the stretching vibration of C=O andCndashO in the DAC unit respectively All the above mentionedcharacteristic peaks were evidences that the two monomerswere copolymerized

The UV spectra of the photoinitiated copolymer P(AM-DAC) acrylamide and DAC were presented in Figure 3as the curves (a) (b) and (c) respectively Because thefeed concentration of photoinitiators was very slow and

Abso

rban

ce

180 200 220 240 260 280 300

Wavelength (nm)

AM

DAC

P(AM-DAC)

Figure 3 UV spectra of (a) P(AM-DAC) (Mass ratio of AM toDACwas 6 4 average molecular weight of the photoinitiated copolymerwas 600 times 104) (b) acrylamide and (c) DAC

the copolymer was purified with acetone and ethanol formany times the concentration of residual photoinitiatorwould be much lower Thus the UV absorbance of thephotoinitiator that remained in copolymer could be ignoredas there was no obvious UV absorbance in the range of190ndash300 nm in our test It was observed that there werestrong absorption peaks at 1985 nmand 198 nm formonomerAM and DAC respectively which was consistent with thereport that the absorption peak of UV spectra of 120572 120573-unsaturated amides with no substitute for their N atoms wasat around 200 nm [30] From Figure 3(a) we also found thatthere were three strong absorption peaks at about 200 nm233 nm and 280 nm for the photoinitiated copolymer Thepeak at 200 nm probably resulted from the residual AM inthe completed reaction while the new absorption peak at233 nm and 280 nm proved the generation of a new material


in the resulting polymer which was an evidence that thecopolymerization of AM and DAC took place under theirradiation of UV lamp

Figure 4 showed the surfacemorphology of commerciallyavailable PAM and photoinitiated P(AM-DAC) As shownin Figure 4 close cross-linking and gel network structurewere observed in the photoinitiated P(AM-DAC) whereasthe commercial PAM showed a comparatively looser andflatter surface The difference in morphological structuremay result from the introduction of DAC and some kind ofsurface modification induced by ultraviolet light which wasprobably similar to existing related reports [21 23 24] Thenet structure of photo-induced copolymer was favorable forthe penetration of water into the polymeric network so thatthe solubility of product could be improved [31] Meanwhilethe net structure was conducive for the improvement ofthe ability of adsorption and bridging of P(AM-DAC) andmore colloidal particles organic pollutants in water couldbe adsorbed accordingly Additionally the average fractaldimension which was the slope of the fitted straight lineto Ln(A) (area) as a function of Ln(L) (perimeter) wascalculated using Image-pro Plus 60 Software to quantitativelyestimate the surface morphology of samples [32] The resultsshowed that the fractal dimensions of commercial PAM andphotoinitiated P(AM-DAC) were 15911 and 16398 respec-tively

32 Effect of Photoinitiators Concentration As is shown byFigure 5 themolecular weight increased as the initiators con-centration rose from 01 to 03 and decreased with furtherincrease in the initiators concentration This phenomenoncould be explained by the cage effect and primary radicaltermination with stable large molecules When the photoini-tiators concentration was relatively low cage effect may leadto low polymer yields and low average molecular weights dueto predominating termination of the growing chains insidethe cage as there were fewer monomer units to contributepropagation [33 34] As the initiator increased from 01 to03 more and more primary radicals were generated andmore and more of them could escape from their ldquocagesrdquo toreact with monomers leading to continuing growth of themolecular weight in this process However further increasein initiators concentration above 03 might increase thetermination and chain transfer rate which led to the decreaseof molecular weight This trend accorded with the classicalkinetic theory which predicts that the kinetic chain lengthdepends on the square root of the initiator concentrationas also indicated by most of the previous works [35 36]In addition because of the light absorption of initiatorand scattering effect in reaction medium the light intensitydecreased along the radiation path This variance would leadto the spatially inhomogeneous distribution of free radicals inthe system so that the conversion rate and molecular weightof various layers in the reaction vessel were different Thiswas different from the heat-induced polymerization whichwas characterized with uniform active center distributionand reaction speed It had been reported that polymer withultrahigh molecular weight was readily prepared in photo-induced polymerization due to the graded distribution of

light intensity within reaction vessel [37] Besides Figure 5showed that the change of dissolving time was consistentwith the change of molecular weight which indicated thatdissolving time relied mainly on the molecular weight ifthere was little cross-linking in the process of polymerizationTherefore the favorable value of the initiators concentrationwas 03

33 Effect of Monomers Concentration As shown in Figure 6the molecular weight and dissolving time increased at thebeginning and then decreased with increasing monomersconcentration The initial monomers concentration wasimportant partly because the free radical number was deter-mined by the monomers concentration at the start of thereaction [20] When the monomers concentration was quitelow the production rate of the free radicals was so slowthat a low free radical concentration existed These freeradicals might be more prone to premature terminationbecause of the cage effect as previously mentioned [38]In addition there was comparatively less possibility of con-tact and collision between monomers of AM and DAC atlow monomers concentration which was not conducive tothe growth of the molecular chain Thus low molecularweight was typical at low monomers concentration As themonomers concentration increased from 15wt to 30wta sharp increase in molecular weight was observed Thistrend could be explained as the consequences of weakenedcage effect and increased probability of contact and collisionbetween monomers at increasing monomers concentrationThis process indicated that photo-induced polymerizationcould still be accounted for by the general law of free radicalpolymerization that is the kinetic chain length is propor-tional to the monomers concentration However with thefurther increase in monomers concentration the molecularweight decreased This could be explained as follows first alarger generation of heat released by the highly exothermicreactions and the lower thermal diffusivity of the reactingmixture at relatively high monomers concentration led totemperature rise of reaction system which would lower thedegree of polymerization and second the higher viscosityof the system and the consequently low rate of diffusion-controlled termination at relatively high monomers concen-tration (ie the gel effect) caused uncontrollable reactionsand low molecular weight [39 40] Moreover the change ofdissolving time was consistent with the change of molecularweight and the trend could be explained by the fact thatcopolymer with high molecular weight dissolves more slowlyin water Therefore 30wt was adopted as the optimalconcentration of monomers concentration

34 Effect of Irradiation Time It can be seen from Figure 7that the molecular weight increased sharply at the beginningwith the increase of irradiation time and kept constant after60min It was consistent with the basic characteristics offree radical polymerization slow initiation fast propagationand rapid termination At the beginning of the reactionthe medium was transparent and the UV light could eas-ily transfer through the medium in which water-solublephotoinitiator could absorb the light and produced a large


10

8

6

4

2

2 3 4 5 6 7 8

ln(A

)

ln(L)

n = 133

R2= 0954

ln(A) = 15911ln(L) minus 15897

(a)

10

8

6

4

2

2 3 4 5 6 7

ln(A

)

ln(L)

n = 137

R2= 0971

ln(A) = 16398ln(L) minus 16953

(b)

Figure 4 SEM micrographs of (a) commercial PAM and (b) photoinitiated P(AM-DAC) (Mass ratio of AM to DAC was 6 4 averagemolecular weight of photoinitiated-copolymer was 600 times 104 purified with ethanol and acetone for many times before measurement)


00 02 04 06 08 10400

500

600

700

800

Molecular weightDissolving time

Photoinitiators concentration ()

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104

Figure 5 Effect of photoinitiators concentration on the molecularweight and dissolving time (Polymerization conditions monomersconcentration was 30wt mass ratio of AM to DAC was 6 4 ureaconcentration was 04 pH value was 50 and irradiation time was60min)

15 20 25 30 35 40

150

300

450

600

750

900


40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Monomers concentration (wt)

Mol

ecul

ar w

eigh

t

times104

Figure 6 Effect of monomers concentration on the molecularweight and dissolving time (Polymerization conditions photoini-tiators concentration was 03 mass ratio of AM to DAC was 6 4urea concentration was 04 pH value was 50 and irradiation timewas 60min)

number of free radicals in a short time at the surfaceand subsurface of the medium and in turn initiate poly-merization reaction between AM and cationic monomersAs the irradiation time increased the transparent solutiongradually turned into a gelatinous texture leading to theweakened penetration of UV light through the reaction ves-sel Besides that the possibility of chain transfer reaction anddisproportionation reaction increased as the irradiation timeincreased As a result there was no further increase of degree

20 40 60 80 100 12000

100

200

300

400

500

600

700

Irradiation time (min)


40

20

0

60

80

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104

Figure 7 Effect of irradiation time on the molecular weightand dissolving time (Polymerization conditions photoinitiatorsconcentration was 03 monomers concentration was 30wtmass ratio of AM to DAC was 6 4 urea concentration was 04pH value was 50)

of polymerization in the late stage of polymerization andmolecular weight remained almost unchanged after reachingthe maximum at 60min accordingly Some studies reportedthat the time taken to reach the maximum molecular weightof polyacrylamide in aqueous polymerization initiated byheat was over 50 h [41] Obviously it was much higher thanthe polymerization time initiated by UV light In additionsimilar results were also reported in dispersion polymer-ization [42] In this sense the polymerization initiated byUV light was more energy efficient and more effective thanpolymerization initiated by heat Meanwhile the dissolvingtime of the photoinitiated polymer increased all the timeof the reaction It may result from the high degree ofcrosslinking with longer reaction time Consequently 10 hwas adopted as the optimal irradiation time

35 Effect of Urea Concentration In the actual applicationsboth highmolecular weight and good solubility are the favor-able characteristics of CPAM as flocculants However thedissolution rate of polymer is very slow because it is difficultfor water to seep into the polymer due to the significantdifferences of size and velocity between water and polymerAccording to the theory of instant dissolution the dissolutionrate of a polymer can be accelerated when it contained somemicromolecules with a structure similar to the polymerBecause both acrylamide and urea contain amide groupurea is widely used in the synthesis of polyacrylamide toimprove the dissolution rate of the polymer Urea can weakenthe hydrogen bonding of the molecular chain within CPAMbecause the active amide groups in urea will react with theamide group in polymer which will cause the decrease of theintermolecular forces and the chance of crosslinking [9 43]Figure 8 showed that themolecular weight increased slowly at


00 01 02 03 04 05

550

600

650

700

750

800

Urea concentration ()


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)Figure 8 Effect of urea concentration on the molecular weightand dissolving time (Polymerization conditions photoinitiatorsconcentration was 03 monomers concentration was 30wtmass ratio of AM toDACwas 6 4 pH value was 50 and irradiationtime was 60min)

the urea concentration ranging from 005 to 04 and thendecreased sharply at the urea concentration above 04 Thehighest molecular weight of 800 times 104 was obtained when theconcentration of urea was equivalent to 04 The changesof molecular weight can be interpreted as follow besidesa solubilizer urea can take part in oxidation-reductionreactions as a reducing agent at lowurea concentrationwhichwould benefit the increase of kinetic chain length and themolecular weight increased accordingly However with thefurther increase of urea concentration the probability ofchain transfer increased which was not desired for preparinga polymer with highmolecular weight [6] In addition excessurea may affect the quality of the product Figure 8 alsoshowed that the dissolving time of CPAM continued todrop as the concentration of urea increased from 005 to050 and the dissolving time of CPAM was 75min at themaximum molecular weight Based on the discussion theoptimal concentration of urea was 04

36 Effect of pH Value The effect of pH on molecular weightand dissolving time was shown in Figure 9 The pH valuevaried from 3 to 9 in this experiment It was found that boththemolecularweight anddissolving time increased firstly andthen decreased In strong acidic conditions the intramolecu-lar and intermolecular imidization reaction occurred easilydue to the amide bond in acrylamide resulting in thecrosslinking between polymers which is one of the mostimportant reasons leading to lowmolecular weight and weaksolubility of CPAM [27] While under alkali conditions ahydrolysis of CPAM would take place to produce NH

3or

NH3sdotH2O which will then react with acrylamide to form

Nitrilotripropionamide [N(CH2CH2CONH

2)3] NTP NTP

as a reducing agent and chain transfer agent would lead

400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9

Figure 9 Effect of pH value on the molecular weight and dissolvingtime (Polymerization conditions photoinitiators concentrationwas03 monomers concentration was 30wt mass ratio of AM toDAC was 6 4 urea concentration was 04 and irradiation timewas 60min)

to polymerization termination or chain transfer with lowmolecular weight [44]Moreover the reaction solutionwouldacquire increasing amounts of negative charges as the pHvalue increased resulting in the increased electrostatic repul-sion between radicals or the changes of mobility flexibilityand configuration in the polymer solvents [45] In additionFigure 9 showed that the dissolving time was 83min if the pHwas 5 In general weak acidic environment was ideal for thepolymerization reaction and pH 5was adopted as the optimalcondition

37 Effect of the Mass Ratio of AM to DAC Compared withPAM CPAM has not only the adsorption bridging effectbut also charge neutralization effect on sludge dewateringdue to the adding of cationic monomers to PAM As shownin Figure 10 both molecular weight and the dissolvingtime decreased all the time as the mass ratio of AM toDAC decreased from 8 2 to 3 7 Prior research showedthat the reactivity ratios of AM and DAC were 22864 and03835 respectively indicating that the reactivity of AMwas higher than that of DAC [25] Thus copolymer withhigher molecular weight could be prepared readily withhigher dosage of AM When the amount of DAC increasedthe time required to polymerization increased due to thelow reactivity of DAC resulting in the increased time athigh temperature High temperature led to the increase ofchain transfer rate constant of acrylamide in solution Inaddition cationic groups such as quaternary ammoniumgroups existing in DAC had space hindered effect which willhamper the diffusion of monomer to the polymer [38] Sothe molecular weight of copolymer decreased with the DACincreased Furthermore the decrease of dissolving time ofCPAM with the increase of DAC content can be explained


Table 1 Contrast of sludge dewatering performances of several CPAMs with analogous molecular weight and various contents of DAC

Samples number Mass ratio of AM toDAC

Molecular weight(times104) gsdotmolminus1

Zeta potentialmV

Filter cake moisturecontent

1 10 0 560 minus189 7782 8 2 550 minus104 7433 7 3 500 minus56 7024 6 4 530 minus129 6365 5 5 480 167 689The analogous molecular weight of copolymers was attained by adding various dosages of the photo-initiator the dosage of all samples was 15 gsdotkgminus1 sludgedry matter the concentration of polymer solution was 01

150

300

450

600

750

900

Mass ratio of AM and DAC

40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7

Figure 10 Effect of mass ratio of AM to DAC on the molecu-lar weight and dissolving time (Polymerization conditions pho-toinitiators concentration was 03 monomers concentration was30wt urea mass concentration was 04 pH value was 50 andirradiation time was 60min)

as follows DAC is a quaternary ammonium salt and itsmonomer and homopolymer could dissolve in water readily[46] After DACwas synthesized with AM the hydrophilicityof PAM could be greatly improvedWhen combined with thesubsequent sludge dewatering experiment the optimal massratio of AM to DAC was 6 4 in this study

38 Sludge Dewatering Performance In order to evaluatethe flocculation effect of the copolymer prepared by thephotoinitiated polymerization on sludge dewatering themoisture content of the filter cake and zeta potential wasmeasured Figure 11 showed the effects of photoinitiatedP(AM-DAC) with same mass ratio (mAM mDAC = 6 4) anddifferent molecular weight (200 400 600 times 104 gsdotmolminus1) andcommercial PAMonfilter cakemoisture content with variousdosages It indicated that the filter cake moisture contentdecreased firstly with the increase of flocculant dosage andincreased slowly when the flocculant dosage above 15 gsdotkgminus1sludge dry matter The lower filter cake moisture contentcould be achieved using the synthesized copolymer thus thesynthesized CPAMsweremore effective than the commercial

100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)

Commercial PAMMw = 200 times 10

4

Mw = 400 times 104

Mw = 600 times 104

Dosage (gmiddotkgminus1) sludge dry matter

Figure 11 Contrast of dewatering efficiencies of several synthesizedCPAMs and commercial PAM on filter cake moisture content atdifferent dosages (The mass ratio of AM to DAC of the synthesizedCPAMswas 6 4 molecular weights of the synthesized CPAMswere200 400 and 600 times 104 gsdotmolminus1 respectively the various molecularweights of the copolymers were obtained by adding various dosagesof the photoinitiator the concentration of polymer solution was01)

PAM in sludge dewatering In addition for synthesizedCPAMs the lower filter cake moisture content could beachievedwith the highermolecularweight polymer under thesame dosage of flocculant It indicated that the polymer withhigher molecular weight had better absorption and bridgeeffect

Table 1 listed the contrast results of sludge dewateringperformances of several CPAMs with analogous molecularweight and various contents ofDACConsidering the absorp-tion bridging effect of a polymer that depends mainly onthe molecular weight of the polymer keeping the molecularweight of the polymers analogous in this study could behelpful for us to diminish the differences in bridging effectof various polymers in order to evaluate the effect of cationicmonomer content of polymer on sludge dewatering moreaccurately As shown in the table the zeta potential increasedsharply until the value went above 0 A reverse of the netcharge was observed with the increase of cationic monomer


content in this experiment Meanwhile the moisture contentof the filter cake decreased when the mass ratio changedfrom 10 0 to 6 4 and then increasedThephenomenon couldbe explained as follows as the cationic monomer contentincreased the electrostatic repulsion among the polymerchains increased leading to the better stretching of thepolymer chain which was conducive to the enhancementof the bridging effect of the polymer on sludge particlesBesides the effect of charge neutralization of the polymeron the sludge particles with negatively charge increasedwith the increasing cationic monomer content thus thesurface charge of the sludge particles shifted gradually fromnegative values to zero as evidenced by the zeta potential dataresulting in the reduced electrostatic repulsive force amongthe sludge particles which benefitted the sludge particles toagglomerate into larger particles or flocs [39]When themassratio of DAC to AM increased to 5 5 the particle surface ofsludge turned into positively charged and repulsion betweenparticles increased thus the filter cake moisture contentincreased

4 Conclusions

The photoinitiated copolymer of acrylamide with acry-loyloxyethyl trimethyl ammonium chloride (DAC) as thecationic monomer was synthesized for sludge dewateringwith 22-azobis(2-amidinopropane)dihydrochloride (V-50)as the photoinitiator FTIR and UV spectra showed that thesynthesized product was a copolymer of AM and DAC SEMimages provided the surface morphology of the copolymer

The optimal reaction conditions for preparing photo-induced P(AM-DAC) were as follows photoinitiators con-centration was 03 monomers concentration was 30wtthe irradiation time was 60min urea concentration was04 pH value was 50 and the mass ratio of AM to DACwas 6 4

The sludge dewatering experiment at various molecularweights and various cationicmonomer contents of the photo-induced copolymer demonstrated the superiority of thecopolymer product over PAM as a flocculant and bothabsorption bridging and charge neutralization played impor-tant roles in the sludge dewatering process of the photo-induced copolymer

Conflict of Interests

The authors declare that all of them have seen and approvedthe submission of this paper to this journal and there is noconflict of interests regarding the publication of this paper

Acknowledgments

The authors are grateful for the financial support provided bythe National Natural Science Foundation of China (Projectno 21177164) and the Cultivation Fund of the Key Scientificand Technical Innovation Project Ministry of Education ofChina (no 708071)

References

[1] M Naushad ldquoSurfactant assisted nano-composite cationexchanger development characterization and applications forthe removal of toxic Pb2+ from aqueous mediumrdquo ChemicalEngineering Journal vol 235 pp 100ndash108 2014

[2] M Naushad Z AL-Othman andM Islam ldquoAdsorption of cad-mium ion using a new composite cation-exchanger polyanilineSn (IV) silicate kinetics thermodynamic and isotherm studiesrdquoInternational Journal of Environmental Science and Technologyvol 10 pp 567ndash578 2013

[3] B Peeters R Dewil L Vernimmen B van den Bogaert and IY Smets ldquoAddition of polyaluminiumchloride (PACl) to wasteactivated sludge to mitigate the negative effects of its stickyphase in dewatering-drying operationsrdquoWater Research vol 47no 11 pp 3600ndash3609 2013

[4] Z Zhang S Xia and J Zhang ldquoEnhanced dewatering of wastesludge with microbial flocculant TJ-F1 as a novel conditionerrdquoWater Research vol 44 no 10 pp 3087ndash3092 2010

[5] T Ruiz T Kaosol and C Wisniewski ldquoDewatering of urbanresidual sludges filterability and hydro-textural characteristicsof conditioned sludgerdquo Separation and Purification Technologyvol 72 no 3 pp 275ndash281 2010

[6] J Boran L Houdkova and T Elsaszliger ldquoProcessing of sewagesludge dependence of sludge dewatering efficiency on amountof flocculantrdquoResources Conservation andRecycling vol 54 no5 pp 278ndash282 2010

[7] A Mahmoud J Olivier J Vaxelaire and A F A HoadleyldquoElectro-dewatering ofwastewater sludge influence of the oper-ating conditions and their interactions effectsrdquoWater Researchvol 45 no 9 pp 2795ndash2810 2011

[8] G Zhen X Yan H Zhou H Chen T Zhao and Y ZhaoldquoEffects of calcined aluminum salts on the advanced dewateringand solidificationstabilization of sewage sludgerdquo Journal ofEnvironmental Sciences vol 23 no 7 pp 1225ndash1232 2011

[9] J Ma H Zheng M Tan et al ldquoSynthesis characterization andflocculation performance of anionic polyacrylamide P (AM-AA-AMPS)rdquo Journal of Applied Polymer Science vol 129 no 4pp 1984ndash1991 2013

[10] H Saveyn G Pauwels R Timmerman and P van der MeerenldquoEffect of polyelectrolyte conditioning on the enhanced dewa-tering of activated sludge by application of an electric fieldduring the expression phaserdquoWater Research vol 39 no 13 pp3012ndash3020 2005

[11] YQi K BThapa andA F AHoadley ldquoApplication of filtrationaids for improving sludge dewatering propertiesmdasha reviewrdquoChemical Engineering Journal vol 171 no 2 pp 373ndash384 2011

[12] D Curvers K C Maes H Saveyn B de Baets S Miller and Pvan der Meeren ldquoModelling the electro-osmotically enhancedpressure dewatering of activated sludgerdquo Chemical EngineeringScience vol 62 no 8 pp 2267ndash2276 2007

[13] T P Nguyen N Hilal N P Hankins and J T Novak ldquoChar-acterization of synthetic and activated sludge and conditioningwith cationic polyelectrolytesrdquo Desalination vol 227 no 1ndash3pp 103ndash110 2008

[14] J Wang C Chen Q Gao T Li and F Zhu ldquoRelationshipbetween the characteristics of cationic polyacrylamide andsewage sludge dewatering performance in a full-scale plantrdquoProcedia Environmental Sciences vol 16 pp 409ndash417 2012

[15] J Zhu H Zheng Z Jiang et al ldquoSynthesis and character-ization of a dewatering reagent cationic polyacrylamide (P(AM-DMC-DAC)) for activated sludge dewatering treatmentrdquo


Desalination and Water Treatment vol 51 no 13ndash15 pp 2791ndash2801 2013

[16] Z L Yang B Y Gao C X Li Q Y Yue and B Liu ldquoSynthesisand characterization of hydrophobically associating cationicpolyacrylamiderdquo Chemical Engineering Journal vol 161 no 1-2 pp 27ndash33 2010

[17] S Pal S Ghorai M K Dash S Ghosh and G Udayab-hanu ldquoFlocculation properties of polyacrylamide grafted car-boxymethyl guar gum (CMG-g-PAM) synthesised by conven-tional and microwave assisted methodrdquo Journal of HazardousMaterials vol 192 no 3 pp 1580ndash1588 2011

[18] Y Wei F Cheng and H Zheng ldquoSynthesis and flocculatingproperties of cationic starch derivativesrdquo Carbohydrate Poly-mers vol 74 no 3 pp 673ndash679 2008

[19] J-P Wang Y-Z Chen X-W Ge and H-Q Yu ldquoGammaradiation-induced grafting of a cationic monomer onto chi-tosan as a flocculantrdquoChemosphere vol 66 no 9 pp 1752ndash17572007

[20] Y Wu and N Zhang ldquoAqueous photo-polymerization ofcationic polyacrylamide with hybrid photo-initiatorsrdquo Journalof Polymer Research vol 16 no 6 pp 647ndash653 2009

[21] B Kordoghli R Khiari M F Mhenni F Sakli and M NBelgacem ldquoSulfonation of polyester fabrics by gaseous sulfuroxide activated by UV irradiationrdquo Applied Surface Science vol258 no 24 pp 9737ndash9741 2012

[22] V Bernabe-Zafon M Beneito-Cambra E F Simo-Alfonsoand J M Herrero-Martınez ldquoComparison on photo-initiatorsfor the preparation of methacrylate monolithic columns forcapillary electrochromatographyrdquo Journal of ChromatographyA vol 1217 no 19 pp 3231ndash3237 2010

[23] J Deng L Wang L Liu and W Yang ldquoDevelopments andnew applications of UV-induced surface graft polymerizationsrdquoProgress in Polymer Science vol 34 no 2 pp 156ndash193 2009

[24] K H Hong N Liu and G Sun ldquoUV-induced graft poly-merization of acrylamide on cellulose by using immobilizedbenzophenone as a photo-initiatorrdquo European Polymer Journalvol 45 no 8 pp 2443ndash2449 2009

[25] W Ding Y Tao G Qu and Y Zhang ldquoInvestigation of thereactivity ratios of acrylamide and 2-acyloyloxyethyl trimethy-lammonium chloride copolymerizationrdquo Chinese Journal ofApplied Chemistry vol 4 no 26 pp 392ndash395 2009

[26] H Zheng L Li Y Yu X Tang Y Yang and S Zhang ldquoSynthesisof cationic polyacrylamide flocculant for sludge dewateringrdquoChemical Industry and Engineering Progress vol 27 no 4 pp564ndash568 2008

[27] W Li T Yao and Y Zheng ldquoReactivity ratio determination andsequence-length distribution of AMDAC copolymerizationinitiated by photosensitizerrdquo Polymer Materials Science andEngineering vol 28 no 5 pp 61ndash65 2012

[28] F-S Liu Z-W Li and S-T Yu ldquoCopolymerization of 2-methylacryloyloxyethyltrimethylammonium chloride andacrylamide assisted by photo-initiationrdquo Polymeric MaterialsScience and Engineering vol 26 no 2 pp 22ndash25 2010

[29] W Li T Yao S Liu and Y Zheng ldquoThe synthesis ofhigh molecular weight polyacrylamide-2-acryloyloxyethyltri-methylammonium chloride initiated by photosensitizerrdquo Jour-nal of Taiyuan University of Technology vol 42 no 3 pp 273ndash276 2011

[30] Y-C Ye H-M Tan J-L Zhang and Y-W Guo ldquoStudy on theultraviolet spectra of diacetone acrylamiderdquo Spectroscopy andSpectral Analysis vol 28 no 6 pp 1356ndash1358 2008

[31] F A Aouada B-S Chiou W J Orts and L H CMattoso ldquoPhysicochemical morphological properties ofpoly(acrylamide) methylcellulose hydrogels effects of mono-mer crosslinker and polysaccharide compositionsrdquo PolymerEngineering and Science vol 49 no 12 pp 2467ndash2474 2009

[32] G Zhu H Zheng Z Zhang T Tshukudu P Zhang and XXiang ldquoCharacterization and coagulation-flocculation behav-ior of polymeric aluminum ferric sulfate (PAFS)rdquo ChemicalEngineering Journal vol 178 pp 50ndash59 2011

[33] S Noppakundilograt P Nanakorn W Jinsart and S Kiat-kamjornwong ldquoSynthesis of acrylamideacrylic acid-based alu-minum flocculant for dye reduction and textile wastewatertreatmentrdquo Polymer Engineering and Science vol 50 no 8 pp1535ndash1546 2010

[34] D S Achilias and C Kiparissides ldquoDevelopment of a generalmathematical framework for modeling diffusion-controlledfree-radical polymerization reactionsrdquoMacromolecules vol 25no 14 pp 3739ndash3750 1992

[35] K Venkatarao and M Santappa ldquoUranyl ion-sensitized poly-merization of acrylamide and methacrylamide in aqueoussolutionrdquo Journal of Polymer Science A vol 5 no 3 pp 637ndash649 1967

[36] Z Yuan and H Hu ldquoPreparation and characterization ofcrosslinked glyoxalated polyacrylamide paper-strengtheningagentrdquo Journal of Applied Polymer Science vol 126 supplement1 pp E459ndashE469 2012

[37] Y Yan L Liu and W Yang ldquoStudy on photoinitiated precipita-tion polymerization of acrylamiderdquo Journal of Beijing Universityof Chemical Technology vol 34 no 4 pp 393ndash400 2007

[38] XWangQYue BGaoX Si X Sun and S Zhang ldquoDispersioncopolymerization of acrylamide and dimethyl diallyl ammo-nium chloride in ethanol-water solutionrdquo Journal of AppliedPolymer Science vol 120 no 3 pp 1496ndash1502 2011

[39] G R Chang J C Liu and D J Lee ldquoCo-conditioning anddewatering of chemical sludge and waste activated sludgerdquoWater Research vol 35 no 3 pp 786ndash794 2001

[40] X Peng Z Tao and X Peng ldquoWater-soluble copolymers VSynthesis of low molecular weight amphoteric polyacrylamideby foamed copolymerizationrdquo Journal of Applied Polymer Sci-ence vol 118 no 1 pp 159ndash164 2010

[41] H Zheng Y You X Deng et al ldquoSynthesis of a cationicpolyacrylamide with high molecular weight and high purityrdquoChinese Journal of Environmental Engineering vol 6 no 4 pp1675ndash1680 2012

[42] W Wang L Liu Z Huang and W Yang ldquoStudy on pho-toinitiated dispersion polymerization of acrylamide by usingpoly(acrylic acid)-graft-nonylphenoxypoly-(ethylene oxide) asthe dispersantrdquoActa Polymerica Sinica no 3 pp 320ndash326 2005

[43] R Zangi R Zhou and B J Berne ldquoUrearsquos action on hydropho-bic interactionsrdquo Journal of the American Chemical Society vol131 no 4 pp 1535ndash1541 2009

[44] H Zhou RHuC Chen andT Li ldquoSynthesis and application ofanionic polyacrylamiderdquo Speciality Petrochemicals vol 23 no 2pp 4ndash7 2006

[45] H-R Lin ldquoSolution polymerization of acrylamide using potas-sium persulfate as an initiator kinetic studies temperature andpH dependencerdquo European Polymer Journal vol 37 no 7 pp1507ndash1510 2001

[46] J P Wang S J Yuan Y Wang and H Q Yu ldquoSynthesischaracterization and application of a novel starch-based floccu-lant with high flocculation and dewatering propertiesrdquo WaterResearch vol 47 no 8 pp 2643ndash2648 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


As a kind of organic flocculant cationic polyacrylamide(CPAM) can have the effect of charge neutralization andabsorption bridge in sludge dewatering [13] It has beenwidely used in sludge dewatering due to its outstandingadvantages such as low dosage demand high efficiency goodsolubility and being pollution free [14] The flocculationperformance of CPAM flocculants primarily depends onthe molecular weight and charge density [15] Furthermorethe level of molecular weight and charge density of CPAMdepend significantly on the type and amount of cationicmonomers involved in the process of synthesis Acryloy-loxyethyl trimethyl ammonium chloride (DAC) seems to beone of the most commonly used cationic commoner Com-pared with other frequently used cationic monomers such asmethacryloyloxyethyl trimethyl ammonium chloride (DMC)and dimethyldiallylammonium chloride (DMDAAC) DAChas its own unique advantages Because there is one lesshydrophobic methyl group in the carbon chain of DAC thanthat of DMC the hydrophilic and flexibility of the copolymerof acrylamide (AM) andDAC(P(AM-DAC)) should be betterthan those of the copolymer ofAMandDMC(P(AM-DMC))In addition P(AM-DAC) has higher cationic degree andmore reasonable cationic structure distribution than P(AM-DMDAAC) because the reactivity of DAC is significantlyhigher than that of DMDAAC Thus in this work DAC wasselected as the cationic monomer to synthesize with AMto prepare copolymer with molecular weight and cationicdegree as high as possible by testing and making decision onthe optimal reaction conditions

CPAM can be prepared by copolymerization of AMwith cationic monomers In general the most widely usedpolymerization reaction forAMand cationicmonomer is freeradical copolymerization in aqueous solution It can be initi-ated by heat [16] microwave [17 18] rays [19] and ultraviolet(UV) [20] In contrast with other methods photoinitiatedpolymerization has various advantages It can be carried outat low reaction temperature Low temperature is beneficialfor the production of polymer with high molecular weight byavoiding the side effect of branching and cross-linking whichcan be commonly encountered at high temperature [20ndash22]Meanwhile the photopolymerization is easy to operate andcontrol which requires only simple equipment economizedenergy sources making it an eco-friendly process [21] Inaddition photoinduced polymerization is believed to havethe ability to make surface modification on surface graftpolymerizations [23 24] However so far the most com-mon method to induce polymerization of AM and cationicmonomers is by heat There have been some reports on thesynthesis of P(AM-DAC) in aqueous solution induced byheat [25 26] but there are few reports currently on thesynthesis induced by UV light The existing studies about thepolymerization initiated by UV light are mostly concernedwith the microstructure and reaction kinetics of resultingcationic copolymers [27] and other similar polymerizationof P(AM-DAC) was carried out under the irradiation ofmetal halide lamps or low pressure mercury lamp [28 29]Considering the low efficiency of low pressure mercury lampand the high price ofmetal halide lampwe used high pressuremercury lamp to achieve high initiating efficiency and cost

saving Besides the report on flocculation performance of thepolymer induced by UV light is rarely mentioned thereforewe evaluated the sludge dewatering performance of thecopolymer induced byUV light compared with a commercialPAM

In this paper synthesis of the cationic polyacrylamideP(AM-DAC) was investigated using a novel initiation sys-tem photoirradiation 221015840-Azobis(2-amidinopropane) dihy-drochloride (V-50) was introduced into the system as thephotoinitiator for the polymerization of acrylamide withDAC as the cationic monomer in aqueous solutions Thephotoinitiator can initiate polymerization at low temperaturebecause the polymerizationwith photoinitiator does not haveany dependencies on reaction temperature Simultaneouslythe effects of the photoinitiators concentration monomersconcentration CO(NH

2)2(urea) concentration pH value

mass ratio of AM to DAC irradiation time on the molecularweight and dissolving time were investigated intensivelyStudy of the characterizations of the photoinitiated poly-mer P(AM-DAC) was realized by using such methods asFourier transform infrared spectra (FTIR) ultraviolet spectra(UV) and scanning electron microscope (SEM) Finallysludge dewatering experiment was carried out to evaluatethe dewatering efficiencies of the resulting polymers anda commercially available PAM Meanwhile the influencesof molecular weight and cationic monomer content of theresulting polymers on the sludge dewatering performancewere investigated

2 Experimental

21Materials ThemonomerAMwas industrialmaterial andused without further purification sourced from ChongqingLanjie Tap Water Company (Chongqing China) acryloy-loxyethyl trimethyl ammonium chloride (DAC) (80wt)was provided by Guangchuangjing Import and Export CoLtd Shanghai China EDTA (AR) and urea (AR) werepurchased from Chongqing Chuan-dong Chemical Co Ltd(Chongqing China) Photoinitiator 221015840-azobis(2-amidino-propane) dihydrochloride (V-50) was purchased from Rui-hong biological technology Co Ltd (Shanghai China)and other reagents were analytical grade used as receivedCommercial PAM was bought from Guanghui Chemical(Dalian China) (molecular weight provided by supplier was500 gsdotmolminus1 measured by our Lab was 460 gsdotmolminus1) Deion-ized water was used throughout this work High puritynitrogen was used in the synthesis of the polymer in orderto drive away the air existing in the reactor

22 Synthesis of the Copolymer P(AM-DAC) was synthe-sized from two monomers namely AM and DAC in anaqueous reaction system The reaction took place underUV irradiation and the specific procedure was shown stepby step as follows AM and DAC of varying dosages weredissolved in deionized water in the reaction vessel Themixture was stirred with a glass rod until the monomersdissolved completely Next a certain dosage of urea wasadded into the vessel The pH of the aqueous solution was


WaterWater

UV lamp


Reactor

N2N2






Mw = 10000 times [120578]

373

1066

(1)




FCMC =119872

119890minus119872

119889

119872

119890

times 100 (2)







H2C H2CCH

CHCH

CH

O C O O

O

O

C

C

NH2

O C NH2

CH2 CH2

CH2

CH2

CH2

CH2

CH3

CH3

CH3

CH3

CH3

N+

N+

Clminus

Clminus

UV

initiator


m n

H3C

P(AM-DAC)

+


80

60

40

20

Tran

smitt

ance

()

4000 3000 2000 1000


3462

2916

2864

1735

1633

1454 1348

1165

958

540



2groups in the


3and ndashCH

2asymmetry





Abso

rban

ce

180 200 220 240 260 280 300

Wavelength (nm)

AM

DAC

P(AM-DAC)











10

8

6

4

2

2 3 4 5 6 7 8

ln(A

)

ln(L)

n = 133

R2= 0954

ln(A) = 15911ln(L) minus 15897

(a)

10

8

6

4

2

2 3 4 5 6 7

ln(A

)

ln(L)

n = 137

R2= 0971

ln(A) = 16398ln(L) minus 16953

(b)



00 02 04 06 08 10400

500

600

700

800



40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104


15 20 25 30 35 40

150

300

450

600

750

900


40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104



20 40 60 80 100 12000

100

200

300

400

500

600

700



40

20

0

60

80

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104





00 01 02 03 04 05

550

600

650

700

750

800



Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min




3or



2)3] NTP NTP


400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9








Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


WaterWater

UV lamp


Reactor

N2N2






Mw = 10000 times [120578]

373

1066

(1)




FCMC =119872

119890minus119872

119889

119872

119890

times 100 (2)







H2C H2CCH

CHCH

CH

O C O O

O

O

C

C

NH2

O C NH2

CH2 CH2

CH2

CH2

CH2

CH2

CH3

CH3

CH3

CH3

CH3

N+

N+

Clminus

Clminus

UV

initiator


m n

H3C

P(AM-DAC)

+


80

60

40

20

Tran

smitt

ance

()

4000 3000 2000 1000


3462

2916

2864

1735

1633

1454 1348

1165

958

540



2groups in the


3and ndashCH

2asymmetry





Abso

rban

ce

180 200 220 240 260 280 300

Wavelength (nm)

AM

DAC

P(AM-DAC)











10

8

6

4

2

2 3 4 5 6 7 8

ln(A

)

ln(L)

n = 133

R2= 0954

ln(A) = 15911ln(L) minus 15897

(a)

10

8

6

4

2

2 3 4 5 6 7

ln(A

)

ln(L)

n = 137

R2= 0971

ln(A) = 16398ln(L) minus 16953

(b)



00 02 04 06 08 10400

500

600

700

800



40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104


15 20 25 30 35 40

150

300

450

600

750

900


40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104



20 40 60 80 100 12000

100

200

300

400

500

600

700



40

20

0

60

80

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104





00 01 02 03 04 05

550

600

650

700

750

800



Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min




3or



2)3] NTP NTP


400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9








Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


H2C H2CCH

CHCH

CH

O C O O

O

O

C

C

NH2

O C NH2

CH2 CH2

CH2

CH2

CH2

CH2

CH3

CH3

CH3

CH3

CH3

N+

N+

Clminus

Clminus

UV

initiator


m n

H3C

P(AM-DAC)

+


80

60

40

20

Tran

smitt

ance

()

4000 3000 2000 1000


3462

2916

2864

1735

1633

1454 1348

1165

958

540



2groups in the


3and ndashCH

2asymmetry





Abso

rban

ce

180 200 220 240 260 280 300

Wavelength (nm)

AM

DAC

P(AM-DAC)











10

8

6

4

2

2 3 4 5 6 7 8

ln(A

)

ln(L)

n = 133

R2= 0954

ln(A) = 15911ln(L) minus 15897

(a)

10

8

6

4

2

2 3 4 5 6 7

ln(A

)

ln(L)

n = 137

R2= 0971

ln(A) = 16398ln(L) minus 16953

(b)



00 02 04 06 08 10400

500

600

700

800



40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104


15 20 25 30 35 40

150

300

450

600

750

900


40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104



20 40 60 80 100 12000

100

200

300

400

500

600

700



40

20

0

60

80

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104





00 01 02 03 04 05

550

600

650

700

750

800



Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min




3or



2)3] NTP NTP


400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9








Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of









10

8

6

4

2

2 3 4 5 6 7 8

ln(A

)

ln(L)

n = 133

R2= 0954

ln(A) = 15911ln(L) minus 15897

(a)

10

8

6

4

2

2 3 4 5 6 7

ln(A

)

ln(L)

n = 137

R2= 0971

ln(A) = 16398ln(L) minus 16953

(b)



00 02 04 06 08 10400

500

600

700

800



40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104


15 20 25 30 35 40

150

300

450

600

750

900


40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104



20 40 60 80 100 12000

100

200

300

400

500

600

700



40

20

0

60

80

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104





00 01 02 03 04 05

550

600

650

700

750

800



Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min




3or



2)3] NTP NTP


400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9








Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


00 02 04 06 08 10400

500

600

700

800



40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104


15 20 25 30 35 40

150

300

450

600

750

900


40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104



20 40 60 80 100 12000

100

200

300

400

500

600

700



40

20

0

60

80

100

Diss

olvi

ng ti

me (

min

)

Mol

ecul

ar w

eigh

t

times104





00 01 02 03 04 05

550

600

650

700

750

800



Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min




3or



2)3] NTP NTP


400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9








Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


00 01 02 03 04 05

550

600

650

700

750

800



Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min




3or



2)3] NTP NTP


400

500

600

700

800

pH


Mol

ecul

ar w

eigh

t

times104

40

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)

3 4 5 6 7 8 9








Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





Zeta potentialmV



150

300

450

600

750

900


40

30

20

50

60

70

80

90

100

Diss

olvi

ng ti

me (

min

)


Mol

ecul

ar w

eigh

t

times104

8 2 7 3 6 4 5 5 4 6 3 7




100

95

90

85

80

75

70

65

6000 03 06 09 12 15 18

Filte

r cak

e moi

sture

cont

ent (

)


4

Mw = 400 times 104

Mw = 600 times 104







4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



4 Conclusions






Acknowledgments


References


























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of











































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

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