93.mohsen ghorbania, hossein esfandian, nastaran taghipour, reza katal, 2010, application of...

Desalination 263 (2010) 279–284

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Desalination

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Application of polyaniline and polypyrrole composites for paper millwastewater treatment

Mohsen Ghorbani a, Hossein Esfandian b, Nastaran Taghipour c, Reza Katal c,⁎a Faculty of Chemical Engineering, Babol University of Technology, Babol, Iranb Faculty of Chemical Engineering, Elm-o-Sanat University, Tehran, Iranc Department of Chemical Engineering, Tarbiat Modares University, Tehran, Iran

⁎ Corresponding author. Fax: +98 2182883381.E-mail address: [email protected] (R. Katal).

0011-9164/$ – see front matter © 2010 Elsevier B.V. Aldoi:10.1016/j.desal.2010.06.072

a b s t r a c t
a r t i c l e i n f o
Article history:Received 3 May 2010Received in revised form 25 June 2010Accepted 28 June 2010

Keywords:PolypyrrolePolyanilinePaper mill wastewaterSawdustTreatmentComposite

This paper deals with a new application of polyaniline (PAn) and polypyrrole (PPy) synthesized chemically.Coated on sawdust via cast method the polypyrrole/sawdust (PPy/SD) and polyaniline/sawdust (PAn/SD) wereused as effective adsorbents for the removal of heavy metals, anions, color and COD (chemical oxygen demand)from mill paper wastewater. The products were investigated in terms of morphology and chemical structureusing scanning electron microscopy and Fourier-transform infrared spectroscopy (FTIR), respectively. It wasfound that PPy/SD and PAn/SD are very simple to prepare and can be used as effective adsorbents in the removalof anions, heavy metals, color and COD from paper mill wastewater.

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© 2010 Elsevier B.V. All rights reserved.

1. Introduction

High consumption of water is one of the most importantenvironmental concerns in paper industry. In an attempt to overcomethis problem, zero liquid effluent technologies are being developed.In these technologies circuits are closed and water is continuouslyrecycled [1–3]. Such wastewater contains a large amount of pollutantscharacterized by biochemical oxygen demand (BOD), chemical oxy-gen demand (COD), suspended solids (SS), toxicity, and colorantswhich cause bacterial and algal slime growths, thermal impacts,scum formation, color problems, and a loss of both biodiversity andaesthetic beauty in the environment [4]. The main treatment pro-cesses used at pulp and paper mill plants are primary clarification(sedimentation or flotation), secondary treatment (activated sludgeprocess or anaerobic digestion) and/or tertiary processes (membraneprocesses as ultrafiltration) [5]. Activated sludge plants have beenthe most common wastewater treatment process for the removal oforganics in our country; however, there are several problemswith theprocess. It produces sludges with very variable settlement properties,it is sensitive to shock loading and toxicity, and its capacity to removepoorly biodegradable toxic substances is limited [6]. Different type ofcatalysts such as Fenton agent and TiO2, have been used to degradepollutants from board paper industries and revealed that the Fenton

reagent gave a higher degree of total COD and BOD depletion com-pared to TiO2 [7]. In the same year, the flocculation performances ofpolyacrylamides have been reported for treating pulp and paper millwastewater. They revealed that cationic polyacrylamides, like Orga-nopol 5415, with a very highmolecular weight and low charge densityachieved a reduction of 95, 98 and 93 % in turbidity, total suspendedsolid (TSS) and total COD, respectively, with a sludge 1385–8947/$volume index (SVI) of 14 mL/g at the optimum dosage of 5 mg/l [8].Buzzini and coworkers reported a system based upon precipitationwith a microbial community which provided approximately 80–86%and 75–78% total COD removal with and without recirculation of theeffluent, respectively [9].

Since the discovery of conducting polymers three decades ago, alarge volume of research work has been performed associated withthe physics and chemistry of conducting polymers. PPy and PAn is themost environmentally stable known conducting polymer and also oneof the most commonly investigated conducting polymer due to itshigh electrical conductivity and simple preparation [10]. Conductingpolymers found applications in various fields such as microelectron-ics, composite materials, optics and biosensors [11] and as adsorbent[12,13]. The ion exchange capacities of conducting Polymers werewell understood and it was found to depend on the polymerizationconditions, the type and size of the dopants incorporated during thepolymerization process as well as on the ions present in the electro-lyte solution, the polymer thickness and ageing of the polymer [14].Review of the literature revealed that PPy synthesized in solutionswith small dopants such as Cl−, ClO4−, NO3−, etc., mainly exhibits

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Table 1Textile wastewater characterization.

Compound Concentration in waste water before removal

Mg (mg/l) 300S−2 (mg/l) 21SO4

−2 (mg/l) 155Fe (mg/l) 1.5Total N (NO3

−1, NO2−1) (mg/l) 33

Cu (mg/l) 0.5Color (adsorbance, at 600 nm) 0.3612COD (mg/l) 2700Zn (mg/l) 16

Fig. 1. SEM image of SD.

280 M. Ghorbani et al. / Desalination 263 (2010) 279–284

anion-exchanger behavior due to the high mobility of these ions inthe polymer matrix. While under certain conditions cation exchangewas also found to take place with large dopants like polyvinylsulfo-nate and polystyrenesulfonate, due to immobility of these ions in thepolymer matrix [14]. adsorption of metal ions by several functiona-lized polymers based on amines derivatives such as polyacrylonitrilefibers, ethylenediamine, polyacrylamides, poly-4-vinylpyridine, poly-ethyleneimine, aniline formaldehyde condensate, etc., have beenreported [15–20]. Chakraborty and coworkers have investigated oneamine-based polymer, short-chain PAn coated on jute fiber for theremoval of chromium in batch mode and Fixed-bed column [21,22] .polypyrrole was used in the removal of fluoride ions from aqueoussolution by conducting PPy [23].

This article reported the removal efficiency of heavy metal, anions,color and COD of paper mill wastewater using PAn/SD and PPy/SD.

2. Materials and methods

2.1. Instrumentation

A digital scale FR200, a PH meter, a scanning electron microscope(SEM) model XL30, a Fourier-transform infrared (FTIR) spectrometermodel shimadzu 4100 have been used in these experiments. Also amanual Photometer SQ300 Merck as spectrophotometer and MerckSpectroquant Test Kits were used for the analysis of COD (catologno.: 114555), NO2

− (no.: 100609), NO3− (no.: 100614), S−2 (no.: 1.14779),

SO4−2 (no.: 114548). Atomic absorption spectrometer (AAS) (Model 929,

Unicam) was used to analyze the concentration of heavy metal ions.Conductivity was measured by the four-point method using a currentsource.

Keithley 238, a scanner Keithley 706 with switching cards, anda Solartron-Schlumberger 7081 Precision Voltmeter. The densities ofthe sampleswere determined by the Archimedesmethod byweighingthe pellets in the air and immersed in decane.

2.2. Preparation of PAn/SD composite

1 g of KIO3 was added to 100 mL of sulfuric acid (1 M) and mixedby a magnetic stirrer to make a uniform solution. Then, 1 g of SD and1 mL fresh distilled aniline monomer was added to stirred solution.The reaction took place for 4 h at room temperature. Finally, theproduct was filtered to separate the impurities, and the productswere isolated on filter paper andwashed several times with deionizedwater and dried at room temperature.

2.3. Preparation of PPy/SD composite

5 g FeCl4 was added to 100 mL of water and then a uniform solu-tionwas resulted usingmagnetic mixer. Then, 1 g of SD and 1 mL freshdistilled pyrrole monomer was added to stirred solution. The reactionwas carried out for 4 h at room temperature. Finally, the product wasfiltered to separate the impurities, the products were isolated on filterpaper and washed several times with deionized water and dried atroom temperature.

In order to remove any dissolvable color materials in SD, PAn/SDand PPy/SD, they were washed with acetone and sodium hydroxide(0.3 M) until the washing liquid was colorless.

The composite has been grinded before use and their size werebetween 1 and 2 mm.

2.4. Removal technique

Adsorption experiments were performed by agitating 0.5 g of sor-bent with 50 mL of paper mill wastewater at 30±0.5 °C in magneticmixer. The rotating speed was 700 rpm throughout the study. At theend of predetermined time intervals, the sorbent was filtered and the

concentration of heavy metals, anions, color and COD was determined.All the tests were at least carried out twice. Standard deviation forduplicate experiments in all experiments was less than 3%. Table 1shows the characteristics of the wastewater (paper mill factory inShahi).

2.5. Characterization of mamrez tree sawdust

A SEM micrograph of mamrez tree sawdust is shown in Fig. 1.Mamrez tree sawdust is a heterogeneousmaterial consisting largely ofsmall spheres, irregular, porous, coke like particles of cell wall of plantcells. The surface seems to be rough, and protrusions can be seenthroughout the micrograph (Table 2). Pores can be seen however, notextending into the matrix. The surface roughness is indicative of highsurface area. Characteristics of the adsorbent such as surface area, bulkdensity, moisture content, ash content, solubility in water (inorganicand organic matter) were determined. The results are summarized inTable 3.

3. Results and discussion

The morphology of sawdust before and after coating with PAn andPPy is illustrated in Figs. 1–3. The coating with conducting polymerproduced by surface polymerization is very visible. The coating of SDhas always been found to be uniform by visual inspection, whilecoating defects have been suspected in the case of SD at low PAn orPPy contents. Some PAn precipitate produced by the precipitationpolymerization of aniline in the liquid phase adhered to the PAn-coated SD (Figs. 2 and 3) when the polymerization proceeded at ahigh (0.2 M) concentration of aniline. The macroscopic particles ofsawdust are not coated only at the surface but the big sizes of sawdustthat constitute their body have also been coated. This means that thereaction mixture diffuses into particles and all SD inside the particlesbecome coated with conducting polymer.

Table 2Various physical parameters for the adsorbent (mamrez tree sawdust).

Parameters Values

Particle size (mm) 3–5Surface area (m2/g) 620Bulk density (g/cm3) 1.25Moisture contents (%) 5.75Water soluble components (inorganic matter) (%) 16.45Insoluble components (organic matter) (%) 76.25

Table 3Conductivity and density of sawdust, conducting polymers, and their composites at20 °C.

Compound Conductivity (S cm−1) Density (g cm−3)

SD 1.4×10−14 1.25PAn/SD 0.30 1.30PPy/SD 0.16 1.34PAn 2.1 1.38PPy 0.9 1.45

Fig. 4. SEM image of PAn/SD with more zoom.

281M. Ghorbani et al. / Desalination 263 (2010) 279–284

Figs. 4 and 5, show with more Zoom Polymer coat is on thesawdust. As can be seen, PPy and PAn, has been formed. In general,increasing the amount of additives in the reaction, such as sawdust,influences the physical properties of composites.

Fig. 2. SEM image of PAn/SD.

Fig. 3. SEM image of PPy/SD.

Fig. 5. SEM image of PPy/SD with more zoom.

The structure of products was determined by FTIR spectrumwhichhas been done to identify the characteristics of the peaks of diagramfor the related products.

FTIR spectra in the 2500–500 cm−1 region, for the products areshown in Figs. 6 and 7. As can be seen, the peak 1502 cm-1 has beenassigned to the C=C stretching vibration of the quinoid ring, thepeak at 1402 cm−1 is assigned to the stretching vibration of C=C ofthe benzenoid ring and 1296 cm−1 correspondence to C–N stretchingvibration.

Fig. 6. FTIR spectra of PAn/SD.

image of Fig.�2

image of Fig.�3

image of Fig.�4

image of Fig.�5

image of Fig.�6

Fig. 7. FTIR spectra of PPy/SD.


For studying affects SD on conductive polymer properties, conduc-tivities and densities of composites, SD, PAn and PPy were measured(Table 3). PAn and PPy have identical densities therefore composites

Table 4Analyze of mill paper waste water after removal using PPy/SD in different time of reaction

Compound Removal efficiency after5 min of reaction (%)

Removal efficiency after10 min of reaction (%)

Mg (mg/l) 52.4 68.4S−2 (mg/l) 50.15 65.5SO4

−2 (mg/l) 55.35 70.64Fe (mg/l) 60.46 72.5Total N (NO3

−1, NO2−1) (mg/l) 56.65 67.14

Cu (mg/l) 60.11 71.5Color (adsorbance, at 600 nm) 62.55 74.58COD (mg/l) 38.72 52.47Zn (mg/l) 61.28 73.65

Table 5Analyze of mill paper waste water after removal using PAn/SD in different time of reaction

Compound Removal efficiency after5 min of reaction (%)


Mg (mg/l) 45.41 62.5S−2 (mg/l) 45.78 58.74SO4


−1, NO2−1) (mg/l) 44.85 62.34


Table 6Wastewater treatment using PPy/SD with different particle size.

Compound Particle size between10 and 15 μm

Particle1 and 2

Mg (mg/l) 81.75 84.5S−2 (mg/l) 79.25 83.67SO4


−1, NO2−1) (mg/l) 82.68 87.1


densities are equal. PA/SD, PPy/SD composites have much higher con-ductivities than conductivity of SD.

Experiments were done using PA/SD, PP/SD during 25 min with 5-minute intervals. As can be seen (Tables 4 and 5) increasing the time(5 to 20 min) removal efficiency increased but after 20 min it increasednot significantly.

For studying effect of SD size on removal efficiency, SD indifferentsizes (20–50 μm, 100–150 μm, 1–2 mm, 20–30 mm) was coated withpolymer and applied for wastewater treatment. Amount of adsorbentwas 0.5 g, wastewater volume was 50 mL and the treatment processwas in 20 min. The results are indicated in Tables 6 and 7. As can beseen decreasing SD size of 20–30 mm to 1–2 mm removal efficiencyincreased but decreasing more, removal efficiency decreased. Thereason could be for small size SD, polymer diffuses into SD so is notcoated on SD surface that made removal efficiency decreased.

In Table 8, the removal efficiency of wastewater is shown usingPAn, PPy and SD. As can be seen in Table 8, SD has low efficiency inthe removal of anions and COD, but its performance to remove metalsand color is considerable. PPy and PAn have noticeable efficiencyin the removal of metals, anions, color and COD. However, in allexperiments, the removal efficiency of PPy and PAn are lower thancomposites. Therefore it can be concluded that SD in the compositesdoes not play significant role in the anions and COD removal but the

.




78.54 84.5 84.8275.82 83.67 84.181.43 87.45 88.3285.27 94.2 94.5477.41 87.1 87.8584.72 92.17 92.2586.68 93.22 94.0561.44 65.41 65.5582.38 89.55 90.1

.




74.15 80.1 80.6572.51 81.3 82.0479.45 79.8 80.4280.34 85.6 86.473.68 82.7 83.8480.38 86.72 88.279.35 84.44 85.6553.25 58.71 59.3479.21 84.15 85.04

size betweenmm

Particle size between100 and 150 μm

Particle size between20 and 50 μm

72.3 61.9374.25 57.2574.84 55.4580.16 75.2370.64 53.2283.67 80.2483.45 75.3251.22 34.5480.86 76.78

image of Fig.�7

Table 7Wastewater treatment using PAn/SD with different particle size.

Compound Particle sizebetween 10and 15 μm

Particle sizebetween 1and 2mm

Particle sizebetween 100and 150 μm

Particle sizebetween 20and 50 μm

Mg (mg/l) 66.74 80.1 66.56 58.45S−2 (mg/l) 73.35 81.3 70.12 51.51SO4

−2 (mg/l) 77.21 79.8 68.23 50.46Fe (mg/l) 81.65 85.6 78.45 74.87Total N (NO3

−1, NO2−1) (mg/l) 76.72 82.7 63.75 48.53

Cu (mg/l) 82.68 86.72 81.25 77.86Color (adsorbance, at 600 nm) 79.78 84.44 80.56 72.37COD (mg/l) 50.45 58.71 45.75 30.25Zn (mg/l) 78.35 84.15 77.64 76.78

Table 8The analyze of wastewater after treatment using PAn, PPy and SD.

Compound Removalefficiencyof PAn (%)

Removalefficiencyof PPy (%)

Removalefficiencyof SD (%)

Mg (mg/l) 63.5 74.73 56.34S−2 (mg/l) 78.2 84.16 7.45SO4

−2 (mg/l) 72.27 85.24 11.24Fe (mg/l) 69.43 76.23 71.76Total N (NO3

−1, NO2−1) (mg/l) 81.7 84.11 9.8

Cu (mg/l) 72.54 72.45 78.41Color (adsorbance, at 600 nm) 57.41 61.37 71.12COD (mg/l) 57.45 64.52 3.07Zn (mg/l) 64.38 78.65 74.75

Table 9The removal efficiency of PAn, SD and PPy, SD (not in composite form).

Compound Removal efficiency(%) using PAnand SD (not in thecomposite form)

Removal efficiency(%) using PPy andSD (not in thecomposite form)

Mg (mg/l) 67.52 75.8S−2 (mg/l) 78.68 81.24SO4


−1, NO2−1) (mg/l) 79.3 83.25


Table 10Desorption data using H2SO4, NaOH and distillated water.

Compound DesorptionefficiencyusingNaOH (%)

DesorptionefficiencyusingH2SO4 (%)

Desorptionefficiency usingdistillatedwater (%)

Mg (mg/l) 32.5 85.52 51.35S−2 (mg/l) 93.74 18.14 38.74SO4

−2 (mg/l) 92.25 25.78 44.58Fe (mg/l) 24.27 88.2 42.5Total N (NO3

−1, NO2−1) (mg/l) 88.54 14.74 57.2

Cu (mg/l) 25.45 87.94 52.46Color (adsorbance, at 600 nm) 38.24 48.56 82.45COD (mg/l) 42.86 58.3 88.74Zn (mg/l) 92.5 47.8 61.5

283M. Ghorbani et al. / Desalination 263 (2010) 279–284

role of SD in the removal of themetals and color is considerable, and itcauses an increase in the removal efficiency of the composites.

Fig. 8 shows decolorization of papermill wastewater .As illustrated,the color of wastewater is decreased after treatment by composites,and clear liquid was obtained. This figure indicates the high efficiencyof PAn/SD and PPy/SD in the wastewater decolorization.

The results of application of PAn, SD and PPy, SD (not in the com-posite form) are shown in the Table 9. As can be seen, removal efficiencyof composites are higher thanPAn, SD and PPy, SD (not in the compositeform).

Heavy metals, color, COD and anions desorption from the PAn/SDand PPy/SD were investigated using solutions of the following threematerials: 1 M H2SO4, distillated water and 1 M NaOH. As can be seenin Table 10, anions desorption efficiencies using NaOH, wasmore thandesorption efficiencies using deionized water and H2SO4. Color andCOD desorption efficiencies using distilled water was more than twoothers. Metals (Fe, Mg and Cu) desorption efficiencies using H2SO4

was higher and for Zn desorption efficiency using NaOH was morethan others.

Fig. 8. (a) Wastewater, wastewater after treated with (b) PPy/SD, (c) PAn/SD″.

Removal efficiency of anions, color, COD and heavy metals usingregenerated adsorbents is shown in Table 11. The adsorbents werewashed by H2SO4, NaOH and deionized water respectively. As shownin Table 11, there is a little difference between regenerated and freshcomposites in the removal efficiency.

4. Conclusion

The composite of conducting polymer showed considerable poten-tial in the removal of heavy metals, color and anions from paper millwastewater and have the ability to remove COD; but the removalefficiency of COD is lower than removal efficiency of anions, metals andcolor. Composites regeneration operation is performed using NaOH,deionized water and H2SO4. After regeneration, composites were usedfor wastewater treatment. Ability of these composites has no consid-erable difference, with the fresh composites for removing color, COD,anions and heavy metals. Also, the efficiency of these composites arehigher than PAn PPy and SD to treat the wastewater.

Table 11Analyze of mill paper waste water before and after removal by regenerated PPy/SD andPAn/SD.

Compound Removal efficiencyof PAn/SD (%)

Removal efficiencyof PPy/SD (%)

Mg (mg/l) 77.85 82.71S−2 (mg/l) 79.01 83.22SO4


−1, NO2−1) (mg/l) 82.7 86.43


maity2all

Highlight

image of Fig.�8


Acknowledgements

The research upon which this paper is based was supported bya grant from the Khosro Katal. Saied Farhadi at Tarbiat ModaresUniversity is acknowledged for his assistance with experimental designand analysis.

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93.mohsen ghorbania, hossein esfandian, nastaran taghipour, reza katal, 2010, application of...

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