PAC composite and the adsorption of bisphenol A from aqueous solution

Journal of Saudi Chemical Society (2011) xxx, xxx–xxx

King Saud University

Journal of Saudi Chemical Society www.ksu.edu.sa www.sciencedirect.com

ORIGINAL ARTICLE

Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution Zhijian Li a, Mohammed Ashraf Gondal

b,*

, Zain Hasan Yamani

b

a

College of Food Science and Technology, Henan University of Technology, Zhengzhou 450052, China Laser Research Group, Physics Department and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, P.O. Box 5047, Dhahran 31261, Saudi Arabia

b

Received 5 May 2011; accepted 18 June 2011

KEYWORDS Bisphenol A (BPA); Adsorption; Removal; Powdered activated carbon (PAC); Cobalt ferrite

Abstract CoFe2O4/PAC composite adsorbent has been prepared via an immersing-calcination process, using ethylene diamine tetraacetic acid (EDTA) and citric acid (CIT) ligands containing sol as the CoFe2O4 precursor. The microstructure characterization and magnetic property of as-prepared sample were performed by means of XRD and VSM measurements. The adsorption kinetics, isotherms and thermodynamic process toward Bisphenol A molecules (BPA, which is considered as one of the typical endocrine disrupting chemicals) occurred on as-prepared magnetic adsorbent which were investigated by the pseudo-second order kinetic/intraparticle models, the Langmuir/ Freundlich adsorption isothermal models and basic chemical thermodynamics principles, respectively. ª 2011 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

1. Introduction Bisphenol A (BPA), a monomer of various polymeric materials, is widely used for the production of polycarbonate plastics * Corresponding author. Tel.: +966 38602351; fax: +966 38602293. E-mail address: [email protected] (M.A. Gondal). 1319-6103 ª 2011 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. Peer review under responsibility of King Saud University. doi:10.1016/j.jscs.2011.06.012

Production and hosting by Elsevier

and epoxy resins and also as stabilizer or antioxidant for many types of plastics such as polyvinyl chloride (Staples et al., 1998). However, BPA is also considered as a typical kind of endocrine disrupting chemicals (EDCs) which may influence the living system (Kang et al., 2006). Recently, various techniques have been put forward by researchers in order to remove BPA molecules from the environmental matrices, involving adsorption separation (Tsai et al., 2006; Dong et al., 2010), biochemical (Zhao et al., 2008), electrochemical (Kuramitz et al., 2001), sonochemical (Torres et al., 2007) and photochemical reactions (Huang and Huang, 2009), etc. Among the processes being proposed and/or developed, powdered-activated-carbon (PAC) based adsorption method is one of the most promising techniques owing to its low-cost, highly efficiency and less time consumption (Esteves et al., 2008; Mahmudov and Huang, 2010). However, the drawback

Please cite this article in press as: Li, Z. et al., Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution. Journal of Saudi Chemical Society (2011), doi:10.1016/j.jscs.2011.06.012

2

Z. Li et al.

Figure 1 Schematic illustration of CoFe2O4 precursor (sols) and basic formation process of the complex oxides (Note: the picture of CoFe2O4 crystal cell was copied directly from the website of http://wikis.lib.ncsu.edu/index.php/Image:Size21.png).

10

20

(511)

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(533)

(422)

(400) (222)

30

(440)

(311) (220)

All the commercial reagents were of analytical grade and used as received without further purification. The reagents and PAC were purchased from Sinopharm Group Chemical Reagent Co., Ltd. The excellent complexing ability toward metal ions was noticed and the roles as buffer reagents to keep the constant pH values of the solution, Citric acid (CIT) and ethylene diamine tetraacetic acid (EDTA) were used as ligands of Ferric and Cobalt ions, respectively. Cobalt and ferric were adopted as corresponding nitrate, namely, cobalt nitrate (Co(NO3)2Æ6H2O) and ferric nitrate (Fe(NO3)3Æ9H2O), respectively. Mole ratio of Co to Fe was 1:2. Co-EDTA and Fe-CIT complex solutions were prepared by mixing proper amount of cobalt nitrate, ferric nitrate and their corresponding ligands. The mole ratio of Co/EDTA and Fe/CIT was controlled at 1:1.5. After both of the pH of the solutions were adjusted by NH3ÆH2O/HNO3 to between 3 and 4, Co-EDTA and Fe-CIT solutions were then mixed with the Co/Fe mole ration of 1:2, and the pH of the final solution was adjusted between 3 and 4 by using NH3ÆH2O/HNO3. To obtain the CoFe2O4/PAC composite adsorbent, a certain amount of PAC was added into the complex compound

(111)

2. Materials and methods

solution above, ensuring the mass ration of PAC/CoFe2O4 was 10:1. The stable gels were prepared after stirring at 333 K for 5 h and then heated at 413 K in the oven for 48 h. The final product of PAC/CoFe2O4 composite was formed though a heating treatment process at 673 K under nitrogen atmosphere. Fig. 1 schematically illustrates the precursor of CoFe2O4 (sols) and the formation of complex oxides. The phase structure characterization of PAC/CoFe2O4 composite was carried out by X-ray diffraction (XRD) in the 2h range of 20–80 using Cu Ka X-ray source (k = 0.154, 18 nm) with voltage and current of 40 kV and 100 mA, respectively. The magnetic properties were measured by vibrating sample magnetometer (VSM, Lakeshore, Model 7300 series). To examine the behaviors of adsorption kinetic/isotherm and calculate the thermodynamics parameters, the adsorption experiments were carried out in 200 ml of 90 mg/L BPA solution at 150 rpm in a thermostatic shaker at 25 C for 24 h at pH 7.0 after 0.01 g amount of adsorbent was added unless otherwise indicated. The concentrations of BPA were determined at 276 nm, using a UV–vis spectrophotometer (VARIAN Cary 100) (Dong et al., 2010).

Intensity/ a.u.

regarding this technique is the separation of activated carbon which limits its further applications. Magnetic separation has been recognized as a quick and effective technique for separating magnetic particles with multi-composition. In recent years, the application of magnetic particle technology to solve environmental problems has received considerable attention (Tseng et al., 2007; Ao et al., 2008; Afkhami and Rasoul, 2009). In the present work, cobalt ferrite (CoFe2O4), a typical kind of multiple complex oxide with hard magnetic property (Sun et al., 2010) was induced into PAC through a sol-gel chemical route. Magnetic PAC was used for the adsorption of BPA from aqueous solutions and was then separated from the process following a simple magnetic process. The interfacial adsorption property of magnetic PAC for the removal of BPA was systematically investigated and the possible process and mechanism was discussed as well.

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2 Theta/ deg.

Figure 2

XRD pattern of as-prepared CoFe2O4/PAC adsorbent.

Please cite this article in press as: Li, Z. et al., Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution. Journal of Saudi Chemical Society (2011), doi:10.1016/j.jscs.2011.06.012

Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol 3. Results and discussion The XRD pattern of as-prepared CoFe2O4/PAC sample depicted in Fig. 2 suggested that all of the obvious diffraction peaks can be indexed to the cubic spinel structure (space group: Pn3m) of CoFe2O4 oxides (JCPDS card No. 5-667) with fine crystallinity, no characteristic peaks of impurities were detected in the corresponding XRD pattern and no apparent diffraction peak can be observed for the commercial PAC powders because of its amorphous structure. The hysteresis loop (as shown in Fig. 3) of as-prepared CoFe2O4/PAC adsorbent at room temperature was measured. The values of coercivity and saturation magnetization of the composite were

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2

estimated at 144.77 Oe and 6.2183 emu/g, respectively, which are lower than those of the pure phase of CoFe2O4 particles owning to the combination of small amount CoFe2O4 with PAC. The magnetic property of as-prepared CoFe2O4/PAC adsorbent indicates that such adsorbent can be easily separated from solution phase in several minutes through inducing an external magnetic field (inset of Fig. 3). The dependence of removal efficiency on the CoFe2O4/PAC adsorbent dosage was investigated, as depicted in Fig. 4, it was observed that the adsorption removal efficiency of BPA increased as increasing the CoFe2O4/PAC adsorbent dosage, and the removal efficiency can reach to 100% after 24 h adsorption process under the adopted dosage of 1 g/L. In addition, it can be clearly found that the increasing rates of removal efficiency became slower as increasing the dosage of as-prepared CoFe2O4/PAC adsorbent which was proportional to the adsorption sites, and the linear relationship between dosage and removal (%) became unapparent at the meantime. Such result is in agreement with those of carbon-nanotubes (CNTs) based adsorption processes where a decrease of adsorption removal efficiency can be observed generally if 350

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(a)

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-6 -6000

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-2000

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6000

qt (mg/g)

Moment/Mass (emu/g)

4

3

200 150 100

Field (Oe)

50

Figure 3 Representative M-H loop of the as-prepared magnetic CoFe2O4/PAC adsorbent. Inset: Optical-photographs of suspension of BPA and CoFe2O4/PAC adsorbent (a) and separation of the CoFe2O4/PAC adsorbent from water solution under an external magnetic field (b).

PAC CoFe2O4/PAC

0 0

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Time (min) 350

(b)

100 300 250

qt (mg/g)

Removal (%)

80

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40

200 150 100

PAC

50

20

CoFe 2O4/PAC 0 0

0 0.00

0.05

0.10

0.15

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Adsorbent dosage (g/200 mL) Figure 4 Dependence of removal efficiency (%) on the CoFe2O4/ PAC adsorbent dosage.

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15 1/2

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1/2

t (min )

Figure 5 The variations of adsorption capacity with adsorption time on PAC and CoFe2O4/PAC adsorbents (a) and the fitting results (b) through the intraparticle diffusion model.

Please cite this article in press as: Li, Z. et al., Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution. Journal of Saudi Chemical Society (2011), doi:10.1016/j.jscs.2011.06.012

4

Z. Li et al. Table 1 PAC.

Kinetic parameters of the pseudo second order and intraparticle diffusion models for BPA adsorption on PAC and CoFe2O4/

Adsorbents

Pseudo-second order kinetic model

PAC PAC/CoFe2O4

Table 2 298 K.

Intra-particle diffusion model

qe (mg/g)

k

r2

kp (mg/g min1/2)

C (mg/g)

r2

309.72 297.31

0.00279 0.00159

0.989 0.990

20.11 9.87

201.47 197.64

– 0.976

Parameters of the Langmuir and Freundlich adsorption models for BPA molecules on PAC and CoFe2O4/PAC adsorbents at

Adsorbents

Freundlich model K (mg1

PAC CoFe2O4/PAC

1/n

Langmuir model

L1/n g 1)

30.00 25.71

1/n

r2

qm (mg/g)

b (L/mg)

r2

0.572 0.604

0.980 0.972

771.2 727.2

0.0130 0.0113

0.961 0.942

the dosage of the adsorbent exceeded to a critical value (Wu, 2007; Gong et al., 2009). The employed dosage which exceeded to the critical value could possibly increase the viscosity of the solution, thus the diffusion of BPA molecules to the surface of CoFe2O4/PAC adsorbent would be inhibited. The dependence of BPA removal efficiency on contact time between adsorbent and adsorbate, which is depicted in Fig. 5(a), suggested that the adsorption-desorption equilibrium could be obtained after contact time of 120 min. To obtain the adsorption kinetic parameters of BPA molecules on CoFe2O4/ PAC, the pseudo-second order model was selected to fit the kinetic results (Ho and McKay, 2000). The corresponding fitting results shown in Table 1 demonstrated the good correlation coefficients (r2  0.99) for the pseudo-second order kinetic model by using CoFe2O4/PAC and PAC, implying the interaction of chemical adsorption could possibly have occurred during the adsorption process. On the other hand, it is worth noticing that only a small amount of adsorption-capacity decreased after CoFe2O4 loading, compared to the blank sample

of pure PAC adsorbent. It is reasonable to deduce that contribution of intraparticle diffusion was not the rate-controlling step for both adsorbents during the whole adsorption process, according to the fitting results by the intraparticle-diffusionmodel (Fig. 5(b), Table 1). The Langmuir and Freundlich isotherm models were selected to evaluate the adsorption capacity of adsorbents and understand the interactions between adsorbate and adsorbent (Langmuir, 1916; Freundlich, 1906). As given in Table 2 and Fig. 6, the adsorption isotherms of BPA molecules on both CoFe2O4/PAC and PAC can be fitted better by the Freundlich model than the Langmuir model, indicating the fact that the monolayer coverage adsorption process of BPA molecules on the adsorbents might not occur. Meanwhile, the Freundlich equation predicted that the BPA concentration on the adsorbent will increase as long as there was an increase in the BPA concentration in the liquid. And the fitting result by the Freundlich model revealed that the values of Freundlich exponents n (1.55 and 1.66) were greater that 1, representing the favorable adsorption condition (Annadurai et al., 2008).

450 400

289 K 298 K 308 K

450

PAC Freundlich PAC Langmuir CoFe2O4/PAC Freundlich

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400

CoFe2O4/PAC Langmuir

qe (mg/g)

qe (mg/g)

500

PAC CoFe2O4/PAC

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Ce(mg/L)

Figure 6 Adsorption isotherms of BPA on the PAC and CoFe2O4/PAC adsorbents and modeling using the Langmuir and Freundlich equations.

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Ce (mg/L)

Figure 7 Adsorption isotherms for BPA on CoFe2O4/PAC adsorbent at different temperatures.

Please cite this article in press as: Li, Z. et al., Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution. Journal of Saudi Chemical Society (2011), doi:10.1016/j.jscs.2011.06.012

Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol

5

Table 3 Parameters of the Langmuir and Freundlich adsorption models for BPA molecules on CoFe2O4/PAC adsorbents at 289, 298 and 308 K. T (K)

Freundlich model K (mg1

289 298 308

1/n

Langmuir model

L1/n g 1)

26.87 25.71 18.66

1/n

r2

qm (mg/g)

b (L/mg)

r2

0.601 0.604 0.644

0.954 0.972 0.939

792.3 771.2 756.1

0.0114 0.0112 0.0086

0.926 0.942 0.906

In order to initially study the thermodynamic process and parameters for the adsorption of BPA molecules on as-prepared CoFe2O4/PAC adsorbent, adsorption isotherms under different temperatures (289 K, 298 K and 308 K) were measured (as depicted in Fig. 7, and the results fitted by the Langmuir and Freundlich models are listed in Table 3. It was found easily that both K and qm value decreased irregularly with increasing temperature, implying the exothermic nature of BPA molecules adsorption on CoFe2O4/PAC adsorbent. Fig. 8 displays the plot of ln K vs. 1/T for thermodynamic parameters calculation for the adsorption of BPA molecules onto CoFe2O4/PAC adsorbent (Annadurai et al., 2008), and the chemical dynamic parameters were calculated by the result of linear fitting. As shown in Table 4, the negative of DG value ( 8.019, 7.841 and 7.642 kJ/mol at 289, 298 and 308 K, respectively) and positive DH value ( 13.75 kJ/mol) indicated that the adsorption of BPA molecules onto CoFe2O4/PAC adsorbent was a spontaneous and an exothermic process. The negative value of DS ( 19.83 J K 1 mol 1) obtained suggested the reversible nature during the adsorption process and possibly corresponded to a decrease in the degree of freedom of the species adsorbed (O¨zcan et al., 2006). The distance between two phenol hydroxyl radicals in a BPA molecular is 0.94 nm, approximately, which is less than the micropore diameter of PAC ( 2 nm), thus the surface area of adsorbent might be the major factor which can influence the adsorption capacity of BPA on CoFe2O4/PAC. The microporous surface can provide a mass of adsorption sites

3.5 3.4 3.3

lnK

3.2 3.1

lnK =1653.44/T-2.38543

3.0

Table 4 Thermodynamic parameters for the adsorption of BPA on CoFe2O4/PAC adsorbent. T (K)

K

289 298 308

26.872 25.701 18.660

DG (kg/mol) DH0 (kg/mol) DS (J/mol K) 8.019 7.841 7.642

13.75

19.83

thus leading to the strong physical effect with BPA molecules (Moreno et al., 1995). Noticing the rich p electronics in the PAC adsorbent, the p–p interaction (Coughlin and Ezra, 1968) cannot be ignored during the adsorption process of BPA molecules on as-prepared CoFe2O4/PAC adsorbent, though the donor-acceptor theory (Mattson et al., 1969) and hydrogen bond theory (Franz et al., 2000) were proposed to explain the adsorption mechanism of hydroxybenzene molecules on PAC materials as well. A recent study reported by Liu et al (Liu et al., 2009) showed that the chemical property of the PAC surface can greatly depend on the type of carbon source (such as wood/coal-based PAC) and heating treatment process (such as treated under different kinds of atmospheres), hence the surface chemical properties of asprepared CoFe2O4/PAC should be further investigated in order to deeply understand the adsorption process and mechanism and this work is ongoing. CoFe2O4/PAC adsorbent has been prepared via an immersing-calcination method. The as-prepared dispersed CoFe2O4/PAC adsorbent in the aqueous solution can be easily magnetic separated from the water phase after adsorption. The adsorption kinetics and isotherm results showed the similar adsorption capacity and the time-needed to obtain adsorption-desorption equilibrium with traditional PAC adsorbent. The thermodynamic process investigation indicated that the adsorption of BPA molecules onto CoFe2O4/PAC adsorbent was a spontaneous and an exothermic process.

2.9

Acknowledgments

2.8 2.7 3.20

3.25

3.30

3.35

1000/T K

3.40

3.45

3.50

-1

Figure 8 Plot of ln K vs. 1/T for thermodynamic parameters calculation for the adsorption of BPA molecules onto the CoFe2O4/PAC adsorbent.

This work was financially supported by Center of Excellence in Nanotechnology (CENT), KFUPM through the NSTIP program under Project #08-NAN93-4. We would like to thank Dr. Guangbin Ji, Mr. Haifu Deng, Ms. Xuanqi Liang and Mr. Syed Ahmed Ali Tirmizi for providing us valuable discussion, measurements and English revision/polish as well.

Please cite this article in press as: Li, Z. et al., Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution. Journal of Saudi Chemical Society (2011), doi:10.1016/j.jscs.2011.06.012

6 References Afkhami, A., Rasoul, N.A., 2009. Removal, preconcentration and determination of Mo(VI) from water and wastewater samples using maghemite nanoparticles. Colloids and Surfaces A: Physicochemical and Engineering Aspects 346, 52–57. Annadurai, G., Ling, L.Y., Lee, J.F., 2008. Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis. Journal of Hazardous Materials 152, 337–346. Ao, Y.H., Xu, J.J., Fu, D.G., Shen, X.W., Yuan, C.W., 2008. A novel magnetically separable composite photocatalyst: titania-coated magnetic activated carbon. Separation and Purification Technology 61, 436–441. Coughlin, R.W., Ezra, F.S., 1968. Role of surface acidity in the adsorption of organic pollutants on the surface of carbon. Environmental Science and Technology 2, 291–297. Dong, Y., Wu, D.Y., Chen, X.C., Lin, Y., 2010. Adsorption of bisphenol A from water by surfactant-modified zeolite. Journal of Colloid and Interface Science 348, 585–590. Esteves, I.A.A.C., Lopes, M.S.S., Nunes, P.M.C., Mota, J.P.B., 2008. Adsorption of natural gas and biogas components on activated carbon. Separation and Purification Technology 62, 281–296. Franz, M., Arafat, H.A., Pinto, N.G., 2000. Effect of chemical surface heterogeneity on the adsorption mechanism of dissolved aromatics on activated carbon. Carbon 38, 1807–1819. Freundlich, H.M.F., 1906. U¨ber die adorption in Isungen. Zeitschrift fur Physikalische Chemie-International 57, 385–470. Gong, J.L., Wang, B., Zeng, G.M., Yang, C.P., Niu, C.G., Niu, Q.Y., Zhou, W.J., Liang, Y., 2009. Removal of cationic dyes from aqueous solution using magnetic multi-wall carbon nanotube nanocomposite as adsorbent. Journal of Hazardous Materials 164, 1517–1522. Ho, Y.S., McKay, G., 2000. The kinetics of sorption of divalent metal ions onto sphagnum moss peat. Water Research 34, 735–742. Huang, Y.F., Huang, Y.H., 2009. Identification of produced powerful radicals involved in the mineralization of bisphenol A using a novel UV-Na2S2O8/H2O2-Fe(II,III) two-stage oxidation process. Journal of Hazardous Materials 162, 1211–1216. Kang, J.H., Kondo, F., Katayama, Y., 2006. Human exposure to bisphenol A. Toxicology 226, 79–89. Kuramitz, H., Nakata, Y., Kawasaki, M., Tanaka, S., 2001. Electrochemical oxidation of bisphenol A. Application to the removal of bisphenol A using a carbon fiber electrode. Chemosphere 45, 37– 43.

Z. Li et al. Langmuir, I., 1916. The constitution and fundamental properties of solids and liquids. Journal of the American Chemical Society 38, 2221–2295. Liu, G., Ma, J., Li, X., Qin, Q., 2009. Adsorption of bisphenol A from aqueous solution onto activated carbons with different modification treatments. Journal of Hazardous Materials 164, 1275–1280. Mahmudov, R., Huang, C.P., 2010. Perchlorate removal by activated carbon adsorption. Separation and Purification Technology 70, 329–337. Mattson, J.A., Mark Jr., HB., Malbin, M.D., Weber Jr., WJ., Crittenden, J.C., 1969. Surface chemistry of active carbon: specific adsorption of phenols. Journal of Colloid and Interface Science 31, 116–130. Moreno, C.C., Rivera, U.J., Lo´pez-Ramo´n, M.V., Marı´ n, A.F., 1995. Adsorption of some substituted phenols on activated carbons from a bituminous coal. Carbon 33, 845–851. O¨zcan, A., O¨ncu¨, E.M., O¨zcan, AS., 2006. Kinetics, isotherm and thermodynamic studies of adsorption of Acid Blue 193 from aqueous solutions onto natural sepiolite. Colloids and Surfaces A: Physicochemical and Engineering Aspects 277, 90–97. Staples, C.A., Dorn, P.B., Klecka, G.M., O’Block, S.T., Harris, L.R., 1998. A review of the environmental fate, effects, and exposures of bisphenol A. Chemosphere 36, 2149–2173. Sun, Y.Y., Ji, G.B., Zheng, M.B., Chang, X.F., Li, S.D., Zhang, Y., 2010. Synthesis and magnetic properties of crystalline mesoporous CoFe2O4 with large specific surface area. Journal of Materials Chemistry 20, 945–952. Torres, R.A., Abdelmalek, F., Combet, E., Pe´trier, C., Pulgarin, C., 2007. A comparative study of ultrasonic cavitation and Fenton’s reagent for bisphenol A degradation in deionised and natural waters. Journal of Hazardous Materials 146, 546–551. Tsai, W.T., Hsu, H.C., Su, T.Y., Lin, K.Y., Lin, C.M., 2006. Adsorption characteristics of bisphenol-A in aqueous solutions onto hydrophobic zeolite. Journal of Hazardous Materials 134, 169–175. Tseng, J.Y., Chang, C.Y., Chen, Y.H., Chang, C.F., Chiang, P.C., 2007. Synthesis of micro-size magnetic polymer adsorbent and its application for the removal of Cu(II) ion. Colloids and Surfaces A: Physicochemical and Engineering Aspects 295, 209–216. Wu, C.H., 2007. Adsorption of reactive dye onto carbon nanotubes: equilibrium, kinetics and thermodynamics. Journal of Hazardous Materials 144, 93–100. Zhao, J., Li, Y., Zhang, C., Zeng, Q., Zhou, Q., 2008. Sorption and degradation of bisphenol A by aerobic activated sludge. Journal of Hazardous Materials 155, 305–311.

Please cite this article in press as: Li, Z. et al., Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution. Journal of Saudi Chemical Society (2011), doi:10.1016/j.jscs.2011.06.012