poly(vinyl alcohol) composite gel for methylene blue removal

International Journal of Biological Macromolecules 81 (2015) 205–211

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International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac

Facile fabrication of magnetic carboxymethyl starch/poly(vinyl alcohol) composite gel for methylene blue removal Guisheng Gong a,b , Faai Zhang a,b,∗ , Zehong Cheng a,b , Li Zhou a,b,∗ a Guangxi Ministry-Province Jointly-Constructed Cultivation Base for State Key Laboratory of Processing for Nonferrous Metal and Featured Materials, Key Laboratory of New Processing Technology for Nonferrous Metal and Materials (Ministry of Education), Guilin University of Technology, Guilin 541004, PR China b College of Material Science and Engineering, Guilin University of Technology, Guilin 541004, PR China

a r t i c l e

i n f o

Article history: Received 9 June 2015 Received in revised form 22 July 2015 Accepted 29 July 2015 Available online 31 July 2015 Keywords: Magnetic composite gel Carboxymethyl starch Dye adsorption

a b s t r a c t This study presents a simple method to fabricate magnetic carboxymethyl starch/poly(vinyl alcohol) (mCMS/PVA) composite gel. The obtained mCMS/PVA was characterized by Fourier transform infrared (FTIR) spectra, vibrating-sample magnetometer (VSM) and scanning electron microscopy (SEM) measurements. The application of mCMS/PVA as an adsorbent for removal of cationic methylene blue (MB) dye from water was investigated. Benefiting from the combined merits of carboxymethyl starch and magnetic gel, the mCMS/PVA simultaneously exhibited excellent adsorption property toward MB and convenient magnetic separation capability. The effects of initial dye concentration, contact time, pH and ionic strength on the adsorption performance of mCMS/PVA adsorbent were investigated systematically. The adsorption process of mCMS/PVA for MB fitted pseudo-second-order model and Freundlich isotherm. Moreover, desorption experiments revealed that the mCMS/PVA adsorbent could be well regenerated in ethanol solution without obvious compromise of removal efficiency even after eight cycles of desorption/adsorption. Considering the facile fabrication process and robust adsorption performance, the mCMS/PVA composite gel has great potential as a low cost adsorbent for environmental decontamination. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Dye effluents discharged from various industrial fields such as textile, plastic, leather, dyestuff and paper-making have mutagenic and carcinogenic effects on the aquatic biota and human being because they are generally toxic and hard to degrade [1–3]. Therefore, it is of great importance to deal with the dye effluents. Various techniques such as biological treatment [4], advanced oxidation process [5], photocatalytic degradation [6] and adsorption [7–10] have been developed to remove dyes from water. Among them, adsorption technique is particularly attractive because of its simplicity of design, high efficiency and ease of operation [11]. In recent year, numerous attempts have been made to develop low cost and effective adsorbent. In this regard, increasing attention was paid on agricultural residues (e.g., rice husk [12] and wheat shell [13]) and natural polymers (e.g., chitosan [14,15] and cellulose [16,17]) because they are easy-available, renewable, and biodegradable.

∗ Corresponding authors at: College of Material Science and Engineering, Guilin University of Technology, Guilin 541004, PR China. E-mail addresses: [email protected] (F. Zhang), [email protected] (L. Zhou). http://dx.doi.org/10.1016/j.ijbiomac.2015.07.061 0141-8130/© 2015 Elsevier B.V. All rights reserved.

Starch, one of the most abundant renewable resources in the world has been investigated as an adsorbent to remove water pollutants [18–21]. For instance, Guo et al. [22] synthesized a crosslinked porous starch and found that its adsorption capacity of product for methylene blue (MB) can reach 9.46 mg g−1 , which was much higher than that of native starch. Mahmoud et al. [23] prepared a series of starch-based gels and used them to adsorb acid dye. Despite the progress on using starch as an adsorbent in recent years, the starch-based adsorbents generally suffer from several drawbacks such as low adsorption capacity [24], complex separation process and poor reusability [25]. Therefore, the practical applications of starch-based adsorbents for treatment of water pollutants are seriously restricted. Recently, magnetic adsorbents are emerging as a new generation of adsorbent for environmental cleanup because they can be readily separated from dye solution by an external magnetic field after adsorption [26–33]. Compared with other traditional separation techniques such as filtration and centrifugation, the magnetic separation process is easy to operate with high separation efficiency and low cost. Therefore, numerous natural polymer-based magnetic biosorbents (e.g., xylan [27], cellulose [28], chitosan [29], alginate [30,31]) have been explored for environmental decontamination. For example, Luo et al. [28] prepared

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G. Gong et al. / International Journal of Biological Macromolecules 81 (2015) 205–211 Table 1 Reaction conditions for magnetic mCMS/PVA composite gels.

Scheme 1. Synthetic route to the mCMS/PVA composite gel.

magnetic cellulose/activated carbon beads for adsorption of organic dyes from water. Cao and coworkers [29] fabricated magnetic Fe3 O4 /chitosan nanoparticles and investigated their adsorption behaviors toward reactive brilliant red X-3B. In this contribution, we present a facile one-step approach to prepare magnetic carboxymethyl starch sodium (CMS)/poly(vinyl alcohol) (PVA) (mCMS/PVA) composite gels based on the simultaneous formation of magnetic iron oxide nanoparticles and crosslinking of CMS and PVA (Scheme 1). Compared with the previous reports on starch-based adsorbents, the merits of this approach are as follows. First, the mCMS/PVA composite gels can not only show strong magnetic property associated with facile magnetic separation process but also can be readily fabricated in a large quantity, which is highly desired for practical applications [34]. Second, the utilization of CMS instead of native starch for preparing magnetic adsorbent can enhance the adsorption capacity significantly because the CMS contains abundant carboxylic groups [35]. The employment of mCMS/PVA composite gels as magnetic adsorbents to adsorb MB dye, one of the most widely used cationic dyes, from water was systematically investigated. 2. Materials and methods 2.1. Materials Carboxymethyl starch sodium (CMS, the degree of substitution is 0.35–0.5), poly(vinyl alcohol) (PVA, Mw = 195 kDa), iron(III) chloride hexahydrate (FeCl3 ·6H2 O) powder, iron(II) chloride tetrahydrate (FeCl2 ·4H2 O), ammonia solution (25 wt%), and methylene blue (MB, max = 662 nm) were purchased from Aladdin Chemistry Co. All other reagents were analytical grade and used as received without further purification. Deionized water was used throughout the experiments. 2.2. Characterization Fourier transform infrared (FTIR) spectra of the materials were carried out using Nicolet 205 spectrophotometer in the range of 400–4000 cm−1 (KBr disk). The magnetic moment was recorded at 300 K on a MPMS XL-7 vibrating-sample magnetometer (VSM). Scanning electron microscopy (SEM) images were obtained using JSM-6380 LV microscope. UV–vis spectra were recorded on a UV-3600 UV–vis spectrophotometer (Shimadzu). Transmission electron microscope (TEM) images were recorded on a JEOL-2010 TEM at 160 kV. TEM microtome specimens were cut using a diamond knife. The samples of 90–100 nm thickness were collected on hexagonal 400 mesh copper grids.

Sample

CPVA (mg mL−1 )

CCMS (mg mL−1 )

CFe(II) (mM)

CFe(III) (mM)

S1 S2 S3 S4

150 120 100 75

0 30 50 75

77.5 77.5 77.5 77.5

155 155 155 155

Table 1). In a typical procedure, PVA and CMS powder were dissolved in 30 mL of water at 95 ◦ C. After adding FeCl3 ·6H2 O and FeCl2 ·4H2 O (the molar ratio of FeCl3 ·6H2 O to FeCl2 ·4H2 O was kept as constant at 2:1), the mixture was stirred for 30 min at room temperature to form a homogeneous solution. Subsequently, ammonia solution (1.5 mL) was added and a black mCMS/PVA composite gel was gradually formed. After reaction for 24 h, the composite gel was transferred to a freezer with temperature of −15 ◦ C and maintained for 12 h and unfrozen at 25 ◦ C for 1 h. The above freezing–thawing process was repeated for three times. After freezing–thawing treatment, the solid was dried under vacuum for 24 h at 50 ◦ C to afford the final mCMS/PVA composite gel. The swelling ratio of mCMS/PVA gel was calculated as follows: swelling ratio =

(Ws − Wd ) × 100% Wd

(1)

where Wd and Ws are the weight of dried mCMS/PVA composite gel before and after immersing in water, respectively. 2.4. Dye adsorption The dye adsorption experiments were carried out in a batch system. Typically, 30 mg of mCMS/PVA adsorbent was added in 3 mL of dye solution of known concentration and the mixture was agitated at 25 ◦ C. The solution pH was adjusted with HCl (0.1 M) or NaOH (0.1 M). The ionic strength of solution was manipulated by adding NaCl. The dye solution sample was withdrawn at predetermined time interval until adsorption equilibrium was achieved. The adsorbent was separated from the dye solution by magnetic separation. To minimize random error, all adsorption experiments were carried out in triplicate. Dye concentration was determined by UV–vis spectrophotometer. Calibration curves were plotted between absorbance and concentration of the standard MB solution. The adsorption capacity was calculated from the following equation [36]: Qe =

(C0 − Ce )V m

(2)

where Qe (mg g−1 ) is the adsorption capacity of the adsorbent, C0 and Ce (mg L−1 ) are the initial and equilibrium concentrations of MB in the solution respectively, and V (L) is the volume of the MB solution, and m (g) represents the dose of the adsorbent. 2.5. Adsorbent regeneration Regeneration experiments were performed by immersing the dye-adsorbed sample S4 adsorbent into 20 mL of ethanol. After stirring for 1 h, the S4 adsorbent was separated by a magnet and then was reused for adsorption again. The ethanol solution was analyzed by UV–vis spectrophotometer. 3. Results and discussion

2.3. Synthesis of mCMS/PVA composite gels 3.1. Synthesis and characterization of mCMS/PVA composite gels To investigate the effect of reaction conditions on the properties of mCMS/PVA composite gels, a series of mCMS/PVA samples were prepared by adjusting the feed amounts of CMS and PVA (see

The synthetic route to the mCMS/PVA composite gel is illustrated in Scheme 1. As soon as the addition of ammonia solution, the

G. Gong et al. / International Journal of Biological Macromolecules 81 (2015) 205–211

207

Fig. 1. Photographs of magnetic CMS gel (a) and mCMS/PVA composite gel (b).

liquid mixture of CMS, PVA and iron salt with light yellow color was gelled immediately to form black mCMS/PVA composite gel. Since the synthetic process is easy to operate, it is possible to fabricate mCMS/PVA composite gel in a large quantity, which is crucial for practical applications. The synthetic protocol was designed based on the following considerations. On one hand, the CMS and PVA can adsorb iron ions by their hydroxyl groups in aqueous solution and subsequently act as stabilizer to control over the nucleation and growth of magnetic iron oxide nanoparticles. On the other hand,

the iron oxide nanoparticles can not only endow CMS and PVA with excellent magnetic characteristic but also serve as crosslinker to gelate the CMS and PVA. To investigate the effect of CMS content on the adsorption performance of mCMS/PVA composite gel, a series of mCMS/PVA samples were fabricated by adjusting the weight feed ratios of CMS to PVA (fwt ) from 0/1 to 1/1 (see Table 1). Because the magnetic CMS gel without PVA is very fragile, it is essential to introduce PVA to enhance the mechanical strength of the composite gel for the real applications. As presented in Fig. 1a, the low

Fig. 2. (a) FTIR spectra of CMS and mCMS/PVA composite gels. (b) Magnetization curve (at 300 K) of S4 composite gel. SEM images of S1 (c), S2 (d), and S4 (e) composite gels. (f) Representative TEM image of S4 sample.

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Swelling ratio (%)

500 400 300 200 S1 S2 S3 S4

100 0

0

200

400

600

800 1000 1200 1400

Time (min) Fig. 3. Swelling ratio of the mCMS/PVA composite gels.

stress and deformation lead to the breaking of magnetic CMS gel. On the contrast, the mCMS/PVA composite gel exhibited nice mechanical strength under press (Fig. 1b). Moreover, it can recover to its original shape quickly after releasing load. Fig. 2a shows the FTIR spectra of mCMS/PVA samples. As can be seen, the mCMS/PVA samples exhibit similar absorption characteristic to the CMS sample, suggesting the successful incorporation of CMS into magnetic composite gel. The strong absorption bands at 3403 cm−1 and 1103 cm−1 corresponding to OH groups, the peak at 1603 cm−1 corresponding to COO– groups, and the absorption bands at 926 cm−1 and 881 cm−1 assigned to cyclic ether groups can be clearly observed [37]. The magnetization curve reveals that the S4 sample is superparamagnetic at room temperature and its saturation magnetization value can reach 1.83 emu/g. The favorable magnetic property of mCMS/PVA promises the facile magnetic separation as shown in the inset of Fig. 2b. In order to gain more insight into the structural information of mCMS/PVA samples, the morphologies of S1, S3 and S4 after freezing–thawing treatment

were observed by scanning electron microscopy (SEM) as shown in Fig. 2c–e. The S1 sample (Fig. 2c) showed a relatively smooth surface with low surface porosity, whereas the S3 (Fig. 2d) and S4 (Fig. 2e) samples exhibited obvious porous structure with very coarse surfaces and many large-sized pores. This was attributed to the presence of CMS in S3 and S4 samples. The CMS could absorb a large amount of water as compared with PVA and the following squeeze of the adsorbed water by freezing–thawing treatment led to form numerous pores in mCMS/PVA. To determine the size of formed iron oxide nanoparticles in the mCMS/PVA, S4 was chosen as a representative sample for TEM measurement. Seen from the representative TEM image of S4 (Fig. 2f), iron oxide nanoparticles with size in the range of 5–10 nm are uniformly distributed in the gel matrix. In order to further probe the water absorption capability of the composite gels, the swelling behavior of S1, S2, S3 and S4 samples were examined as shown in Fig. 3. Obviously, the swelling ratio value increased with increasing the amount of CMS. In particularly, the S4 sample with the fwt value of 1/1 exhibited the swelling ratio of 435%, which was much higher than that of S1 sample (221%). The results can be explained by the fact that the hydrophilic CMS macromolecule contains numerous hydrophilic OH, COOH and cyclic ether groups to absorb water molecules as compared with PVA macromolecule, whose main chain is hydrophobic. 3.2. The adsorption performance of mPVA/CMS 3.2.1. Effect of CMS content on dye adsorption As the mPVA/CMS composite gel possesses strong magnetic property and abundant carboxylic groups, it is expected that the mPVA/CMS can be utilized as a magnetic adsorbent to remove cationic dyes from water. Methylene blue (MB), one of the most widely used dyes in printing and dyeing industry, was chosen as a representative cationic dye for the dye adsorption studies. The chemical structure of MB (Fig. 4a) has rich cationic atoms (e.g., N+ ),

Fig. 4. (a) Adsorption capacity of diverse mCMS/PVA composite gels for MB dye. The initial MB concentration is 320 mg L−1 . Inset of (a): photograph of MB solution (16 mg L−1 ) before and after adsorption on S4 sample. (b) Effect of contact time on the MB uptake by S4 sample. The initial MB concentration is 32 mg L−1 . Plots of pseudo-first-order (c) and pseudo-second-order (d) for adsorption of MB on S4 sample.

G. Gong et al. / International Journal of Biological Macromolecules 81 (2015) 205–211

pseudo-first-order equation : pseudo-second-order equation :

ln(Qe − Qt ) = ln Qe − k1t t = Qt



1 k2Qe 2



t + Qe

(3)

(a)

Qe (mg g-1)

80 60 40 20 0

0

200

11

3.2.3. Adsorption isotherms The adsorption isotherms are important data to understand the adsorption mechanism because the isotherm expresses the relationship between the amount of dye adsorbed by adsorbent and the concentrations of dye in the solution under equilibrium condition. They can provide information about adsorption mechanism, surface property and affinity of an adsorbent toward dye. The adsorption of MB with diverse initial MB concentrations was studied at pH 7 and room temperature (Fig. 5a). To determine the

600

800

(b)

10 9 r 2=0.008

8 7 6 5

0

200

400

600

800

Ce (mg L-1) 5

(c)

4

r 2=0.988

3

2

1

3

4

5

6

7

lnCe

(4)

where Qe and Qt are the amounts of dye MB adsorbed (mg g−1 ) at equilibrium and at time t (min), respectively, and k1 (min−1 ) is the pseudo-first-order rate constant, k2 (g mg−1 min) is the pseudosecond-order rate constant. The plots of ln(Qe − Qt ) versus t and t/Qt against t can be seen in Fig. 4c and d. The correlation coefficient (r2 ) value of the pseudo second-order model (0.987) is greater than that of the pseudo-first-order model (0.945), indicating that the pseudo-second-order model is more suitable for describing the adsorption process of MB on mPVA/CMS adsorbent. Since pseudosecond-order model is based on the assumption of chemisorption, this result implied that the adsorption of MB was due to chemisorption between mPVA/CMS adsorbent and MB [29].

400

Ce (mg L-1)

Ce/Qe (g L-1)

3.2.2. Adsorption kinetics As the adsorption rate is a crucial parameter for real dye removal application, the effect of contact time on the removal of MB by S4 adsorbent was evaluated with the initial MB concentration of 32 mg L−1 at room temperature and pH 7. As depicted in Fig. 4b, the adsorption amount of MB increased rapidly in the initial stage in first 120 min for all the adsorbents. As time passed, the adsorption rate slowed down until the adsorption process reached equilibrium in about 600 min. The beginning rapid step of adsorption is due to the existence of a large number of adsorption sites on the surface of S4 adsorbent. The subsequent slow adsorption is caused by the limited surface adsorption sites of S4 adsorbent and the repulsive forces between the solute MB molecules on the solid and liquid phase. The MB molecules gradually penetrated into the interior of S4 adsorbent and were slowly adsorbed by the internal adsorption sites. To further investigate the adsorption kinetics, the pseudofirst-order and pseudo-second-order kinetic models were used to analyze the experimental data. The two kinetic models are given in the following linear forms [38,39]:

100

lnQe

which are favorable for uptake by mPVA/CMS through electrostatic interaction. At relatively low initial concentration (16 mg L−1 ), the MB could almost be completely removed from water by S4 as presented in the inset of Fig. 4a. Moreover, the S4 adsorbent could be easily separated from water by a magnet. Since the adsorption capacity is considered as one of the most important parameters in adsorption application, the saturated adsorption capacities of mPVA/CMS sample with diverse contents of CMS were measured at high initial dye concentration (320 mg L−1 ) (Fig. 4a). Obviously, the introduction of CMS can remarkably enhance the adsorption capacity of mPVA/CMS. In particularly, the saturated adsorption capacity of S4 sample for MB dye can reach as high as 23.53 mg g−1 , which is much higher than that of S1 (5.40 mg g−1 ). The enhancement of adsorption capacity is ascribed to the presence of strong interactions such as electrostatic attraction between the CMS component and MB molecule. To further understand the adsorption process, the adsorption kinetics and isotherms were studied in detail by choosing S4 as a representative adsorbent.

209

Fig. 5. (a) Adsorption isotherms for the adsorption of MB on S4 sample at pH 7.0 and 25 ◦ C. (b) The linear dependence of Ce /Qe on Ce based on the Langmuir isotherm model. (c) The values of ln Qe against ln Ce based on the Freundlich isotherm model.

parameters associated with MB adsorption, the experimental data of the S4 adsorbent were modeled with the well known Freundlich and Langmuir isotherms [40–42]. The linear forms of the two isotherms are expressed as follows: Freundlich isotherm : Langmuir isotherm :

ln Qe = ln KF + b ln Ce Ce Ce 1 = + Qe Qm Qm KL

(5) (6)

where Ce is the equilibrium concentration of MB in the solution (mg L−1 ), Qe is the adsorption amount at the equilibrium (mg g−1 ), Qm is the maximum adsorption capacity (mg g−1 ), KF is the Freundlich constant, KL is the Langmuir adsorption constant, and b is a constant depicting the adsorption intensity. The Freundlich isotherm is the earliest known equation for describing adsorption mechanism. This fairly satisfactory empirical isotherm can be employed for non-ideal adsorption in a heterogeneous system. The Langmuir isotherm model is based on the assumption that the adsorption happened at a specific homogenous system, and all adsorption sites are equivalent and there are

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Removal efficiency (%)

Qe (mg g-1)

120

(a)

25

20

15

10

4

5

6

7

8

100 80 60 40 20 0

9

pH 24

(b)

1

2

3

4

5

Cycles

6

7

8

Fig. 7. Removal efficiency of S4 composite gel in eight successive cycles of desorption/adsorption as compared with the original adsorption capacity.

Qe (mg g-1)

20

efficiency reduced not more than 15% even after eight successive cycles of desorption/adsorption as compared with the original adsorption capacity. Thus, the S4 adsorbent possesses high reusability for treatment of MB dye. On the basis of the facile synthetic process, favorable adsorption capacity and high reusability of the S4 adsorbent, the mCMS/PVA composite gels hold great promises for the removal of dyes from wastewater [46].

16 12 8 4

0.0

0.1

0.2

0.3

0.4

0.5

NaCl (M)

Fig. 6. Effect of pH (a) and ionic strength (b) on the adsorption of MB dye by S4 sample. The initial MB concentration is 320 mg L−1 .

no interactions between adsorbates. The value of ln Qe against ln Ce according to the Freundlich isotherm and the value of Ce /Qe versus Ce according to the Langmuir isotherm are illustrated in Fig. 5b and c, respectively. The fitting results showed that the relative coefficient of the Freundlich model (0.988) was much higher than that of the Langmuir model (0.008), indicating that the uptake of MB by S4 adsorbent follows the Freundlich isotherm model but not the Langmuir model. In addition, this result also suggested the adsorbent surface was heterogeneous in nature [43]. 3.2.4. Effects of pH and ionic strength Since the solution pH can affect surface binding sites of the adsorbent, the influence of pH on the adsorption behavior of S4 adsorbent was evaluated within pH range 4–9 at room temperature, initial dye concentration of 320 mg L−1 and contact time of 12 h. Fig. 6a presents the adsorption capacities of S4 adsorbent for MB at different pH values. As can be seen, the adsorption capacities of S4 adsorbent for MB don’t show obvious changes with increasing pH from 4 to 9, implying that the adsorbent is suitable for dye adsorption over a wide range of pH. This result is possibly due to the fact that the variation of pH did not affect the surface binding sites of S4 [44]. In addition, the effect of ionic strength on the adsorption performance of S4 for MB was investigated. As shown in Fig. 6b, the adsorption capacities for MB decline obviously with increasing the concentration of NaCl. This was attributed to the suppression of the electrostatic interaction by the Na+ ions which competed with the dye molecules for the negatively charged binding sites on S4 surface [45]. 3.2.5. Regeneration studies An excellent adsorbent should not only exhibit nice adsorption capacity but also high reusability in order to reduce the overall cost of the adsorption. To investigate the reusability of S4 as adsorbent for MB removal, eight cycles of desorption/adsorption were carried out. The results in Fig. 7 indicated that the removal

4. Conclusions In summary, we have demonstrated an easy and viable strategy to fabrication of mCMS/PVA composite gel. The obtained mCMS/PVA with superparamagnetic property showed obviously enhanced adsorption capacity for cationic MB dye after incorporation of CMS. The adsorption kinetics and isotherms studies revealed that the adsorption process can be well fitted by the pseudosecond-order kinetic model and Freundlich isotherm model, respectively. The mCMS/PVA adsorbent exhibited high removal efficiency for MB over the pH range 4–9. The adsorption capacity of mCMS/PVA gradually declined with increasing the concentration of NaCl. Moreover, the mCMS/PVA adsorbent can be regenerated and utilized repeatedly. The results presented in this paper clearly highlight the combined advantages of CMS and magnetic gel, consequently offering an effective strategy to prepare robust adsorbent for environmental cleanup. Acknowledgements The authors greatly acknowledgement the financial support from the Natural Science Foundation of China (Nos. 21364003 and 51263004), Guangxi Natural Science Foundation (No. 2014GXNSFCA118004), and project of outstanding young teachers’ training in higher education institutions of Guangxi. References [1] V. Janaki, K. Vijayaraghavan, B.T. Oh, K.J. Lee, K. Muthuchelian, A.K. Ramasamy, S. Kamala-Kannan, Carbohydr. Polym. 90 (2012) 1437–1444. [2] C.A. Martinez-Huitle, E. Brillas, Appl. Catal. B: Environ. 87 (2009) 105–145. [3] E. Forgacs, T. Cserhati, G. Oros, Environ. Int. 30 (2004) 953–971. [4] J. Qian, H. Lu, Y. Cui, L. Wei, R. Liu, G.H. Chen, Water Res. 69 (2015) 295–306. [5] A. Asghar, A.A. Abdul Raman, W.M.A. Wan Daud, J. Clean. Prod. 87 (2015) 826–838. [6] P. Suresh, J.J. Vijaya, L.J. Kennedy, Mater. Sci. Semicon. Proc. 27 (2014) 482–493. [7] S. Sheshmani, A. Ashori, S. Hasanzadeh, Int. J. Biol. Macromol. 68 (2014) 218–224. [8] Z. Chen, L. Zhou, F. Zhang, C. Yu, Z. Wei, Appl. Surf. Sci. 258 (2012) 5291–5298. [9] V. Vadivelan, K.V. Kumar, J. Colloid. Interface Sci. 286 (2005) 90–100. [10] A.F. Hassan, A.M. Abdel-Mohsen, M.M.G. Fouda, Carbohydr. Polym. 102 (2014) 192–198. [11] Y. Bulut, H. Aydın, Desalination 194 (2006) 259–267.

G. Gong et al. / International Journal of Biological Macromolecules 81 (2015) 205–211 [12] A.N. Fernandes, C.A.P. Almeida, C.T.B. Menezes, N.A. Debacher, M.M.D. Sierra, J. Hazard. Mater. 144 (2007) 412–419. [13] S. Noonpui, P. Thiravetyan, W. Nakbanpote, S. Netpradit, Chem. Eng. J. 162 (2010) 503–508. [14] L. Wojnárovits, C.M. Földváry, E. Takács, Radiat. Phys. Chem. 79 (2010) 848–862. [15] H.Y. Zhu, Y.Q. Fu, R. Jiang, J. Yao, L. Xiao, G.M. Zeng, Bioresour. Technol. 105 (2012) 24–30. [16] R. Bhattacharyya, S.K. Ray, J. Ind. Eng. Chem. 20 (2014) 3714–3725. [17] K. Azzaoui, A. Lamhamdi, E.M. Mejdoubi, M. Berrabah, B. Hammouti, A. Elidrissi, M.M.G. Fouda, S.S. Al-Deyab, Carbohydr. Polym. 111 (2014) 41–46. [18] Y. Yang, X. Wei, P. Sun, J. Wan, Molecules 15 (2010) 2872–2885. [19] M.L. Zhai, F. Yoshii, T. Kume, K. Hashim, Carbohydr. Polym. 50 (2002) 295–303. [20] H. El-Hamshary, M.M.G. Fouda, M. Moydeen, S.S. Al-Deyab, Int. J. Biol. Macromol. 66 (2014) 289–294. [21] H. El-Hamshary, M.M.G. Fouda, M. Moydeen, M.H. El-Newehy, S.S. Al-Deyab, A. Abdel-Megeed, Int. J. Biol. Macromol. 72 (2015) 1466–1472. [22] L. Guo, G. Li, J. Liu, Y. Meng, Y. Tang, Carbohydr. Polym. 93 (2013) 374–379. [23] G.A. Mahmoud, S.E. Abdel-Aal, N.A. Badway, S.A.A. Farha, E.A. Alshafei, Starch-Starke 66 (2014) 400–408. [24] A. Olad, F.F. Azhar, M. Shargh, S. Jharfi, Polym. Eng. Sci. 54 (2014) 1595–1607. [25] F. Delval, G. Crini, S. Bertini, C. Filiatre, G. Torri, Carbohydr. Polym. 60 (2005) 67–75. [26] L. Zhou, B. He, J. Huang, ACS Appl. Mater. Interfaces 5 (2013) 8678–8685. [27] X.F. Sun, B. Liu, Z. Jing, H. Wang, Carbohydr. Polym. 118 (2015) 16–23. [28] X. Luo, L. Zhang, J. Hazard. Mater. 171 (2009) 340–347. [29] C. Cao, L. Xiao, C. Chen, X. Shi, Q. Cao, L. Gao, Powder Technol. 260 (2014) 90–97.

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[30] V. Rocher, J.M. Siaugue, V.C. Cabuil, A. Bee, Water Res. 42 (2008) 1290–1298. [31] V. Gopalakannan, N. Viswanathan, Int. J. Biol. Macromol. 72 (2015) 862–867. [32] Y. He, Z. Cheng, Y. Qin, B. Xu, L. Ning, L. Zhou, Mater. Lett. 151 (2015) 100–103. [33] Z. Cheng, J. Liao, B. He, F. Zhang, F. Zhang, X. Huang, L. Zhou, ACS Sustain. Chem. Eng. 3 (2015) 1677–1685. [34] P.R. Chang, P. Zheng, B. Liu, D.P. Anderson, J. Yu, X. Ma, J. Hazard. Mater. 186 (2011) 2144–2150. [35] X.Y. Chen, C. Chen, Z.J. Zhang, D.H. Xie, Powder Technol. 246 (2013) 201–209. [36] X.Y. Huang, H.T. Bu, G.B. Jiang, M.H. Zeng, Int. J. Biol. Macromol. 49 (2011) 643–651. [37] S.C. Pang, S.F. Chin, S.H. Tay, F.M. Tchong, Carbohydr. Polym. 84 (2011) 424–429. [38] J. Ma, Y. Jia, Y. Jing, Y. Yao, J. Sun, Dyes Pigment. 93 (2012) 1441–1446. [39] H.Y. Zhu, R. Jiang, L. Xiao, G.M. Zeng, Bioresour. Technol. 101 (2010) 5063–5069. [40] Y. Bulut, H. Karaer, J. Disper. Sci. Technol. 36 (2015) 61–67. [41] L. Zhou, J. Huang, B. He, F. Zhang, H. Li, Carbohydr. Polym. 101 (2014) 574–581. [42] S. Deng, R. Wang, H. Xu, X. Jiang, J. Yin, J. Mater. Chem. 22 (2012) 10055–10061. [43] R.R. Shan, L.G. Yan, K. Yang, S.J. Yu, Y.F. Hao, H.Q. Yu, B. Du, Chem. Eng. J. 252 (2014) 38–46. [44] L. Zhou, C. Gao, W. Xu, ACS Appl. Mater. Interfaces 2 (2010) 1483–1491. [45] Y. Hu, T. Guo, X. Ye, Q. Li, M. Guo, H. Liu, Z. Wu, Chem. Eng. J. 228 (2013) 392–397. [46] Y. Zhou, Y. Min, H. Qiao, Q. Huang, E. Wang, T. Ma, Int. J. Biol. Macromol. 74 (2015) 271–277.