New crosslinked-chitosan graft poly(N-vinyl-2-pyrrolidone) for the removal of Cu(II) ions from aqueous solutions

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New crosslinked-chitosan graft poly(N-vinyl-2-pyrrolidone) for the removal of Cu(II) ions from aqueous solutions Zetty Azalea Sutirman a , Mohd Marsin Sanagi a,b,∗ , Juhanni Abd Karim a , Ahmedy Abu Naim a , Wan Aini Wan Ibrahim a,b a

Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM, Johor Bahru, Johor, Malaysia Centre for Sustainable Nanomaterials, IbnuSina Institute for Scientific and Industrial Research, UniversitiTeknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia b

a r t i c l e

i n f o

Article history: Received 9 February 2017 Received in revised form 20 August 2017 Accepted 17 September 2017 Available online xxx Keywords: Crosslinked-chitosan Graft copolymerization N -vinyl-2-pyrrolidone Free radical Adsorption

a b s t r a c t Crosslinked chitosan beads were grafted with N-vinyl-2-pyrrolidone (NVP) using ammonium persulfate (APS) as free radical initiator. Important variables on graft copolymerization such as temperature, reaction time, concentration of initiator and concentration of monomer were optimized. The results revealed optimum conditions for maximum grafting of NVP on 1 g crosslinked chitosan as follows: reaction temperature, 60 ◦ C; reaction time, 2 h and concentrations of APS and NVP of 2.63 × 10−1 M and 26.99 × 10−1 M, respectively. The modified chitosan beads were characterized by FTIR spectroscopy, 13 C NMR, SEM and BET to provide evidence of successful crosslinking and grafting reactions. The resulting material (cts(x)g-PNVP) was evaluated as adsorbent for the removal of Cu(II) ions from aqueous solutions in a batch experiment. The Langmuir and Freundlich adsorption models were also applied to describe the equilibrium isotherms. The results showed that the adsorption of the copper ions onto the beads agreed well with Langmuir model with the maximum capacity (qmax ) of 122 mg g−1 . © 2017 Elsevier B.V. All rights reserved.

1. Introduction Heavy metal contamination of various water bodies has increased a great concern among the public. Copper (Cu) is one the most widely used metal due to its technological importance and can be found in effluents especially from electrical and electroplating industries. Even though Cu is an essential trace element for all living organisms, it can cause harmful effects if exposed to high concentration [1]. In recent years, many works have been undertaken with the aim of finding alternative economic adsorbents for water treatment. This has led to the use of natural polymer based adsorbents such as starch, chitin, chitosan, alginate and cellulose because of their easily available and inexpensive [2]. Chitosan is one of the most abundant biopolymers in nature after cellulose, consisting mainly of ␤-(1,4) linked 2-deoxy2-amino-ɒ-glucopyranose units and partially of ␤-(1,4) linked 2-deoxy-2-acetamido-ɒ-glucopyranose. It naturally exists in the wall of fungi, exoskeletons of crustacean and insects. In fact,

∗ Corresponding author at: Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM, Johor Bahru, Johor, Malaysia. E-mail address: [email protected] (M.M. Sanagi).

chitosan can be deacetylated from chitin with a strong alkaline solution. Due to its biocompatibility, biodegradability, non-toxicity and adsorption properties, this biopolymer has been regarded as an excellent metal adsorbent by many researchers [3,4]. The presence of hydroxyl and amino groups in chitosan is highly advantageous to chelate with the metal ions. However, raw chitosan shows some shortcomings in terms of mechanical strength and solubility in acidic media which limits its performance in water treatment and purification [5,6]. Chemical modification through crosslinking on chitosan is found to be an effective way to improve its chemical stability in low pH solution. Numerous crosslinkers such as glutaraldehyde, epichlorohydrin, triphosphate and ethylene glycol diglycidylether have been widely reported for this purpose [7–9]. This treatment, somehow, reduces the adsorption capacity of chitosan since the amine groups of the polysaccharide are involved in the crosslinking reaction. Therefore, it is necessary to incorporate certain functional groups onto crosslinked chitosan to enhance the target metal sorption properties [10]. Graft copolymerization is a promising approach to impart desirable properties to a biopolymer. Grafting of chitosan with vinyl monomers are often carried out in the presence of free radical initiator. Generally, there are two types of free radical initiating systems; chemical (e.g. peroxoor azo compound) and irradiation

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(e.g. ␥-ray, microwave) [11]. For example, chitosan was successfully grafted with acrylamide in aqueous medium, using potassium persulfate as initiator [12]. Peroxydisulfate and ascorbic acid were used as redox initiator to graft methyl methacrylate onto chitosan [13]. Graft copolymerization of chitosan with ␧-caprolactone was performed under microwave irradiation [14] while crosslinked chitosan was grafted with itaconic acid using ammonium persulfate as initiator [15]. Crosslinked chitosan graft polyacrylonitrile copolymer was successfully prepared by combined techniques of ceric ammonium nitrate and UV radiation and the product was used for the removal of heavy metals [16]. In this work, raw chitosan was converted into beads and crosslinked with glutaraldehye. The beads were then grafted with N-vinyl-2-pyrrolidone using ammonium persulfate initiator. To the best of our knowledge this is the first report describing the grafting of NVP onto crosslinked chitosan beads via free radical polymerization. The graft copolymer (cts(x)-g-PNVP) showed acceptable capacity for the adsorption of Cu(II) ions from aqueous solutions. The experimental data were correlated with the Langmuir and Freundlich isotherm models. 2. Experimental 2.1. Material Chitosan with medium molecular weight (190,000–310,000 Da), glutaraldehyde, N-vinyl-2-pyrrolidone (NVP) and ammonium persulfate (APS) were purchased from Sigma-Aldrich Co. (St. Louis, USA). Methanol, acetic acid and hydrochloric acid were purchased from QRëc (Selangor, Malaysia). Sodium hydroxide (NaOH) pellet and standard solutions of cop® per, Cu(II) (Certipur ) were purchased from Merck (Darmstadt, Germany). All of the reagents were of analytical grade and used without further purification. 2.2. Preparation of chitosan beads Chitosan solution was obtained by dissolving 1 g of chitosan powder in 100 mL of acetic acid (1%, v/v). The solution was then added dropwise using a burette into NaOH solution (2 M) to induce the formation of chitosan gel beads. The solution was stirred overnight to neutralize the beads. The beads were intensively washed with distilled water to remove any remaining NaOH [17]. 2.3. Preparation of crosslinked chitosan beads Crosslinked chitosan beads were prepared using glutaraldehyde as crosslinker as previously described [18]. Freshly prepared wet chitosan beads were immersed in glutaradehyde solution (0.5%) to obtain a ratio of 1.5 mL of glutaraldehyde for 1 g of wet beads. The suspension was continuously stirred for 24 h at room temperature. Crosslinked chitosan beads were rinsed with distilled water several times to remove excess glutaraldehyde. 2.4. Grafting of crosslinked chitosan beads Dried crosslinked chitosan beads (1 g) and the required amount of APS in 10 mL distilled water were placed in a 250-mL threenecked flask equipped with a reflux condenser, a gas inlet system and nitrogen atmosphere. The mixture was stirred magnetically for 30 min to facilitate free radical formation on chitosan. A predetermined amount of monomer (NVP) was charged to the flask and the reaction was continued for a predetermined temperature. After a specified time, the grafted crosslinked beads were washed with a water-methanol mixture (1:5, v/v) to remove homopolymer of poly(N-vinyl-2-pyrrolidone) (PNVP). All samples were dried in an

oven at 60 ◦ C before being used for characterization. The grafting ratio G(%) and yield of graft copolymerization Y(%) were gravimetrically evaluated using the following equations [19]; G (%) =

W2 − W1 × 100 W1

(1)

Y (%) =

W2 − W1 × 100 W3

(2)

whereW1 , W2 and W3 represent weights of crosslinked chitosan beads, grafted copolymer and NVP monomer, respectively. 3.2. Characterization of the beads Fourier transform infrared spectroscopy (FTIR) of raw chitosan, glutaraldehyde crosslinked chitosan and grafted copolymer were performed on a Perkin Elmer SpectrumTM 400 model (USA) in the range of 4000–400 cm−1 . Solid-state 13 C NMR spectra were recorded using a Bruker Avance III HD spectrometer operating at 13 C resonance frequency of 100.6 MHz using a solid-state 13 C cross-polarization magic angle spinning (CP/MAS) with a 4-mm resonance probe head. The surface morphology of both chitosan and glutaraldehyde-crosslinked chitosan graft poly(Nvinyl-2-pyrrolidone) (cts(x)-g-PNVP) were examined using a JEOL JSM 6390LVSEM (Tokyo, Japan). BET specific surface areas of these materials were determined using a gas desorptioner/porosimetry (Micrometrics ASAP 2000). Meanwhile, energy dispersive X-Ray analysis (EDX) (Hitachi, TM3000) was conducted to evaluate the elemental compositions of the adsorbent before and after Cu(II) ion adsorption. 3.3. Sorption study Adsorption of Cu(II) ions onto cts(x)-g-PNVP was carried out by batch experiment. Standard stock solution of Cu(II) (1000 mg L−1 ) was diluted to give appropriate concentrations. 0.1 g of the modified chitosan beads were placed in a 50-mL Erlenmeyer flask containing 20 mL of Cu(II) solution. The mixture was agitated using an orbital shaker at 200 rpm at room temperature for 1 h. The effect of pH of the solution was investigated in the range of 2–6 by adding an appropriate amount of 0.1 M HCl or NaOH. The adsorption isotherm was studied using various concentrations of Cu(II) (200, 300, 400, 500 and 600 mg L−1 ) under optimum pH that has been determined in the previous step. The mixture was filtered and the residual metal concentration was measured using an atomic absorption spectrometer (Perkin-Elmer AAnalyst400). The percentage removal of Cu(II) ion (E) and adsorption capacity (q) were calculated according to the following equations [20]; Removal (%) = q=

(C0 − Ce ) × 100 C0

(C0 − Ce ) V m

(3) (4)

where C0 (mg L−1 ) and Ce (mg L−1 ) are the initial and final concentrations of the metal ion in solution respectively; V (L) is the volume of the solution and m (g) is the dry weight of modified chitosan beads used. 4. Results and discussion 4.1. Preparation and characterization of the beads A feasible mechanism of cts(x)-g-PNVP through crosslinking and graft reactions is proposed in Fig. 1. Chitosan was first crosslinked with glutaraldehyde to improve its chemical stability. This reaction was carried out by Schiff’s base mechanism in which one molecule

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Fig. 1. Proposed mechanism of crosslinking and graft copolymerization onto chitosan.

of glutaraldehyde reacted with two chitosan unities to form imine, C N groups [21]. The crosslinked chitosan was thereafter grafted with NVP using APS initiator. In free radical polymerization, it is common to use an initiator to facilitate the active site. APS is dissociated under a suitable temperature to give a pair of primary radicals, SO4 − .˙ These radicals abstracted hydrogen atom on chitosan backbone to produce corresponding macro-radicals and react with the NVP monomers which are in close vicinity of the reaction sites. The propagating chains are terminated by combination to form graft copolymer [22].

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4.1.1. FTIR The evidence of modifications (crosslinking and grafting) on chitosan is characterized based on functional groups using FTIR spectroscopy. Fig. 2 shows a FTIR spectrum for glutaraldehydecrosslinked chitosan and cts(x)-g-PNVP in comparison with that of raw chitosan. Spectrum for chitosan (Fig. 2a) has a broad peak at 3442 cm−1 due to O H and N H stretching vibrations of the saccharide structure. The 1649 cm−1 peak is attributed to the presence of acetamide group with C O stretching. The signals at 1424 and 1381 cm−1 corresponded to the C N bond stretching and deformation of C H, respectively [21]. In the glutaraldehydecrosslinked chitosan (Fig. 2b), the intensity of O H and N H groups at 3431 cm−1 is slightly reduced due to participation of primary amine of chitosan in crosslinking process with glutaraldehyde. A new band appearing at 1734 cm−1 can be attributed to C O stretching from aldehyde group as a resulted of self-polymerization of glutaraldehyde in aqueous solution [23]. The band at 1633 cm−1 represented the C N of imine group formed by amine of chitosan and carboxyl of glutaraldehyde through Schiff base reaction. The observed characteristic peaks of PNVP (Fig. 2c) in IR spectrum of the beads imply the presence of PNVP after grafting with crosslinked chitosan. IR spectrum of cts(x)-g-PNVP (Fig. 2d) showed a strong peak at 3437 cm−1 which can be ascribed to O H and N H stretching in the graft copolymer. A change in intensity at peak 1634 cm−1 for stretching of C O (amide I) indicated the presence of NVP on the beads. Furthermore, peaks at 1531 cm−1 , 1390 and 1293 cm−1 are observed due to characteristic of amide II, tertiary amine group and bending of C N, respectively [24]. 4.1.2. NMR The chemical structure of modified chitosan is also ascertained by its solid state 13 Carbon NMR (Fig. 3). In the spectrum for chitosan, peaks at ı 23 and ı 174 are attributed to methyl and carbonyl groups of N-acetylglucosamine unit, respectively. The other peaks in the ı 56–105 region were related to the distribution of anomeric carbons, carbons attached to amino group and other carbons of polysaccharide [25,26]. After modification of chitosan, the spectrum showed

Fig. 2. FTIR spectra of (a) chitosan; (b) glutaraldehyde-crosslinked chitosan; (c) PNVP and, (d) cts(x)-g-PNVP.

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Fig. 5. Effect of the temperature on the grafting parameters.

Fig. 3. Solid state

13

C NMR spectra for (a) chitosan and; (b) cts(x)-g-PNVP.

some major changes. It can be observed that additional peaks the region of ı 20–120 were due to the carbons of complex cts(x)g-PNVP. Small peak appeared at ı 43 represents the quaternary carbon (-CH CH2 CH-)n , the opening of vinyl group during the polymerization [27]. The line width of chitosan at ı 174 was also relatively enlarged due to introduction of carbonyl of NVP. 4.1.3. SEM Fig. 4 shows scanning electron micrographs for chitosan and cts(x)-g-PNVP at 1500 magnifications. The image of raw chitosan shows a smooth surface with no pores or semi-pores as it has a strong inter- and intra-hydrogen bonding [28]. However, introduction of glutaraldehyde and NVP on chitosan has significantly changed the morphology to spherulites-like structure. It might be due to the chemical interaction formed during the modifications of the surface of chitosan. 4.1.4. Surface area and porosity analysis The BET surface areas and pore structure parameters of chitosan and cts(x)-g-PNVP are shown in Table 1. The specific surface area for chitosan is 26.344 m2 /g and the pore size and pore volumes are 2.765 nm and 0.051 cm3 /g, respectively. After crosslinking and incorporation of NVP, the specific surface area of chitosan was slightly increased to 28.107 m2 /g. In a similar work, it was reported that glutaraldehyde crosslinked-epoxyaminated chitosan caused significant increase in the surface area of chitosan [29]. Furthermore, cts(x)-g-PNVP possesses a pore size 2.941 nm and pore

volume 0.029 cm3 /g. From the results obtained, it is clear that modification of chitosan has increased the surface area of ct(x)-g-PNVP, thus enhancing the adsorption of metal ions. 4.2. Optimization of graft copolymerization 4.2.1. Effect of reaction temperature The effect of reaction temperature on grafting copolymerization of crosslinked chitosan with PNVP was investigated in the range of 40–80 ◦ C, keeping other parameters constant at: [APS] = 21.91 × 10−1 M, [NVP] = 17.99 × 10−1 M, and time = 2 h. The results showed both G(%) and Y(%) increased continuously with the increase in temperature up to 60 ◦ C (Fig. 5). This can be associated to the increase in the production of primary free radicals at higher temperature and thereby enhancing the activity of graft copolymerization. The decrease in grafting parameters at temperatures of >60 ◦ C could be due to an early termination and chain transfer reaction [30]. The maximum percentages for grafting and yield obtained were 93.6% and 46.8%, respectively. 4.2.2. Effect of APS concentration Initiator concentration has a significance role on graft copolymerization. To investigate this, the APS concentration was varied from 0.88 − 4.38 × 10−1 M, while the other reaction variables were kept constant. The results are given in Fig. 6. As expected, increasing APS concentration would create more active sites on the chitosan backbone where grafting of NVP takes place and thus, accounting for higher grafting. The highest grafting (83.6%) and yield percentages (41.8%) were achieved at 2.63 × 10−1 M. However, beyond this concentration, the trend is inversed. This behavior is attributed to the probably interaction of excessive free radicals with either prop-

Fig. 4. Surface morphology of (a) chitosan and; (b) cts(x)-g-PNVP.

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Table 1 BET surface area and pore structure parameters of chitosan and cts(x)-g-PNVP. Adsorbents

BET surface area (m2 /g)

Pore diameter (nm)

Pore volume (cm3 /g)

chitosan cts(x)-g-PNVP

26.344 28.107

2.765 2.941

0.051 0.029

Fig. 6. Effect of the concentration of APS on the grafting parameters.

Fig. 7. Effect of the reaction time on the grafting parameters.

agating polymer or recombination with each other or both which led to termination [31]. 4.2.3. Effect of reaction time Fig. 4 summarizes the effects of reaction time on grafting parameters of cts(x)-g-PNVP. The study was carried out at different reaction times in the range of 60–360 min while keeping other conditions constant. Based on the results (Fig. 7), the grafting and yield percentages increased with polymerization time and reached their optimum values at 120 min. When the time was further extended, the trend was considerably leveled off due to a decrease in monomer and initiator concentrations as well as a reduction in the number of active sites on the macroradicals [32]. 4.2.4. Effect of NVP concentration Monomer concentration is another vital parameter on graft copolymerization. For that, 1 g of crosslinked chitosan was polymerized with different NVP concentrations using fixed concentration of APS (2.63 × 10−1 M) at 60 ◦ C for 2 h. It was found that grafting parameters increased steadily with the increase in NVP concentration and reached a maximum at 26.99 × 10−1 M (Fig. 8). It may be assigned to the increasing number of monomer molecules that diffused to the macroradicals sites and consequently led to a higher G(%) and Y(%). However, on further increase in NVP concentration, both percentages were found to decrease due to the domination of homopolymerization of PNVP which also in competi-

Fig. 8. Effect of the concentration of NVP on the grafting parameters.

Fig. 9. Percentage removal of Cu(II) at various pH ranges.

tion with grafting reaction [33]. The highest G(%) and Y(%) obtained were 138% and 46%, respectively. 4.3. Adsorption study 4.3.1. Effect of initial pH It is well known that the pH of a solution is an important factor affecting the amount of adsorption of heavy metal ions. The effect of initial pH on removal percentage of Cu(II) ions by cts(x)g-PNVP was studied over a pH range of pH 2–6. The optimum pH for the modified chitosan beads was found to be pH 5 with maximum percentage removal of 54.5% (Fig. 9). At acidic pH, the removal of Cu(II) ions was very low due to the presence of hydrogen ions which strongly compete with metal ions for adsorption sites [34]. In addition, the amine groups of the bead were prone to protonation and thus reducing the number of binding sites. At pH 6, Cu(II) ion tended to precipitate as an insoluble copper hydroxide, causing a decrease in the percent of the ion removal [35]. 4.3.2. EDX analysis EDX analysis was conducted to prove the adsorption of Cu(II) ions from aqueous solution onto cts(x)-g-PNVP. The spectra of the adsorbent before and after adsorption metal ions are shown in Fig. 10. Unlike spectrum for pristine adsorbent, the spectrum for adsorbent after adsorption of metal ions clearly showed the pres-

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Fig. 10. EDX spectra of (a) cts(x)-g-PNVP and (b) cts(x)-g-PNVP with adsorbed Cu(II) ion. Table 2 Langmuir and Freundlich constants for adsorption of Cu(II) onto Ch(GA)-g-PNVP. Langmuir

Freundlich −1

qmax (mg g 122

)

b (L mg 0.006

−1

)

R

Kf (mg(1–11/n). L1/n ) g−1

n

R2

0.958

2.321

1.594

0.957

2

ence of Cu peak with a weight distribution of 0.14%. This confirmed that Cu(II) ions were adsorbed on the beads. 4.3.3. Adsorption isotherm Equilibrium sorption of Cu(II) ion by the modified chitosan bead was carried out using different initial metal ion concentrations in the range of 30–2000 mg L−1 . The data was analyzed in terms of Langmuir and Freundlich models. Langmuir isotherm is one of the most frequent models used and it assumes that the adsorption process occurs on a homogenous surface by monolayer adsorption without any interaction between adsorbed ions [36]. The linearized equation of this model is represented as follows; Ce 1 Ce = + qe qmax qb

(5)

where q max is the maximum adsorption at monolayer (mg g−1 ), Ce is the equilibrium concentration of Cu(II) (mg L−1 ), qe is the amount of Cu(II) ion adsorbed per unit weight of the modified chitosan bead at equilibrium concentration (mg g−1 ) and b is the Langmuir constant related to the affinity of binding sites (L mg−1 ) and is a measure of the energy of adsorption. The plot of specific sorption, Ce /qe , against the equilibrium concentration, Ce is shown in Fig. 11a. The Freundlich equation is mainly used to describe the uptake of metal ionoccuringon a heterogeneous surface and its linearized form is as follows [37]; Logqe = LogKf + 1/nLogCe

(6)

where Kf is the Freundlich constant, n is the heterogeneity factor which is related to the capacity and intensity of the adsorption. Kf and n can be determined from a linear plot of log qe against log Ce (Fig. 11b). The regression equations, parameters as well as the correlation coefficients R2 for both isotherm models are summarized in Table 2. It can be seen that the experimental data fitted best with Langmuir model with higher value of correlation coefficient. Table 3 lists some reported Cu(II) ion adsorption capacity values for various chitosan based adsorbents. It shows that the maximum capacity of cts(x)-g-PNVP toward Cu(II) in this study is acceptable and comparable with the results of other adsorbents.

Fig. 11. Langmuir plot (a) and Freundlich plot (b) for the adsorption of Cu(II) ion onto cts(x)-g-PNVP.

Table 3 Comparison of Cu(II) ion adsorption capacities of heavy metal ions by different chitosan-based adsorbents. Adsorbent

Maximum adsorption capacity (mg g−1 )

References

Polyaniline graft chitosan beads Itaconic acid grafted crosslinked chitosan beads Chitosan crosslinked with ECH–TPP Carboxlated chitosan beads Chitosan/cellulose composite Glutaraldehyde crosslinked chitosan cts(x)-g-PNVP

100

[18]

19.6

[15]

130.7

[9]

86 53.3 59.7

[38] [39] [40]

122

This study

5. Conclusion Graft copolymer of crosslinked chitosan and NVP, in bead form, was successfully synthesized by free radical polymerization. Reaction conditions such as temperature, reaction time, concentrations of initiator and monomer have shown a great influence on grafting copolymerization. Maximum grafting (138%) and yield (46%) percentages were obtained at 60 ◦ C and a reaction time of 2 h, 2.63 × 10−1 M of APS and 26.99 × 10−1 M of NVP. FTIR, 13 C NMR, SEM and BETanalysis were used to elucidate the structure changes in comparison with chitosan. The bead was also used as adsorbent for Cu(II) ion removal from aqueous solution for the first time. The results suggested that this new modified chitosan could be workable as a potential sorbent material for removal of metal ion from aqueous solution.

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Acknowledgement The authors would like to thank Universiti Teknologi Malaysia and the Ministry of Higher Education Malaysia (MOHE) for facilitations and financial support through research grants number R.J130000.7826.4F631 and Q.J130000.2509.09H84 and studentship for Zetty Azalea Sutirman. References [1] Y.S. Ho, C.T. Huang, H.W. Huang, Equilibrium sorption isotherm for metal ions on tree fern, Process Biochem. 37 (2002) 1421–1430. [2] G. Crini, Recent developments in polysaccharide-based materials used as adsorbents in wastewater treatment, Prog. Polym. Sci. 30 (2005) 38–70. [3] S. Chauhan, Modification of chitosan for sorption of metal ions, J. Chem. Pharm. Res. 7 (2015) 49–55. [4] J. Wang, C. Chen, Chitosan-based biosorbents: modification and application for biosorption of heavy metals and radionuclides, Bioresour. Technol. 160 (2014) 129–141. [5] P. Alikutty, V.M.A. Mujeeb, M.A. Zubair, K. Muraleedhara, P.M. Rahman, Studies on the sorption capacity for Pb(II) and Hg(II) of citralidene chitosan, Polym. Bull. 71 (2014) 1919–1932. [6] C.J. Luk, J. Yip, C.M. Yuen, C. Kan, K. Lam, A comprehensive study on adsorption behaviour of direct, reactive and acid dyes on crosslinked and non-crosslinked chitosan beads, J. Fibre Bioeng. Inform. 1 (2014) 35–52. [7] R.S. Vieira, M.M. Beppu, Mercury ion recovery using natural and crosslinked chitosan membranes, Adsorpt 11 (2005) 731–736. [8] W.S. Wan Ngah, S.Ab. Ghani, A. Kamari, Adsorption behaviour of Fe(II) and Fe(III) ions in aqueous solution on chitosan and cross-linked chitosan beads, Bioresour. Technol. 96 (2005) 443–450. [9] R. Laus, V.T. Favere, Competitive adsorption of Cu(II) and Cd(II) ions by chitosan crosslinked with epichlorohydrin–triphosphate, Bioresour. Technol. 102 (2011) 8769–8776. [10] S. Benamer, M. Mahlous, D. Tahtat, A. Nacer-Khodja, M. Arabi, H. Lounici, N. Mameri, Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption, Radiat. Phys. Chem. 80 (2011) 1391–1397. [11] A. Bhattacharya, B.N. Misra, Grafting: a versatile means to modify polymers: techniques, factors and applications, Prog. Polym. Sci. 29 (2004) 767–814. [12] A.J.M. Al-Karawi, Z.H.J. Al-Qaisi, H.I. Abdullah, A.M. Al-Mokaram, D.T.A. Al-Heetimi, Synthesis, characterization of acrylamide grafted chitosan and its use in removal of copper(II) ions from water, Carbohydr. Polym. 83 (2011) 495–500. [13] V. Singh, A.K. Sharma, D.N. Tripathi, R. Sanghi, Poly(methylmethacrylate) grafted chitosan: an efficient adsorbent for anionic azo dyes, J. Hazard Mater. 161 (2009) 955–966. [14] C. Liu, R. Bai, Adsorptive removal of copper ions with highly porous chitosan/cellulose acetate blend hollow fiber membranes, J. Membr. Sci. 284 (2006) 313–322. [15] A. Bal, B. Ozkahraman, I. Acar, M. Ozyurek, G. Guclu, Study on adsorption, regeneration, and reuse of crosslinked chitosan graft copolymers for Cu(II) ion removal from aqueous solutions, Desalin, Water Treat. 52 (2013) 3246–3255. [16] P. Shankar, T. Gomathi, K. Vijayalakshmi, Adsorption of chromium (VI) from aqueous solution using crosslinked chitosan graft polyacrylonitrile copolymer, Indian J. Appl Res. 4 (2014) 62–65. [17] K.J. Adarsh, D.G. Madhu, A comparative study on metal adsorption properties of different forms of chitosan, Int. J. Innov. Res. Sci. Eng Technol. 3 (2014) 9609–9617. [18] E. Igberase, P. Osifo, A. Ofomaja, The adsorption of copper (II) ions by polyaniline graft chitosan beads from aqueous solution: equilibrium, kinetic and desorption studies, J. Environ. Chem. Eng. 2 (2014) 362–369. [19] K. Kaewtatip, V. Tanrattanakul, Preparation of cassava starch grafted with polystyrene by suspension polymerization, Carbohydr. Polym. 73 (2008) 647–655.

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[20] T.M. Elmorsi, Z.H. Mohamed, W. Shopak, A.M. Ismaiel, Kinetic and equilibrium isotherms studies of adsorption of Pb(II) from water onto natural adsorbent, J. Environ. Protect. 5 (2014) 1667–1681. [21] S.R. Acharyulu, T. Gomathi, P.N. Sudha, Synthesis and characterization of cross linked chitosan-polystyrene polymer blends, Pharma. Lett. 5 (2013) 74–83. [22] M. Constantin, I. Mihalcea, I. Oanea, V. Harabagiu, G. Fundueanu, Studies on graft copolymerization of 3-acrylamidopropyl trimethylammonium chloride on pullulan, Carbohydr. Polym. 84 (2011) 926–932. [23] O.A.C. Monteiro, C. Airoldi, Some studies of crosslinking chitosan-glutaraldehyde interaction in a homogeneous system, Int. J. Biol. Macromol. 26 (1999) 119–128. [24] M. Ahuja, S. Kumar, A. Kumar, Tamarind seed polysaccharide-g-poly(N-vinyl-2-pyrrolidone): Microwave-assisted synthesis, characterization, and evaluation as mucoadhesive polymer, Int. J. Polym. Mater. 62 (2013) 544–549. [25] L. Heux, J. Brugnerotto, J. Desbrieres, M.F. Versali, M. Rinaudo, Solid state NMR for determination of degree of acetylation of chitin and chitosan, Biomacromolecules 1 (2000) 746–751. [26] J. Liu, X.Y. Wen, J.F. Lu, J. Kan, C.H. Jin, Free radical mediated grafting of chitosan with caffeic and ferulic acids: structures and antioxidant activity, Int. J. Biol. Macromol. 65 (2014) 97–106. [27] K. Hatada, T. Kitayama, K. Ute, Determination of tacticity of polymethacrylamide by C-13 NMR spectroscopy, Polym. Bull. 9 (1983) 241–244. ´ [28] D. Stawski, S. Połowinski, Polymerization of itaconic acid, Polim 50 (2005) 118–122. [29] T.S. Anirudhan, S. Rijith, Glutaraldehyde cross-linked epoxyaminated chitosan as an adsorbent for the removal and recovery of copper(II) from aqueous media, Colloids Surf. A 351 (2009) 52–59. [30] A. Umar, A. Abu Naim, M.M. Sanagi, Synthesis and characterization of chitosan grafted with polystyrene using ammonium persulfate initiator, Mater. Lett. 124 (2014) 12–14. [31] V. Vijan, S. Kaity, S. Biswas, J. Isaac, A. Ghosh, Microwave assisted synthesis and characterization of acrylamide grafted gellan, application in drug delivery, Carbohydr. Polym. 90 (2012) 496–506. [32] S. Pandey, S.B. Mishra, Graft copolymerization of ethylacrylate onto xantham gum, using potassium peroxydisulfate as an initiator, Int. J. Biol. Macromol. 49 (2011) 527–535. [33] N. Isiklan, F. Kursun, Synthesis and characterization of graft copolymer of sodium alginate and poly(itaconic acid) by the redox system, Polym. Bull. 70 (2013) 1065–1084. [34] N.V. Suc, H.T.Y. Ly, Lead(II) removal from aqueous solution by chitosan flake modified with citric acid via crosslinking with glutaraldehyde, J. Chem. Technol. Biotechnol. 88 (2013) 1641–1649. [35] N. Tirtom, A. Dincer, S. Becerik, T. Aydemir, A. Celik, Removal of lead(II) ions from aqueous solution by using crosslinked chitosan-clay beads chitosan-clay beads, Desalin. Water Treat. 3994 (2012) 37–41. [36] S.A. Akolo, A.S. Kovo, Comparative study of adsorption of copper ion onto locally developed and commercial chitosan, J. Encapsulat. Adsorpt. Sci. 5 (2015) 21–37. [37] A.H. Gedam, R.S. Dongre, Adsorption characterization of Pb(II) ions onto iodate doped chitosan composite: equilibrium and kinetic studies, RSC Adv. 5 (2015) 54188–54201. [38] M. Rajiv, G.N. Kousalya, N. Viswanathan, S. Meenakshi, Sorption behaviour of copper on chemically modified chitosan beads from aqueous solution, Carbohydr. Polym. 83 (2011) 1082–1087. [39] C. Liu, R. Bai, Adsorptive removal of copper ions with highly porous chitosan/cellulose acetate blend hollow fiber membranes, J. Membr. Sci. 284 (2006) 13–322. [40] W.S. Wan Ngah, C.S. Endud, R. Mayanar, Removal of copper(II) ions from aqueous solution onto chitosan and cross-linked chitosan beads, React. Funct. Polym. 50 (2002) 181–190.

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