Adsorption properties of crosslinking carboxymethyl cellulose grafting dimethyldiallylammonium chloride for cationic and anionic dyes

Carbohydrate Polymers 151 (2016) 283–294

Contents lists available at ScienceDirect

Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol

Adsorption properties of crosslinking carboxymethyl cellulose grafting dimethyldiallylammonium chloride for cationic and anionic dyes Qingwen Lin, Mengfan Gao, Jiali Chang, Hongzhu Ma ∗ School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, Shaanxi 710119, People’s Republic of China

a r t i c l e

i n f o

Article history: Received 16 April 2016 Received in revised form 16 May 2016 Accepted 18 May 2016 Available online 20 May 2016 Keywords: Carboxymethyl cellulose Dimethyldiallylammonium chloride pH-sensitive Selective adsorption Dyes

a b s t r a c t Novel and efficient microspheres adsorbent (MCA-E0.7 /CMC-g- PDMDAAC), based on monochloroacetic acid (MCA) modified epichlorohydrin (ECH) cross-linked carboxymethyl cellulose (CMC), then grafting by dimethyldiallylammonium chloride (DMDAAC), was synthesized and its adsorption properties on cationic and anionic dyes were investigated. The results demonstrated that such MCA-E0.7 /CMC-gPDMDAAC microspheres showed pH-sensitive and could effectively adsorb cationic dye methylene blue (MB) or anionic dye orange II (OR II), at near neutral (pH > 4) or acidic (pH < 3) condition, respectively. Moreover, it could selectively adsorb the cationic dye MB from the cationic/anionic dye mixture at neutral pH condition. The desorption experiments were mainly performed under acidic (pH 3) or basic (pH 11) condition, over 98.54% of MB and 83.07% of OR II can be desorbed within 20 min, respectively. The pseudosecond-order kinetic model and Langmuir isotherm provide better correlation with the experimental data for the adsorption of dyes onto MCA-E0.7 /CMC-g-PDMDAAC microspheres. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction In modern time, as various industries growing fast and fast, energy crisis and environment pollution problem have gradually caught the attention of the people. Printing and dyeing wastewater was one of the industrial pollutant headstreams. Most of these dyes contain aromatic structures and azo groups (Fan, Liu, Zhang, & Chen, 2015), which are toxic and hard-degraded (Bulut & Karaer, 2015; Hameed, Din, & Ahmad, 2007; Yan et al., 2011). The plant effluent containing these dyes released into the wastewater stream would cause adverse effects on ecological equilibrium and human health if discharged without any treatment (Chung, 2000). Therefore, it is necessary to find appropriate treatment strategies for efficient removal of dyes from wastewater system before discharge. Currently, several methods for dye removal in wastewater treatment are undertaken such as adsorption, oxidation, ozonation, electrocoagulation and membrane separation (Chan, Wu, Juan, & Teh, 2011; Gadd, 2009; Liu, Ma, & Zang, 2013; Martínez-Huitle & Brillas, 2009; Teh & Mohamed, 2011). Among them, adsorption is gaining popularity due to its easy-operation, low cost, recyclable and high-efficiency in dealing with various pollutants (Rafatullah,

∗ Corresponding author. E-mail address: [email protected] (H. Ma). http://dx.doi.org/10.1016/j.carbpol.2016.05.064 0144-8617/© 2016 Elsevier Ltd. All rights reserved.

Sulaiman, Hashim, & Ahmad, 2010; Zhang et al., 2015). This has encouraged the exploration of adsorbents with abundant availability and good economy. Nowadays, many kinds of adsorption materials are investigated, such as fly ash (Gao et al., 2015), activated carbon (Girods et al., 2009), tea waste ash and rice husk (Mittal, Mittal, Malviya, Kaur, & Gupta, 2010), and so on. However, the use of adsorption materials with the ability of pH-sensitive or selective adsorption for certain dyes are scarce, there is still a great need to explore some kinds of new and low cost adsorbents with high adsorption ability, even high selectivity and pH-sensitive towards specific dyes (Fu et al., 2016; Liu et al., 2016). With the expansion of population and development of world economy, it makes the demand for various natural resources day by day. Compared with other materials, cellulose is considered as an almost inexhaustible source of raw material for the increasing demand for environmentally friendly and biocompatible products (Algarra et al., 2014; Amin, Ahmad, Halib, & Ahmad, 2012). Similarly, carboxymethyl cellulose (CMC) are very important derivatives of cellulose, which has gained increasing interest in the recent years, due to its good solubility, low-cost, non-toxic, modifiable and biodegradable. Moreover, the hydroxyl and carboxyl groups of CMC can be transformed into various functional groups. Therefore, CMC is considered as a biocompatible material used in drug delivery or an effective adsorbent for the metal ions and syn-

284

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

thetic dyes (Deng et al., 2012; Salama, Shukry, & El-Sakhawy, 2015; Zhang et al., 2014). This work aims to prepare a novel effective adsorbent, MCAE0.7 /CMC-g-PDMDAAC, based on monochloroacetic acid (MCA) modified epichlorohydrin (ECH) cross-linked CMC by grafting of dimethyldiallylammonium chloride (DMDAAC), which shows pH-sensitive towards cationic dye and anionic dye from aqueous solutions. Moreover, the selective adsorption properties of adsorbent MCA-E0.7 /CMC-g-PDMDAAC towards cationic dye of methylene blue (MB) from the binary mixture of cationic and anionic dyes were also studies. The influence factors, containing contact time, solution pH, and initial dye concentration, were systematically studied. In addition, batch adsorption experiments were carried out with kinetic and adsorption isotherm to investigate its adsorption property. 2. Experimental

2015). The product was washed with ethanol and water successively until the unreacted substances were completely removed, then freeze-dried at −50 ◦ C for further use, coded as MCA-E0.7 /CMCg- PDMDAAC. 2.5. Characterization of the microspheres All the CMC microspheres were visualized by using polarizing microscope (LEICA-DMLP, EC600, Leica, Linkam) and scanning electron microscopy (SEM, Quanta 200, FEI). The specific surface areas of the microspheres were measured by Bruner–Emmet–Teller (BET, ASAP2020 Mike, USA) method. Fourier-transform infrared (FTIR) spectra of the microspheres were undertaken from 400 to 4000 cm−1 on an FTIR spectrometer (Tensor 27, BRUKER, Germany). The zeta potential of the samples was determined using laser particle-Zeta potential recorder (Delsa Nano C, Beckman Coulter). A certain amount of the microspheres were dispersed in distilled water with various pH values before this measurement.

2.1. Materials Carboxymethyl cellulose sodium (CMCNa, viscosity: 300–800 mPa s, C.P.), epichlorohydrin (ECH, A.R.), span 80 (A.R.), liquid paraffin (C.P.), urea (A.R.), sodium hydroxide (NaOH, A.R.), monochloroacetic acid (MCA, A.R.), butyl alcohol (C4 H9 OH, A.R.), carbon tetrachloride (CCl4 , A.R.), diallyldimethylammonium chloride solution (DMDAAC, 60%) potassium peroxydisulfate (K2 S2 O8 , A.R.), methylene blue (MB, C16 H18 ClN3 S), orange II (OR II, C16 H11 N2 O4 SNa·5H2 O), and methyl orange (MO, C14 H14 N3 NaO3 S) were obtained from Sinopharm Chemical Reagent Co., Ltd., and used without further purification. 2.2. The crosslinking of carboxymethyl cellulose by ECH (E0.7 /CMC) The E0.7 /CMC microspheres were synthesized by an inverse suspension crosslinking technique with ECH as the crosslinking agent. 0.63 g CMCNa was dissolved in 7.0 mass% NaOH and 12.0 mass% urea aqueous solution (12.5 mL) with stirring until CMCNa dissolving completely, then 50 mL liquid paraffin, in which 0.2 g span 80 as surfactant and 0.7 mL butyl alcohol as co-surfactant (Zhang, Han, Li, & Liu, 2013) were dissolved, were dispersed into the mixture. Meanwhile, in order to improve the suspension of particles and increase the stability of system, 0.7 mL CCl4 was added with stirring. Finally, as the crosslinking agent, 2.5 mL ECH were introduced with a stirring speed of 720 rpm for 10 h at room temperature. The obtained products were washed with ethanol and distilled water several times, respectively, and collected by suction filtration for further use. 2.3. Synthesis of MCA-E0.7 /CMC microspheres 20.0 g wet E0.7 /CMC microspheres were added to NaOH (5.0 mass%) aqueous solution (30 mL) in a 100 mL beaker. In order to introduce more anionic carboxyl groups on E0.7 /CMC, 2.40 g MCA was added with a stirring speed of 350 rpm for 2 h at 65 ◦ C. Then, the obtained products were washed with distilled water for several times and collected by suction filtration for further use. The product was coded as MCA-E0.7 /CMC. 2.4. Grafting DMDAAC to MCA-E0.7 /CMC microspheres 20.0 g wet MCA-E0.7 /CMC microspheres were added to 20 mL distilled water in a reactor. Then the initiator, K2 S2 O8 (0.1 g) followed by the graft cationic monomer DMDAAC (1 mL) was added to the reaction mixture with a stirring speed of 350 rpm in a water bath at 50 ◦ C for 3 h (Chen, Liu, Tang, & Tan, 2010; Salama et al.,

2.6. Adsorption behavior 10 mg of microspheres were immersed into 50 mL of the dye solution with certain pH adjusted by NaOH or HCl solution. The mixture was continuously stirred gently. The maximum absorbance wavelength (␭max ) of dyes in water was measured by UV–vis spectrophotometer (UVT6, Beijing Purkinje General Instrument Co. Ltd, China). The removal (%) and adsorption amount (qt ) of dyes can be calculated according to Eqs. (1) and (2): removal(%) = qt =

C0 − Ct × 100% C0

(C0 − Ct )V W

(1) (2)

where C0 and Ct are the respective adsorbate concentration (mg L−1 ) in solution at initial time, and at time t. qt is the amount (mg g−1 ) of adsorbate adsorbed onto the microspheres adsorbents at time t. V is the volume of adsorbate solution (mL) and W is the dry weight of the adsorbents (mg). 2.7. Selective adsorption The cationic dye MB and anionic dyes of OR II and MO were selected to test the adsorption selectivity of MCA-E0.7 /CMC-gPDMDAAC microspheres. 10 mg microspheres were soaked into 50 mL of MB/ORII or MB/MO mixture (25 mg L−1 ) in water with certain pH adjusted by NaOH or HCl solution. The mixture was continuously stirred gently at room temperature, and the absorbances of dyes at a certain time in water were measured by UV–vis spectrophotometer. 2.8. Desorption and recycle of the MCA-E0.7 /CMC-g-PDMDAAC microspheres 10 mg MCA-E0.7 /CMC-g-PDMDAAC microspheres adsorbents were immersed into 50 mL of the dyes adsorption aqueous solution (50 mg L−1 ). When the adsorption equilibrium was reached, the adsorbents were separated. Then the separated adsorbents was put into 50 mL of distilled water as desorption solution with certain pH adjusted by NaOH or HCl solution at room temperature. The cumulation of dye desorbed was determined by UV–vis spectrophotometer. The desorption ratio (D%) can be calculated as Eq. (3): D(%) =

Cd Vd × 100% (C0 − Ce )Vi

(3)

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

285

where C0 and Ce are the initial and the equilibrium concentration of the dye in adsorption solution, Cd is the concentration of the dye in the desorption solution (mg L−1 ). Vi and Vd are the volume of the adsorption solution and the desorption solution (mL), respectively. After desorption, the recovered microspheres adsorbents were separated by suction filtration, and washed several times by distilled water till pH = 7. Then the adsorbents were immersed into the dye solution again for the re-adsorption, as Section 2.6 presented. 3. Results and discussion 3.1. Synthesis and characterization of the microspheres The synthesis of microspheres derived from CMC was illustrated in Scheme 1. ECH cross-linked CMC (E0.7 /CMC) microspheres were synthesized by inverse suspension crosslinking method. Based on the Williamson etherification and the alkali-catalyzed oxalkylation, the CMC chemically crosslinked by ECH to form hydrogels without the addition of an extra base (Salama et al., 2015; Yang, Fu, Zhou, Xie, & Li, 2011). Then, MCA were used to modify the E0.7 /CMC by the etherification reaction in alkaline conditions to obtain more anionic carboxyl groups. Finally, with potassium persulfate as initiator, DMDAAC as the graft cationic monomer, the novel and effective adsorbent, MCA-E0.7 /CMC-g-PDMDAAC microspheres were successfully synthesized by free radical mechanism, which with both cationic quaternary ammonium groups and anionic carboxyl groups. The microscopic images of E0.7 /CMC microspheres obtained by the polarizing microscope are shown in Fig. 1. E0.7 /CMC microspheres are characterized by relatively small and good dispersity, and with average diameters in a range of 50–70 ␮m in the original state.

Fig. 1. The microscopic image of E0.7 /CMC microspheres.

Fig. 2. show SEM images of E0.7 /CMC, MCA-E0.7 /CMC, and MCA-E0.7 /CMC-g-PDMDAAC microspheres. The surface of E0.7 /CMC exhibited spherical shape with a relative smooth surface (Fig. 2a). After reacted with MCA, the macroporous three-dimensional structure was constructed, with pore diameter in a very wide range of 30–100 ␮m (Fig. 2b). Moreover, more adjacent walls formed in MCA-E0.7 /CMC, and the BET surface areas increased obviously from 0.0885 to 0.2654 m2 g−1 , which is beneficial for DMDAAC grafted onto the surface of MCA-E0.7 /CMC. As shown in Fig. 2c, DMDAAC were successfully grafted onto the MCA-E0.7 /CMC, the surface of the microsphere has changed significantly, relatively denser surfaces

Fig. 2. SEM images of E0.7 /CMC (a), MCA-E0.7 /CMC (b), and MCA-E0.7 /CMC-g-PDMDAAC (c) microspheres.

286

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

Scheme 1. Illustration of E0.7 /CMC, MCA-E0.7 /CMC and MCA-E0.7 /CMC-g-PDMDAAC microspheres synthesis.

were detected in the MCA-E0.7 /CMC-g-PDMDAAC microspheres, and the expanded macroporous were shrinked compared with that of the MCA-E0.7 /CMC. The FTIR spectra of CMC, E0.7 /CMC, MCA-E0.7 /CMC, and MCAE0.7 /CMC-g-PDMDAAC microspheres are shown in Fig. 3. The broad absorption band at 3378–3442 cm−1 was relative to the −OH stretching vibration. The bands around 2923 cm−1 can be attributed to the asymmetric stretching vibration of C-H. And the absorption band around 1600 cm−1 , 1419 cm−1 and 1060 cm−1 can be attributed to the stretching vibration of COO− (asymmetric), COO− (symmetric) and C O C group, respectively (Homagai, Ghimire, & Inoue, 2010; Yan et al., 2011; Yang et al., 2011; Zhang et al., 2014). When the crosslinking reaction occurs between ECH and CMC, the absorption band of OH shifts from 3442 cm−1 to 3389 cm−1 (Fig. 3b), indicating the hydrogen bonds were formed and strengthened (Wang & Chen, 2016). After etherification with MCA, no obvious changes were found (Fig. 3c). For MCA-E0.7 /CMCg-PDMDAAC microspheres (Fig. 3d), the intensity of the absorption peak at 2923 cm−1 increased significantly, meanwhile the absorption band of −OH shifted toward 3441 cm−1 , which may due to the grafting polymerization occurs between −OH and DMDAAC and more methyl and methylene were formed, thus weaken the hydrogen bonds. In addition, two new bands at 2862 and 1458 cm−1 were observed, which are assigned to the C H symmetric stretching vibration and the shearing vibration of the CH2 and CH3 , respectively (Wang et al., 2014; Wu et al., 2014). And another new absorption peak at 1259 cm−1 can be assigned to the stretching vibration of C N bond. These results confirm the DMDAAC have been successfully grafted onto the surface of MCA-E0.7 /CMC microspheres. Meanwhile, the used MCA-E0.7 /CMC-g-PDMDAAC microspheres after three cycles in OR II adsorption at pH 2 and desorption with basic solution of pH at 11 were also analyzed by FTIR. The FTIR spectra of MCA-E0.7 /CMC-g-PDMDAAC before and after three recycles were almost unchanged (Fig. 4), suggesting that such MCAE0.7 /CMC-g-PDMDAAC adsorbents possess relatively good stability even under the low or high pH conditions.

The zeta potential of MCA-E0.7 /CMC-g-PDMDAAC microspheres at different pH values (Fig. 5) show that the pH of solution may change the surface charge of the microspheres and then influence its adsorption capacities. When the solution pH was lower than the point of zero charge (pHpzc , about 2.50), a positive zeta potential was showed due to the positively charged NR4 + groups. On the contrary when the solution pH is higher than pHpzc , the surface charge of the microspheres becomes negative, due to the more carboxyl groups −COOH were ionized to carboxylated groups COO− on its surface. This inferred that the MCA-E0.7 /CMC-g-PDMDAAC microspheres may adsorb anionic dyes from water when the solution pH < pHpzc , while adsorb cationic dyes under pH > pHpzc . 3.2. Adsorption behavior of the MCA-E0.7 /CMC-g-PDMDAAC microspheres 3.2.1. Effect of initial pH on dye adsorption MB was selected as the representative of cationic dye to probe the adsorption performance of MCA-E0.7 /CMC-g-PDMDAAC microspheres. The effect of pH on MB removal is presented in Fig. 6. When the solution pH was lower than pHpzc 2.50, the adsorbents show lower adsorption ability toward MB. It maybe due to that in such acidic condition, the carboxyl groups mainly existed as the COOH form, meanwhile the quaternized ammoniums repel the same charged MB molecules to access COO− , resulting that the attraction force between the surface of the adsorbent and MB molecules is weakened. On the contrary, the adsorption capacities increased sharply as the pH increase from 3 to 4, then increased slightly with the pH increase further. Under such circumstances, the carboxylated groups COO− becomes dominant, the number of carboxylated groups COO− outweighed that of the quaternary ammonium group, for the ionization degree of COOH group increased with the pH value, both improve MB adsorption. The maximum MB removal ratio reaches over 98.56% at pH 10. E0.7 /CMC almost could not adsorb anionic dyes, while grafting cationic monomer of DMDAAC to E0.7 /CMC, the adsorption ability toward anionic dyes highly increased. OR II was selected as the rep-

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

287

Fig. 3. FTIR spectra of CMC (a), E0.7 /CMC (b), MCA-E0.7 /CMC (c), and MCA-E0.7 /CMC-g-PDMDAAC (d) microspheres.

Fig. 4. FTIR spectra of MCA-E0.7 /CMC-g-PDMDAAC before (a) and after(b) three recycles in OR II adsorption–desorption. Table 1 The adsorption capacities of various adsorbents towards MB. Adsorbents

qmax (mg g−1 )

References

MCA-E0.7 /CMC-g-PDMDAAC Polydopamine microspheres Highly ordered mesoporous carbon Quince seed mucilage-magnetic iron oxide nanoparticles Iron terephthalate Cellulose nanocrystal-alginate

710.50 93.9 101.3 181 187 255.5

This work (Fu et al., 2016) (Moradi, 2014) (Hosseinzadeh & Mohammadi, 2015) (Haque, Jun, & Jhung, 2011) (Mohammed, Grishkewich, Waeijen, Berry, & Tam, 2016)

288

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

Fig. 5. Zeta potential of MCA-E0.7 /CMC-g-PDMDAAC microspheres at different pH values.

Fig. 6. Effect of pH of solution on MB and OR II adsorption onto MCA-E0.7 /CMC-g-PDMDAAC microspheres (10 mg adsorbents; 50 mL; [MB]0 = [OR II]0 = 50 mg L−1 ; room temperature; 30 min).

resentative of anionic dye to probe the adsorption performance of such MCA-E0.7 /CMC-g-PDMDAAC microspheres. As shown in Fig. 6, pH also plays an important role on OR II removal. When the solution pH was lower than pHpzc 2.50, the adsorbents show higher adsorption ability toward OR II, and the maximum adsorption efficiency to OR II appears at the pH value of 2 with a 71.73% removal ratio. And then the adsorption efficiency decreased with the pH increasing, after pH higher than 4. Based on the analysis of zeta potential study, when the solution pH is 2, the adsorbent showed a positive charge, which favorable for the electrostatic attraction between the anionic dyes OR II and the positive charged adsorbent. However, as the solution becomes more and more acidic (pH 1), only about 58.06% OR II can be adsorbed and removed. The reasons for this phenomenon may be that, when the solution is too acidic, the adsorbents begin to undergo ionization screening, thus leading

to weakened electrostatic attraction between the anionic dye OR II and the positive charged adsorbent (Yang et al., 2011). 3.2.2. Effect of contact time on MB and OR II adsorption The adsorption of MB or OR II onto the E0.7 /CMC and MCAE0.7 /CMC-g-PDMDAAC was investigated at room temperature. It was observed that both of the adsorbents have comparatively powerful adsorption ability towards MB (Fig. 7a). The adsorption equilibrium can be reached quickly within 15 min, and over 98.31% and 98.41% MB removal were obtained for E0.7 /CMC and MCA-E0.7 /CMC-g-PDMDAAC, respectively. Little differences were observed for the adsorption ability of MCA-E0.7 /CMC-g-PDMDAAC toward cationic dye of MB with that of E0.7 /CMC. While for anionic dyes of OR II (Fig. 7b), the OR II removal increased significantly from 4.47% to 71.73% at 30 min, obvious enhancement in adsorption abil-

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

289

Fig. 7. Effect of contact time on (a) MB adsorption (pH = 7), and (b) OR II adsorption (pH = 2) (10 mg adsorbents; 50 mL; [MB]0 = [OR II]0 = 50 mg L−1 ; room temperature). Table 2 The pseudo-first-order and pseudo-second-order kinetic parameters for MB and OR II adsorption on MCA-E0.7 /CMC-g-PDMDAAC microspheres. Dyes

Pseudo-first-order model −1

qe (mg g MB OR II

)

74.98 194.93

Experiment −1

k1 (min 0.17 0.14

)

2

−1

R

qe,exp (mg g

0.9045 0.8342

246.03 179.32

ity of MCA-E0.7 /CMC-g-PDMDAAC was observed. A longer contact time (30 min) was taken to reach the adsorption equilibrium. The adsorption abilities of MCA-E0.7 /CMC-g-PDMDAAC for MB and OR II were investigated at various concentrations ranging from 30 to 250 mg L−1 at room temperature (Fig. 8). At the beginning, the adsorption amount increases pronouncedly with the increase of the dye concentration, and then gradually reaches a plateau when the dye concentration is more than a certain limit. The maximum qe values of MCA-E0.7 /CMC-g-PDMDAAC are 710.50 and 200.50 mg g−1 for MB and OR II, respectively. Compared with the adsorption amount of several different adsorbents (Table 1), the MCA-E0.7 /CMC-g-PDMDAAC microspheres exhibited higher adsorption capacity towards cationic dye MB. 3.3. Kinetics study The adsorption kinetics are important to evaluate the adsorbent in terms of its adsorption efficiency and help to understand the mechanism of adsorption. Two typical kinetic models, pseudo-firstorder and pseudo-second-order equations, are analyzed, which are expressed by Eqs. (4) and (5), respectively: log(qe − qt ) = log qe − t 1 t = + qt qe k2 qe 2

k1 t 2.303

(4) (5)

where k1 and k2 are the pseudo-first-order and pseudo-secondorder rate constants, respectively, qe and qt are the adsorption amounts of dyes at equilibrium contact time and t min, respectively. A comparison of the results with the fitting line was plotted in Fig. 9 and the kinetic parameters were summarized in Table 2. It was observed that the correlation coefficients (R2 ) of pseudosecond-order model were higher than that of pseudo-first-order model. Also the qe calculated from Eq. (5) are also very close to the experimental qe values. Thus the adsorption process for MB and OR II in this study could describe better by the pseudo-second-order adsorption model. This indicates that the strength of ionic inter-

Pseudo-second-order model )

qe (mg g−1 )

k2 × 10−3 (g·mg−1 ·min−1 )

R2

248.76 189.39

7.38 1.39

0.9999 0.9973

action between the MCA-E0.7 /CMC-g-PDMDAAC and the dyes are the dominant (Fan et al., 2015). Therefore, the adsorption mechanism of dyes on the MCA-E0.7 /CMC-g-PDMDAAC microspheres may be described in Scheme 2. And the effect of initial pH on the MCA-E0.7 /CMC-g-PDMDAAC adsorption performance can be explained as follows: in the neutral or alkaline solution, majority of COOH groups were ionized to −COO− groups, thus the cationic dye of MB may interact with adsorbents through ionic attraction between cationic groups of MB and deprotonation of COO− groups of MCA-E0.7 /CMC-g-PDMDAAC. Along with the decrease of pH value, not only increases the number of cationic quaternary ammonium groups, but also partially or completely transform anionic COO− groups back into the COOH groups. Thus OR II may interact with adsorbents through ionic attraction between anionic sulfonate group of OR II and cationic quaternary ammonium groups of MCA-E0.7 /CMC-g-PDMDAAC microspheres. 3.4. Adsorption isotherms Equilibrium isotherms can provide useful information on the adsorption mechanism. In this study, Langmuir and Freundlich isotherms were used for clarifying the adsorption mechanism, both of which are widely used to simulate experimental data. The Langmuir and Freundlich models are expressed by Eqs (6) and (7), respectively: Ce 1 Ce = + qe qm KL qm log qe = log KF +

(6) 1 log Ce n

(7)

where qe (mg g−1 ) and qm (mg g−1 ) are the equilibrium adsorption amount of adsorbate and the monolayer saturation adsorption amount on the adsorbent, respectively. The KL and KF are the Langmuir and Freundlich isotherm constant, respectively. And the n is heterogeneity factor and have been used to describe adsorption intensity of the adsorbent. The fitting lines were plotted in Fig. 10 and the isotherm parameters were summarized in Table 3.

290

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

Fig. 8. Effect of initial concentration on MB (pH = 7) and OR II adsorption (pH = 2) (10 mg adsorbents; 50 mL; room temperature; 30 min).

Fig. 9. The pseudo-first-order kinetics (a) and pseudo-second-order kinetics (b) for MB and OR II adsorption on MCA-E0.7 /CMC-g-PDMDAAC microspheres. Table 3 Langmuir and Freundlich isotherm parameters for the adsorption of MB and OR II on MCA-E0.7 /CMC-g-PDMDAAC microspheres. Langmuir −1

Dyes qm (mg g MB 709.22 OR II 197.24

Experiment ) KL (L mg 0.61 0.50

−1

2

) R

−1

qe,max (mg g

0.9987 710.50 0.9976 200.50

Freundlich ) n

KF (mg L−1 ) R2

4.35 278.01 8.99 116.27

0.8129 0.5161

It is apparent that the Langmuir isotherm fitted better to the experimental data compared to the Freundlich model. In addition, the monolayer saturation adsorption amount (qm ) calculated from Eq. (6) is also very close to the calculated value (qe,max ), which indicating that monolayer coverage of the adsorbate is the main adsorption mechanism due to homogenous distribution of active sites on the surface of MCA-E0.7 /CMC-g-PDMDAAC microspheres (Karaca, Gürses, Ac¸ıkyıldız, & Ejder (Korucu), 2008).

3.5. Selective adsorption property of MCA-E0.7 /CMC-g-PDMDAAC microspheres The above experiments demonstrate that such adsorbent MCAE0.7 /CMC-g-PDMDAAC microspheres show excellent adsorption ability towards cationic dye of MB when the solution pH was neutral or alkaline. In this section, the selective adsorption property of MCA-E0.7 /CMC-g-PDMDAAC for the cationic dye MB from the MB/OR II or MB/MO mixture were investigated at pH 7 and 2 (Fig. 11). Obvious changes in the color were only observed at pH 7 before and after adsorption. The reasons for this phenomenon may be due to that the cationic dye of MB may interact with anionic sulfonate group of OR II or MO when the adsorption solution is in such acidic condition. The UV–vis spectra also demonstrated that the maximum absorbance wavelength (␭max ) of OR II at 484 nm and MO at 464 nm shifted to 492 nm to 506 nm, respectively. Therefore the interaction between cationic dyes of MB and anionic dyes of OR II and MO may be described in Scheme 3.

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

291

Scheme 2. Possible adsorption mechanism of MB (A) and OR II (B) on MCA-E0.7 /CMC-g-PDMDAAC microspheres.

3.6. Desorption and recycle of the MCA-E0.7 /CMC-g-PDMDAAC microspheres

Scheme 3. The interaction between MB and anionic dyes of OR II or MO.

3.6.1. Dye desorption of MCA-E0.7 /CMC-g-PDMDAAC microspheres According to the above discussion it is known that ionic interaction is the dominant in the dye adsorption by MCAE0.7 /CMC-g-PDMDAAC microspheres. And the numbers of cationic and anionic groups of MCA-E0.7 /CMC-g-PDMDAAC can be controlled by adjusting the pH of solution. Therefore the desorption experiments for cationic dye of MB were mainly performed under acidic condition, due to the negative COO− groups were protonated by H+ , and thus decrease the electrostatic attraction between the surface of the adsorbent and the cationic dye of MB. Furthermore, the repelling force between MB and MCA-E0.7 /CMC-g-PDMDAAC also enhance in such acidic condition as the number of positive

Fig. 10. Langmuir (a), and Freundlich (b) adsorption isotherm for MB and OR II adsorption on MCA-E0.7 /CMC-g-PDMDAAC microspheres.

292

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

Fig. 11. Time-dependent UV–vis spectra of MB/OR II or MB/MO mixture in the presence of MCA-E0.7 /CMC-g-PDMDAAC microspheres (10 mg adsorbents; 50 mL; [MB]0 = [OR II]0 = [MO] = 25 mg L−1 ; room temperature).

Fig. 12. Desorption ratio of MB and OR II at different time (10 mg adsorbents; 50 mL of distilled water at pH 3(MB) or 11(OR II); room temperature).

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

293

Fig. 13. Recycle of adsorbents for MB (pH 7) and OR II (pH 2) adsorption (10 mg adsorbents; 50 mL; room temperature; 30 min).

NR4 + groups increase. MB desorption from adsorbents at pH of 3 are shown in Fig. 12. Over 98.54% of MB can be desorbed within 20 min, indicating the high performance of desorption capacities of MCA-E0.7 /CMC-g-PDMDAAC. As for anionic dye, the desorption experiments for OR II were performed under basic solution (pH 11), due to the increasing number of deprotonated groups of COO− would decrease the interaction between the surface of the adsorbent and the anionic dye of OR II. Almost the same as that the desorption tendency of MB and OR II, and about 83.07% of OR II can be desorbed. As experiments demonstrated such MCA-E0.7 /CMCg-PDMDAAC microspheres exhibited a good reversibility for the adsorption and desorption of dyes. It suggested that this important characteristic of MCA-E0.7 /CMC-g-PDMDAAC microspheres may be useful for the application in controlled-releasing of drug. 3.6.2. Recycle of MCA-E0.7 /CMC-g-PDMDAAC microspheres The recycle of the MCA-E0.7 /CMC-g-PDMDAAC microspheres adsorbent was investigated by successively performing the adsorption–desorption cycles for three times. As seen in Fig. 13, although the dye adsorption performances of the adsorbents decreased slightly from 230 to 210 mg g−1 for MB, and 172–149 mg g−1 , respectively, the adsorbents still show good adsorption capacities for MB and OR II. This clearly demonstrated the MCA-E0.7 /CMC-g-PDMDAAC microspheres were easy to recycle without significant loss of adsorption ability, which was consistent with the FTIR spectra. 4. Conclusion The effective MCA-E0.7 /CMC-g-PDMDAAC microspheres adsorbent by graft DMDAAC onto the chain of MCA modified ECH cross-linked CMC with both NR4 and COOH groups were successfully synthesized, with pH-sensitive adsorption properties towards cationic and anionic dyes. The MCA-E0.7 /CMC-g-PDMDAAC microspheres show excellent adsorption ability towards cationic dye of MB under neutral or alkaline condition, with maximum adsorption capacity 710.50 mg g−1 . Moreover, the MCA-E0.7 /CMCg-PDMDAAC could effectively adsorb anionic dye OR II at pH was lower than 3, with the maximum adsorption capacity 200.50 mg g−1 . Meanwhile MCA-E0.7 /CMC-g-PDMDAAC can adsorb selectively the cationic dye MB from the mixture of cationic and

anionic dyes (MB/OR II or MB/MO mixture) under neutral condition. The desorption were performed under acidic (pH 3) for MB or basic (pH 11) for OR II, over 98.54% of MB and 83.07% of OR II can be desorbed within 20 min, respectively. The adsorption kinetics and isotherm fit better the pseudo-second-order kinetic and Langmuir model, respectively. Such MCA-E0.7 /CMC-g-PDMDAAC microspheres, exhibited good pH-sensitive and selective adsorption ability towards certain dyes and show high performance of desorption abilities of dyes, indicating that it can be act as potential material for removing synthetic dyes in waste water and even further studies to use in other specific application. Acknowledgment The authors are grateful to be supported by the Fundamental Research Funds for the Central Universities (GK201302013). References Algarra, M., Isabel Vázquez, M., Alonso, B., Casado, C. M., Casado, J., & Benavente, J. (2014). Characterization of an engineered cellulose based membrane by thiol dendrimer for heavy metals removal. Chemical Engineering Journal, 253, 472–477. Amin, M. C. I. M., Ahmad, N., Halib, N., & Ahmad, I. (2012). Synthesis and characterization of thermo-and pH-responsive bacterial cellulose/acrylic acid hydrogels for drug delivery. Carbohydrate Polymers, 88, 465–473. Bulut, Y., & Karaer, H. (2015). Adsorption of methylene blue from aqueous solution by crosslinked chitosan/bentonite composite. Journal of Dispersion Science and Technology, 36, 61–67. Chan, S. H. S., Wu, T. Y., Juan, J. C., & Teh, C. Y. (2011). Recent developments of metal oxide semiconductors as photocatalysts in advanced oxidation processes (AOPs) for treatment of dye waste-water. Journal of Chemical Technology and Biotechnology, 86, 1130–1158. Chen, Y., Liu, Y., Tang, H., & Tan, H. (2010). Study of carboxymethyl chitosan based polyampholyte superabsorbent polymer: I Optimization of synthesis conditions and pH sensitive property study of carboxymethyl chitosan-g-poly(acrylic acid-co-dimethyldiallylammoniumchloride) superabsorbent polymer. Carbohydrate Polymers, 81(2010), 365–371. Chung, K. T. (2000). Mutagenicity and carcinogenicity of aromatic amines metabolically produced from azo dyes. Environment Carcinogenesis and Ecotoxicology Reviews, 18, 51–71. Deng, C., Liu, J., Zhou, W., Zhang, Y. K., Du, K. F., & Zhao, Z. M. (2012). Fabrication of spherical cellulose/carbon tubes hybrid adsorbent anchored with welan gum polysaccharide and its potential in adsorbing methylene blue. Chemical Engineering Journal, 200, 452–458. Fan, Y., Liu, H. J., Zhang, Y., & Chen, Y. (2015). Adsorption of anionic MO or cationic MB from MO/MB mixture using polyacrylonitrile fiber hydrothermally treated

294

Q. Lin et al. / Carbohydrate Polymers 151 (2016) 283–294

with hyper-branched polyethylenimine. Journal of Hazardous Materials, 283, 321–328. Fu, J., Xin, Q., Wu, X., Chen, Z., Yan, Y., Liu, S., et al. (2016). Selective adsorption and separation of organic dyes from aqueous solution on polydopamine microspheres. Journal of Colloid and Interface Science, 461, 292–304. Gadd, G. M. (2009). Biosorption: critical review of scientific rationale: environmental importance and significance for pollution treatment. Journal of Chemical Technology and Biotechnology, 84, 13–28. Gao, M. F., Ma, Q. L., Lin, Q. W., Chang, J. L., Bao, W. R., & Ma, H. Z. (2015). Combined modification of fly ash with Ca(OH)2 /Na2 FeO4 and its adsorption of Methyl orange. Applied Surface Science, 359, 323–330. Girods, P., Dufour, A., Fierro, V., Rogaume, Y., Rogaume, C., & Zoulalian, A. (2009). A. Celzard Activated carbons prepared fromwood particleboard wastes: characterisation and phenol adsorption capacities. Journal of Hazardous Materials, 166, 491–501. Hameed, B. H., Din, A. T. M., & Ahmad, A. L. (2007). Sorption of methylene blue onto bamboobased activated carbon: kinetics and equilibrium studies. Journal of Hazardous Materials, 141, 819–825. Haque, E., Jun, J. W., & Jhung, S. H. (2011). Adsorptive removal of methyl orange and methylene blue from aqueous solution with a metal-organic framework material, iron terephthalate (MOF-235). Journal of Hazardous Materials, 185, 507–511. Homagai, P. L., Ghimire, K. N., & Inoue, K. (2010). Sorption behavior of heavy metals onto chemically modified sugarcane bagasse. Bioresource Technology, 101, 2067–2069. Hosseinzadeh, H., & Mohammadi, S. (2015). Quince seed mucilage magnetic nanocomposites as novel bioadsorbents for efficient removal of cationic dyes from aqueous solutions. Carbohydrate Polymers, 134, 213–221. Karaca, S., Gürses, A., Ac¸ıkyıldız, M., & Ejder (Korucu), M. (2008). Adsorption of cationic dye from aqueous solutions by activated carbon. Microporous Mesoporous Mater, 115, 376–382. Liu, J. S., Ma, S., & Zang, L. J. (2013). Preparation and characterization of ammonium-functionalized silica nanoparticle as a new adsorbent to remove methyl orange from aqueous solution. Applied Surface Science, 265, 393–398. Liu, X. X., Gong, W. P., Luo, J., Zou, C. T., Yang, Y., & Yang, S. J. (2016). Selective adsorption of cationic dyes from aqueous solution by polyoxometalate-based metal-organic framework composite. Applied Surface Science, 362, 517–524. Martínez-Huitle, C. A., & Brillas, E. (2009). Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods: a general review. Applied Catalysis B: Environmental, 87, 105–145. Mittal, A., Mittal, J., Malviya, A., Kaur, D., & Gupta, V. (2010). Decoloration treatment of a hazardous triarylmethane dye: light Green SF (Yellowish) by waste material adsorbents. Journal of Colloid and Interface Science, 342, 518–527.

Mohammed, N., Grishkewich, N., Waeijen, H. A., Berry, R. M., & Tam, K. C. (2016). Continuous flow adsorption of methylene blue by cellulose nanocrystal-alginate hydrogel beads in fixed bed columns. Carbohydrate Polymers, 136, 1194–1202. Moradi, S. E. (2014). Microwave assisted preparation of sodium dodecyl sulphate (SDS) modified ordered nanoporous carbon and its adsorption for MB dye. Journal of Industrial and Engineering Chemistry, 20, 208–215. Rafatullah, M., Sulaiman, O., Hashim, R., & Ahmad, A. (2010). Sorption of methylene blue on low-cost sorbents: a review. Journal of Hazardous Materials, 177, 70–80. Salama, A., Shukry, N., & El-Sakhawy, M. (2015). Carboxymethyl cellulose-g-poly (2-(dimethylamino) ethylmethacrylate) hydrogel as adsorbent for dye removal. International Journal of Biological Macromolecules, 73, 72–75. Teh, C. M., & Mohamed, A. R. (2011). Roles of titanium dioxide and ion-doped titanium dioxide on photocatalytic degradation of organic pollutants (phenolic compounds and dyes) in aqueous solutions: a review. Journal of Alloys and Compounds, 509, 1648–1660. Wang, Q. Q., & Chen, D. J. (2016). Synthesis and characterization of a chitosan based nanocomposite injectable hydrogel. Carbohydrate Polymers, 136, 1228–1237. Wang, Z. G., Fan, X. L., He, M., Chen, Z. Q., Wang, Y. F., Ye, Q. F., et al. (2014). Construction of cellulose-phosphor hybrid hydrogels and their application for bioimaging. Journal of Materials Chemistry B, 2, 7559–7566. Wu, X. P., Gao, P., Zhang, X. L., Jin, G. P., Xu, Y. Q., & Wu, Y. C. (2014). Synthesis of clay/carbon adsorbent through hydrothermal carbonization of cellulose on palygorskite. Applied Clay Science, 95, 60–66. Yan, H., Zhang, W. X., Kan, X. W., Dong, L., Jiang, Z. W., Li, H. J., et al. (2011). Sorption of methylene blue by carboxymethyl cellulose and reuse process in a secondary sorption. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 380, 143–151. Yang, S. P., Fu, S. Y., Zhou, Y. M., Xie, C. L., & Li, X. Y. (2011). Preparation and release properties of a pH-tunable carboxymethyl cellulose hydrogel/methylene blue host/guest model. International Journal of Polymeric Materials, 60, 62–74. Zhang, L., Han, J. J., Li, J. J., & Liu, T. Q. (2013). Properties and spreading kinetics of water-based cypermethrin microemulsions. Acta Physico-Chimica Sinica, 29, 346–350. Zhang, Y. L., Liu, Y., Wang, X. R., Sun, Z. M., Ma, J. K., Wu, T., et al. (2014). Porous graphene oxide/carboxymethyl cellulose monoliths: with high metal ion adsorption. Carbohydrate Polymers, 101, 392–400. Zhang, G., Shi, L., Zhang, Y. L., Wei, D., Yan, T., Wei, Q., et al. (2015). Aerobic granular sludge-derived activated carbon: mineral acid modification and superior dye adsorption capacity. RSC Advances, 5, 25279–25286.