International Journal of Biological Macromolecules 66 (2014) 172–178

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

Preparation of magnetic ionic liquid/chitosan/graphene oxide composite and application for water treatment Leilei Li, Chuannan Luo ∗ , Xiangjun Li, Huimin Duan, Xiaojiao Wang Key Laboratory of Chemical Sensing & Analysis in Universities of Shando ng (University of Jinan), School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, China

a r t i c l e

i n f o

Article history: Received 16 December 2013 Received in revised form 6 February 2014 Accepted 13 February 2014 Available online 21 February 2014 Keywords: Magnetic chitosan Graphene oxide Ionic liquid Adsorption Langmuir Cr(VI)

a b s t r a c t Magnetic chitosan and graphene oxide-ionic liquid (MCGO-IL) composites as biodegradable biosorbents were synthesized by impregnating MCGO with ionic liquid. The characteristic results of FTIR, SEM, and XRD showed that MCGO-IL were successfully prepared with large surface area and good magnetic responsiveness. They were used for the removal of Cr(VI) from simulated wastewater with a fast solid–liquid separation in the presence of external magnetic field. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, contact time, and initial ion concentration were studied in detail. The adsorption followed a pseudo-second-order kinetics. The equilibrium adsorption was well-described by the Langmuir isotherm mode and the maximum adsorption capacity was 145.35 mg/g. The stronger intermolecular hydrogen bond between MCGO-IL and Cr(VI) and the hydroxyl and amine groups were believed to be the metal ion binding sites. Moreover, the MCGO-IL could be repeatedly used by simple treatment without obvious structure and performance degradation. The obtained results indicated that the impregnation of the room temperature IL significantly enhances the removal efficiency of Cr(VI). The MCGO-IL may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Toxic heavy metal ions in water bring many detrimental effects on environment and human health [1–3]. Among those heavy metal species, Cr(VI) is a commonly identified contaminant because of its high toxicity and mobility [4]. Chromium compounds are mainly used in electroplating, tannery and dyeing industries [5], their waste discharge is of prime concern. With better awareness of these problems, a number of technologies to remove Cr(VI) have been developed, including cyanide treatment [6], electro-chemical precipitation [7], reverse osmosis (RO) [8,9], ion exchange (IE) [10,11] and adsorption [12]. From the literature query, various adsorbents have been reported to remove Cr(VI) from wastewater, such as clay minerals, oxides, and zeolites [13–15]. However, separating and recycling these materials turn out to be a challenge especially when the particle size goes down to nanoscale and thus reducing the operation time in each cycle is urgently required in modern industry.

∗ Corresponding author. Tel.: +86 53189736065. E-mail address: chm yfl[email protected] (C. Luo). http://dx.doi.org/10.1016/j.ijbiomac.2014.02.031 0141-8130/© 2014 Elsevier B.V. All rights reserved.

Nanostructured adsorbents exhibited remarkable advantages due to their higher surface areas and much more surface active sites than bulk materials [16,17]. However, there are two major challenges when using these nanomaterials. One comes from the easy oxidation/dissolution of the pure nanoparticles such as Fe nanoparticles (NPs), especially in acidic solution. The other is the difficulty to recycle these nanomaterials with such a small size. Hence, it is very urgent to develop new materials with large surface area, high adsorption capacity and stability to apply in water treatment. More recently, Wang et al. [18] have reported the high capacity adsorption of hexavalent chromium using magnetic microspheres with dendrimer modification. Crini [19] has reviewed the importance of biopolymers in wastewater treatment. The biodegradability and excellent stability coupled with the active binding sites makes them well suited for adsorption of heavy metals. Prominent among the biopolymers is chitosan, because chitosan contains many oxygen-containing functional groups. Graphene oxide (GO) contains a wide range of oxygen functional groups both on the basal planes and at the edges of GO sheets, such as –COOH, and –OH. These functional groups are essential for the high sorption of heavy metal ions, and allows GO to participate in a wide range of bonding interactions. GO shows high adsorption performance of metal ions, but cannot be easily separated from

L. Li et al. / International Journal of Biological Macromolecules 66 (2014) 172–178

treated water. In addition, the chitosan and graphene oxide are easy to aggregate, resulting in great reduction in the surface area, and is not beneficial for the adsorption of contaminants. Therefore, it is of great importance to develop nanostructured adsorbents with easy solid–liquid separation property. As a potential environment-friendly solvent, room temperature ionic liquid (IL) has received intense scrutiny [20]. They have also been successfully applied in the area of separation science [21]. Recently, IL is receiving much attention owing to their unique properties, such as good ionic conductivity, wide potential window, high viscosity, high thermal stability, tunable solvent properties and low toxicity [22]. Based on the strong electrostatic/chemical interaction between IL and GO as well as improved dispersion of GO by IL [23], furthermore, the introduction of IL into functional composites could improve the performance of the corresponding composites and give rise to a wider range of applications [24]. Therefore, great efforts have been made towards the preparation of the IL functionalized GO composites. In addition, chitosan can also be dissolved, regenerated, and functionalized through the IL processing [25]. Accordingly, the synthesis of environment-friendly IL-functionalized composites and use them to solve environmental problems is of great significance. In this paper, we introduced Fe3 O4 particles to synthesize magnetic chitosan and graphene oxide (MCGO), and then we report the utility of MCGO as an excellent platform for impregnating the ionic liquid to formed MCGO-IL. The introduction of the magnetic could well solve the problem of difficult to separation, and the IL not only increase the water-solubility of the composite material but also could adsorb metal ions collaborate with MCGO by electrostatic attraction. The effects of the treatment time, initial ion concentration and pH values on the Cr(VI) removal are investigated for the prepared MCGO-IL. The adsorption kinetics is also investigated by fitting the experimental data with different models and the removal mechanism is proposed. The MCGO-IL are found to possess unique capability to remove Cr(VI) very quickly and efficiently from wastewater. 2. Experimental 2.1. Materials Chitosan with 80 mesh, 96% degree of deacetylation and average-molecular weight of 6.36 × 105 was purchased from Qingdao Baicheng Biochemical Corp. (China). FeCl2 ·4H2 O and FeCl3 ·6H2 O were purchased from Damao Chemical Agent Company (Tijin, China). The reagents 1-ethyl-3-(3-dimethylaminoprophy) carbondiimide hydrochloride (EDC), N-hydroxyl succinimide (NHS), sodium hydroxide, glutaradehyde and acetic acid were Aldrich products, tetraoctylammonium bromide were purchased from Sigma Aldrich. Sulfuric acid was procured from Merck, India. All other reagents used in this study were analytical grade, and distilled or double distilled water was used in the preparation of all solutions. 2.2. Preparation of MCGO GO was prepared from purified natural graphite by the modified Hummers method [26]. Magnetic chitosan and graphene oxide was prepared following the method of Fan L. et al. [27]. A solution of 0.05 M EDC and 0.05 M NHS was added to the GO dispersion with continuous stirring for 2 h in order to activate the carboxyl groups of GO [28]. To adjust the pH of the resulting solution was maintained at 7.0. 0.1 g of magnetic chitosan and the activated GO solution were added in a flask and dispersed in distilled water by

173

Scheme 1. Synthesis of MCGO-IL.

ultrasonic dispersion for 10 min. After ultrasonic dispersion, the mixed solutions were stirred at 60 ◦ C for 2 h. The precipitate was washed with 2% (w/v) NaOH and distilled water in turn until pH was about 7. Then, the obtained product was collected by the aid of an adscititious magnet and dried in a vacuum oven at 50 ◦ C. The obtained product was MCGO. 2.3. Preparation of MCGO-IL MCGO-IL was prepared following the method of Santhana Krishna Kumara et al. [29]. 1.0 g of tetraoctylammonium bromide was dissolved in 15 mL methanol. 1.0 g of MCGO was taken in a round bottom flask and the dissolved ionic liquid was added dropwise and sonicated (Ultrasonic bath, Biotechnics, India) for 2 h with a 15 min intermittent time interval. The resulting solution was filtered, washed with methanol and the resulting IL impregnated MCGO was dried at room temperature and used for further adsorption studies. The preparation of MCGO-IL is shown in Scheme 1. 2.4. Characterization methods A HH-15 vibrating sample magnetometer (Nanjing, China) was used to measure magnetization curve of samples. Wide angle X-ray diffraction (WAXRD) patterns were recorded by a D8 ADVANCE Xray diffraction spectrometer (Bruker, German) with a Cu K␣ target at a scan rate of 0.02◦ 2 s−1 from 10◦ to 80◦ . Morphological structures of samples were examined by scanning electron microscopy (SEM) with a Hitachi SX-650 machine (Tokyo, Japan). FT-IR spectra were measured on a Perkin-Elmer 580B IR spectrophotometer using the KBr pellet technique. 2.5. Adsorption experiments All batch adsorption experiments were performed on a model KYC-1102 C thermostat shaker (Ningbo, China) with a shaking speed of 180 rpm. Simulated wastewater with different Cr(VI) concentrations (60, 80, 100, 120, 140, 160, 180, 200 mg L−1 ) were prepared by dilution of the stock K2 Cr2 O7 standard solution with DI water. MCGO-IL (0.10 g) were added to 100 mL of the above Cr(VI) solution under mechanical agitation. For all adsorption tests, the initial pH values of the Cr(VI) solution were adjusted with 0.1 mol L−1 HCl solution or 0.1 mol L−1 NaOH solution. After the adsorption processes, MCGO-IL was conveniently separated by magnetic separation and the supernatant was immediately analyzed by atomic absorption spectrometry (WFX-1F2, China). To study the influence of initial pH on the removal of Cr(VI), the initial pH values of the solution were adjusted to 3.0, 4.0, 5.0, 6.0, 7.0 and 10.0. The concentration of MCGO-IL was 1.0 g L−1 , and the initial Cr(VI) concentration was 100 mg L−1 . The adsorption capacity and adsorption rate are calculated based on the difference in the Cr(VI)

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Fig. 1. (a) SEM images of the GO, (b) MCGO and (c) MCGO-IL.

concentration in the aqueous solution before and after adsorption, according to the following equation: Q =

(C0 − Ce )V (C0 − Ce ) , E= × 100% W C0

(1)

where C0 and Ce are the initial and equilibrium concentrations of Cr(VI) in milligrams per liter, respectively, V the volume of Cr(VI) solution, in liters, and W is the weight of the MCGO-IL used, in grams. 2.6. Replication of batch experiment Each batch adsorption experiment was conducted twice and the data shown are the average values. The individual values were generally within 5%. 3. Results and discussion 3.1. Characterization of MCGO-IL The typical SEM micrograph of the GO, MCGO and MCGO-IL composite are shown in Fig. 1. From Fig. 1a, it can be seen clearly that GO sheets presents the sheet-like structure with smooth surface and wrinkled edge. The obtained GO display layered structures and become very thin. After combination with magnetic chitosan to form the MCGO composite (Fig. 1b), the MCGO had a rougher surface, which reveals that many magnetic chitosan clusters had been assembled on the surface of the GO layers. The surface morphology of the prepared MCGO-IL was shown in Fig. 1c, a morphological difference can be observed between the MCGO and MCGO-IL. Some aggregated microparticles are observed on the surface of MCGO-IL.

The MCGO-IL is porous with much rougher surface, which indicates MCGO-IL has large surface area surface. The significant structural changes occurring during the chemical reduction process from GO to the MCGO-IL were also reflected in the powder X-ray diffraction patterns. As shown in Fig. 2a, the broad and relatively weak diffraction peak at 2 = 10.03◦ (d = 0.87 nm), which corresponds to the typical diffraction peak of graphene oxide nanosheets, is attributed to the (0 0 2) plane. The characteristic peaks of chitosan are observed at 2 = 20.16◦ [30]. In addition, from Fig. 2a, it can be seen that six characteristic peaks for Fe3 O4 (2 = 30.1, 35.5, 43.3, 53.4, 57.2 and 62.5), marked by their indices (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) are observed in Fe3 O4 and MCGO-IL, which indicates the adsorbent has good magnetic properties and can be used for the magnetic separation. Fig. 2b shows the MCGO-IL in external magnetic field. It can be seen that after being exposed to an external magnetic field, all the MCGOIL could be rapidly separated from the solution. The result of this simple magnetic separation experiment confirms that the MCGOIL composite is magnetic and can be used as a magnetic adsorbent to remove pollutants from large volumes of aqueous solutions in real work. The FTIR pattern of GO, which is shown in Fig. 3, reveals the presence of the oxygen-containing functional groups. The peaks at 1057, 1226, 1655 correspond to C–O–C stretching vibrations, C–OH stretching, C–C stretching mode of the sp2 carbon skeletal network, respectively. While peaks located at 1712, and 3428 cm−1 correspond to C–O stretching vibrations of the –COOH groups, and O–H stretching vibration, respectively [28]. As shown in Fig. 3, the peaks at 1654, 1570, 1405 cm−1 correspond to C–O stretching vibrations of –NHCO, N–H bending of NH2 , and C–N bending vibration. However, there is almost no N in the surface of GO and the –NH2 absorbance band has shifted to a lower value and the intensity of

Fig. 2. (a) XRD patterns of the Fe3 O4 , GO and the MCGO-IL, and (b) The MCGO-IL in external magnetic field.

90 85 80 75 70 65 60 55 50 45 40

MCGO-IL

1560

1383

580 1405

MCGO

Qe(mg/g)

T/%

L. Li et al. / International Journal of Biological Macromolecules 66 (2014) 172–178

1654 1570

GO

1712

1655 1057 1226

3428

100 95 90 85 80 75 70 65 60 55 50 3

0

1000

2000

3000

4

5

6

7

11

HCrO4 − + 7H+ + 3e ↔ Cr3+ + 4H2 O Therefore, a large amount of protons were consumed during the adsorption and the reduction of HCrO4 − . In addition, the electrostatic attraction between HCrO4 − and IL cation is very important in the adsorbent process. The proposed adsorption mechanism of Cr(VI) is shown in Fig. 5. On the basis of the above results, we proposed a possible Cr(VI) removal mechanism, it may consists of four steps: (1) The −OH protonated to formed −OH2 + , and then adsorption of Cr(VI) by electrostatic attraction; (2) The formed of −NH3 + to adsorbed Cr(VI) by electrostatic attraction; (3) The cooperation between IL, the functional groups of the adsorbent and the Cr(VI); (4) Cr(VI) is reduced to Cr(III) with the assistance of ␲ electrons on the carbocyclic six-membered ring of MCGO-IL, the release of Cr(III) species into solution by electrostatic repulsion between the protonated amine groups and the cation Cr(III), or the binding of Cr(III) species on

3.2. Effect of pH There are several forms of Cr(VI) ion exist in solution, they are chromate (CrO4 2− ), dichromate(Cr2 O7 2− ) and hydrogen chromate(HCrO4 − ), and these ion forms are related to the solution pH and total chromate concentration [31,32]. Under alkaline conditions, the yellow chromate oxo-anion is the major species, where as in acidic medium, the Cr2 O7 2− and HCrO4 − oxo-anions are the predominant species [33]. So the pH is one of the most important variables affecting the adsorption characteristics. The effect of initial solution pH on the removal of Cr(VI) by MCGO-IL was investigated, it shows in Fig. 4.

O

O

OH

O

Cr(III)

Cr

Cr

O -

O

(4)

) (2

(3)

NH3+

OH2

Cr(III)

(Br-) N+

N

+

MCGO-IL

e-

NH3+

-) (Br

N+

OH

+ (Br-) N

O-

Cr3+

10

It can be seen from Fig. 4 that the adsorbent has the maximum adsorbing capacity when pH in the range 3–4. At lower pH, plenty of hydroxyl groups on the surface of MCGO-IL would be protonation from −OH to −OH2 + , −NH2 to −NH3 + , and they could absorb negatively charged HCrO4 − through electrostatic attraction. Meanwhile, low pH also promotes the redox reactions in the aqueous and solid phases, because the protons could participate in the following reaction as follows [34]

acetylated amino group –NHCO has increased, which proves that -NH2 groups on the chitosan have been reacted with the –COOH groups of GO and therefore have been converted to –NHCO– graft points. In addition, 580 cm−1 is the characteristic peak of Fe3 O4 . These indicated that GO was successfully grafted on magnetic chitosan. The major peaks for MCGO-IL in Fig. 3 can be assigned as follows: The peaks located at 1560 and 1383 cm−1 correspond to N–H and C–N bending vibration. It can be seen that the bending vibration of N–H and C–N shifted to a lower value. These changes may be due to the hydrogen bond between tetraoctylammonium bromide cation and MCGO. These indicated that the MCGO-IL has been successfully synthesized.

Cr(III)

9

Fig. 4. Effect of pH on the adsorption of Cr(VI) on the MCGO-IL. The concentration of MCGO-IL was 1.0 g L−1 . The initial Cr(VI) ion concentrations was 100 mg L−1 . The contact time was 40 min. The temperature was 303 K.

Fig. 3. IR spectra of pure GO, MCGO and MCGO-IL.

OH2+

8

pH

4000

Wavelength/cm

(1 )

175

(Br-) IL H+

e- Electron donor -COO-

Fig. 5. Proposed mechanism of Cr(VI) removal by MCGO-IL.

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L. Li et al. / International Journal of Biological Macromolecules 66 (2014) 172–178

(a) 100

(b) 1.6

1.2

60

t/ Qe

Qe(mg/g)

80

40

0.4

20 0

0.8

0

20

40

60

80

100 120

0.0

20

40

60

t/min

80

100

120

t/min

Fig. 6. (a) Time profile of Cr(VI) ion removal with MCGO-IL. (b) The pseudo-second-order model. The initial Cr(VI) ion concentrations was 100 mg L−1 . The concentration of MCGO-IL was 1.0 g L−1 . The pH 3.0. The temperature was 303 K.

MCGO-IL by the electrostatic attraction between Cr(III) and negatively charged groups (–COO−) of MCGO-IL. Above pH 4, and in the alkaline range, the decrease in the percentage adsorption could be attributed to the deprotonation of the surface amino group and consequent competition of the hydroxide ion for the active adsorption sites [35]. 3.3. Adsorption kinetics The first-order and pseudo-second-order models were used to fit the experimentally obtained adsorption data. The first-order [36] and the pseudo-second-order rate equations [37] are expressed. The pseudo-first-order equation of Lagergren is expressed as follows: log(qe − qt ) = log(qe ) −

 k  1 2.303

t

(2)

The pseudo-second-order equation is expressed as follows: 1 t = + qt k2 q2e

1 qe

t

(3)

where qe and qt are the adsorption capacity (mg/g) at equilibrium and at time t (min), respectively, and k1 is the rate constant of pseudo-first-order adsorption (1/min). Where k2 is the rate constant of pseudo-second-order adsorption (g mg−1 min−1 ). To estimate the suitability of different models, it is necessary to introduce the correlation coefficient (R2 , close or equal to 1). The higher R2 value of pseudo-second-order model indicates that the pseudosecond-order model is a more applicable model to the kinetics of Cr(VI) adsorption [38]. The results are shown in Fig. 6. It can be seen from Fig. 6(a) that the adsorbent showed a good performance in adsorption during the first 40 min, and the adsorbing capacity had no obviously enhance with increasing the time. It indicated that the MCGO-IL was able to quickly reach adsorption equilibrium. The experimental data shows a good fit to pseudosecond-order model indicates that MCGO-IL can be a very good adsorption of Cr(VI).

The linear form of the Freundlich model could be expressed as follows [40]: ln qe = ln KF +

ce 1 ce = + qe qm (KL qm )

(4)

(5)

where ce is the equilibrium concentration of Cr(VI) in aqueous solution (mg L−1 ), qe the adsorption amount (mg/g) at equilibrium and qm is the adsorption capacities of saturation, KL represents enthalpy of sorption and should vary with temperature, and KF and n are the Freundlich constants related to the sorption capacity and sorption intensity, respectively. The relative parameters calculated from the two models are listed in Table S1. It is shown that the equilibrium adsorption was well-described by the Langmuir isotherm mode, as shown in Fig. 7. The maximum adsorption capacity, Qmax obtained from the slope were found to be 145.35 mg/g. Comparing to Qmax value of Cr(VI) sorption on other sorbents, such as surface modified sand (6.24 mg/g) [41], Fe@Fe2 O3 nanowires (7.78 mg/g) [42], elaeagnus tree leaves (10.94 mg/g) [43], amino starch (12.12 mg/g) [44], silica matrices(18 mg/g) [45], PEI modified activated carbon (20.05 mg/g) [46]. It could be seen that MCGO-IL presents the highest adsorption capacity of today’s materials. What’s more important, there are two factors contribute to metal ion sorption on MCGO-IL: (1) the abundant oxygen-containing functional groups on the surfaces of graphene oxide and chitosan make the adjacent oxygen atoms available to bind metal ions. (2) The delocalized ␲ electron systems of graphene oxide layer can act as Lewis base to form electron donor acceptor complexes with metal ions. Strong surface complexation between the graphene oxide nanosheets and metal ions occurs through the Lewis acid base interaction.

1.6 1.4

ce/Qe

3.4. The sorption isotherm Equilibrium adsorption isotherms reflect the partitioning of the metal ion between the adsorbent and liquid phases at equilibrium as a function of concentration, so they are of prime importance in the design of adsorption systems. The Cr(VI) adsorption equilibrium was studied by using Langmuir isotherm model and Freundlich isotherm model, respectively. The linear form of the Langmuir model could be expressed as follows [39]:

1 ln ce n

1.2 1.0 0.8 0.6 40

60

80 100 120 140 160 180

ce(mg/L) Fig. 7. The Langmuir isotherm model. The concentration of MCGO-IL was 1.0 g L−1 . The contact time was 40 min. The pH 3.0. The temperature was 303 K.

L. Li et al. / International Journal of Biological Macromolecules 66 (2014) 172–178 0

Shandong Provincial Natural Science Foundation of China (No. ZR2012BM020) and the Scientific and technological development Plan Item of Jinan City in China (No. 201202088).

140 120 qe/(mg.g-1)

177

100

References

80 60 40 20 0

1

2

3

4

5

6

7

8

9

10

Cycling times Fig. 8. Adsorption amount of Cr(VI) for different cycles. The concentration of MCGOIL was 1.0 g L−1 . The initial Cr(VI) ion concentrations was 150 mg L−1 . The contact time was 60 min. The pH 3.0. The temperature was 303 K.

3.5. Regeneration of saturated adsorbents Desorption character was an important factor for evaluating potential application value of the biosorbent. Such adsorbent has higher adsorption capability as well as better desorption property which will reduce the overall cost for the adsorbent. As mentioned earlier, adsorption capacity of the MCGO-IL biosorbent was strongly affected by acidity, which offered a possibility for desorption. Thus, desorption of Cr(VI) was carried out by HCl at 25 ◦ C, and the result is shown in Fig. 8. It can be found that only a slight loss in adsorption capacity can be seen after four consecutive cycles of adsorption–desorption, suggesting the good performance and recyclability of the prepared MCGO-IL as adsorbents for Cr(VI) removal. And then the uptake capacity of Cr(VI) decreased rapidly. At the tenth regeneration cycle, the adsorption capacity is about 20 mg/g. In my opinion, the adsorption capacity over 50 mg/g is relatively good, so the optimal repeated time is six. The reason for the removal efficiency decrease can be explained well: (1) the Cr(VI)-adsorbed MCGO-IL cannot completely be desorbed, (2) the Cr(VI) was partially reduced into Cr(III) by the surface hydroxyl groups on MCGO-IL, that was precipitated in the form of Cr2 O3. With the increase in Cr2 O3 remaining on the MCGO-IL, the availability of the active sites would decrease [47,48]. These results show that the adsorbents can be recycled for Cr(VI) adsorption, and the adsorbents can be reused. 4. Conclusions In summary, the MCGO-IL was synthesized by impregnating MCGO with IL. The MCGO-IL exhibited extraordinary removal capacity and fast adsorption rates for Cr(VI) removal in water due to the high surface area and the abundant functional groups of adsorbent. Mechanical strength and stability of the biosorbents were indicated to be enough for adsorption. The pseudo-secondorder kinetic model best describes the adsorption behavior of the Cr(VI) on MCGO-IL. These materials showed their highest adsorption capacity at relatively lower pH value solutions. Langmuir adsorption isotherm gave a good fit to the adsorption data with an adsorption capacity of 145.35 mg/g. The adsorbed chromium could be effectively regeneration using HCl. This ensures the process to be economical and ecofriendly. These MCGO-IL composites have great potential applications in removing metal ions from polluted water. Acknowledgements This work was supported by the National Natural Science Foundation of China (NSFC, Nos. 21345005 and 21205048), the

[1] J.O. Nriagu, J.M. Pacyna, Quantitative assessment of worldwide contamination of air, water and soils by trace metals, Nature 333 (1988) 134–139. [2] M.A. Peraza, F. Ayala-Fierro, D.S. Barber, E. Casarez, L. Rael, Effects of micronutrients on metal toxicity, Environ. Health Perspect. 106 (Suppl. 1) (1998) 203–216. [3] G.S. Shukla, R.L. Singhal, The present status of biological effects of toxic metals in the environment: lead, cadmium, and manganese, Can. J. Physiol. Pharmacol. 62 (1984) 1015–1031. [4] L.C. Hsu, S.L. Wang, Y.C. Lin, M.K. Wang, P.N. Chiang, J.C. Liu, W.H. Kuan, C.C. Chen, Y.M. Tzou, Cr(VI) removal on fungal biomass of Neurospora crassa: the importance of dissolved organic carbons derived from the biomass to Cr(VI) reduction, Environ. Sci. Technol. 44 (2010) 6202–6208. [5] J.N. Sahu, J. Acharya, B.C. Meikap, Response surface modeling and optimization of chromium(VI) removal from aqueous solution using Tamarind wood activated carbon in batch process, J. Hazard. Mater. 172 (2009) 818–825. [6] L. Monser, N. Adhoum, Modified activated carbon for the removal of copper, zinc, chromium and cyanide from wastewater, Sep. Purif. Technol. 26 (2002) 137–146. [7] N. Kongsricharoern, C. Polprasert, Chromium removal by a bipolar electrochemical precipitation process, Water Sci. Technol. 34 (1996) 109–116. [8] A. Hafez, S. El-Mariharawy, Design and performance of the two stage/to-pass RO membrane system for chromium removal from tannery wastewater: Part3, Desalination 165 (2004) 141–151. [9] Z. Modrzejewska, W. Kaminski, Separation of Cr(VI) on chitosan membranes, Ind. Eng. Chem. Res. 38 (1999) 4946–4950. [10] S. Rengaraj, C.K. Joo, Y. Kim, J. Yi, Kinetics of removal of chromium from water and electronic process wastewater by ion exchange resins: 1200H, 1500H and IRN97H, J. Hazard. Mater. 102 (2003) 257–275. [11] S. Rengaraj, K.-H. Yeon, S.-H. Moon, Removal of chromium from water and wastewater by ion exchange resins, J. Hazard. Mater. 87 (2001) 273–287. [12] Y. Zhao, J.R. Peralta-Videa, M.L. Lopez-Moreno, M. Ren, G. Saupe, J.L. GardeaTorresdey, Kinetin increases chromium absorption, modulates its distribution, and changes the activity of catalase and ascorbate peroxidase in Mexican palo verde, Environ. Sci. Technol. 45 (2011) 1082–1087. [13] B. Fonseca, H. Figueiredo, J. Rodrigues, A. Queiroz, T. Tavares, Mobility of Cr, Pb, Cd Cu and Zn in a loamy sand soil: a comparative study, Geoderma 164 (2011) 232–237. [14] X.L. Tan, M. Fang, C.L. Chen, S.M. Yu, X.K. Wang, Counterion effects of Ni2+ and sodium dodecylbenzene sulfonate adsorption to multiwalled carbon nanotubes in aqueous solution, Carbon 46 (2008) 1741–1750. [15] X.L. Tan, Q.H. Fan, X.K. Wang, B. Grambow, Eu(III) sorption to TiO2 (anatase and rutile): Batch XPS, and EXAFS study, Environ. Sci. Technol. 43 (2009) 3115–3121. [16] M. Fernández-García, A. Martínez-Arias, J.C. Hanson, J.A. Rodriguez, Nanostructured oxides in chemistry: characterization and properties, Chem. Rev. 104 (2004) 4063–4104. [17] M.S. Mauter, M. Elimelech, Environmental applications of carbon-based nanomaterials, Environ. Sci. Technol. 42 (2008) 5843–5859. [18] Q. Wang, Y. Guan, X. Liu, X. Ren, M. Yang, High-capacity adsorption of hexavalent chromium from aqueous solution using magnetic microspheres by surface dendrimer graft modification, J. Colloid Interface Sci. 375 (2012) 160–166. [19] G. Crini, Recent developments in polysaccharide-based materials used as adsorbents in wastewater treatment, Prog. Polym. Sci. 30 (2005) 38–70. [20] R.D. Rogers, Materials science reflections on ionic liquids, Nature 447 (2007) 917–918. [21] L. Alonso, A. Arce, M. Francisco, O. Rodrı´ıguez, A. Soto, Gasoline desulfurization using extraction with [C8mim][BF4] ionic liquid, AIChE J. 53 (2007) 3108–3115. [22] H.T. Liu, Y. Liu, J.H. Li, Ionic liquids in surface electrochemistry, Phys. Chem. Chem. Phys. 12 (2010) 1685–1697. [23] H. Yang, C. Shan, F. Li, D. Han, Q. Zhang, L. Niu, Covalent functionalization of polydisperse chemically-converted graphene sheets with amine-terminated ionic liquid, Chem. Commun. 45 (2009) 3880–3882. [24] S.J. Guo, S.J. Dong, E.K. Wang, Constructing carbon nanotube/Pt nanoparticle hybrids using an imidazolium-salt-based ionic liquid as a linker, Adv. Mater. 22 (2010) 1269–1272. [25] H.B. Xie, S.B. Zhang, S.H. Li, Chitin and chitosan dissolved in ionic liquids as reversible sorbents of CO2 , Green Chem. 8 (2006) 630–633. [26] P. Ramesh, S. Bhagyalakshmi, S. Sampath, Preparation and physicochemical and electrochemical characterization of exfoliated graphite oxide, J. Colloid Interface Sci. 274 (2004) 95–102. [27] Lulu Fan, Chuannan Luo*, Xiangjun Li, Fuguang Lu, Huamin Qiu, Min Sun, Fabrication of novel magnetic chitosan grafted with graphene oxide to enhance adsorption properties for methyl blue, J. Hazard. Mater. 215-216 (2012) 272–279. [28] D. Depan, B. Girase, J.S. Shah, R.D.K. Misra, Structure–process–property relationship of the polar graphene oxide-mediated cellular response and stimulated growth of osteoblasts on hybrid chitosan network structure nanocomposite scaffolds, Acta Biomater. 7 (2011) 3432–3445.

178

L. Li et al. / International Journal of Biological Macromolecules 66 (2014) 172–178

[29] A. Santhana Krishna Kumara, Timsi Guptab, S. Shruti Singh Kakanc, Kalidhasana, Manasid, N. Vidya Rajeshd, Rajesha, Effective adsorption of hexavalent chromium through a three center (3c) co-operative interaction with an ionic liquid and biopolymer, J. Hazard. Mater. 239–240 (2012) 213–224. [30] P. Srinivasa Rao, S. Sridhar, M.Y. Wey, A. Krishnaiah, Pervaporative separation of ethylene glycol/water mixtures by using crosslinked chitosan membranes, Ind. Eng. Chem. Res. 46 (2007) 2155–2163. [31] Y. Li, B. Gao, T. Wu, D. Sun, X. Li, B. Wang, F. Lu, Hexavalent chromium removal from aqueous solution by adsorption on aluminum magnesium mixed hydroxide, Water Res. 43 (2009) 3067–3075. [32] B.M. Weckhuysen, I.E. Wachs, Surface chemistry and spectroscopy of chromium in inorganic oxides, Chem. Rev. 96 (1996) 3327–3349. [33] L. Levankumar, V. Muthukumaran, M.B. Gobinath, Batch adsorption and kinetics of chromium (VI) removal from aqueous solutions by Ocimum americanum L. seedpods, J. Hazard. Mater. 161 (2009) 709–713. [34] D. Park, S.R. Lim, Y.S. Yun, J.M. Park, Development of a new Cr(VI)biosorbent from agriculture biowaste, Bioresour. Technol. 99 (2008) 8810–8818. [35] P. Suksabye, P. Thiravetyan, W. Nakbanpote, Column study of chromium(VI) adsorption from electroplating industry by coconut coir pith, J. Hazard. Mater. 160 (2008) 56–62. [36] S. Lagergren, Zur theorie der sogennanten adsorption geloster stoffe, K. Sven. Vetenskapsakad. Handl. 24 (1898) 1–39. [37] Y.S. Ho, Review of second-order models for adsorption systems, J. Hazard. Mater. B 136 (2006) 681–689. [38] L. Li, L. Fan, M. Min, H. Qiu, X. Li, H. Duan, C. Luo, Adsorbent for chromium removal based on graphene oxide functionalized with magnetic cyclodextrinchitosan, Colloids Surf. B: Biointerf. 107 (2013) 76–83.

[39] I. Langmuir, The constitution and fundament properties of solids and liquids: Part 1. Solids, J. Am. Chem. Soc. 38 (1916) 2221–2295. [40] H. Freundlich, Colloid and Capillary, E.P. Dutton and Co., New York, 1928. [41] S.M. Lee, W.G. Kim, C. Laldawngliana, D. Tiwari, Removal behavior of surface modified sand for Cd (II) and Cr (VI) from aqueous solutions, J. Chem. Eng. Data 55 (2010) 3089–3094. [42] Z. Ai, Y. Cheng, L. Zhang, J. Qiu, Efficient removal of Cr (VI) from aqueous solution with Fe@ Fe2 O3 core−shell nanowires, Environ. Sci. Technol. 42 (2008) 6955–6960. [43] J. Zolgharnein, A. Shahmoradi, Adsorption of Cr (VI) onto elaeagnus tree leaves: statistical optimization, equilibrium modeling, and kinetic studies, J. Chem. Eng. Data 55 (2010) 3428–3437. [44] A. Dong, J. Xie, W. Wang, L. Yu, Q. Liu, Y. Yin, A novel method for amino starch preparation and its adsorption for Cu(II) and Cr(VI), J. Hazard. Mater. 181 (2010) 448–454. [45] G. Solange Alvarez, M.L. María Lucía Foglia, D.E. Camporotondi, et al., A functional material that combines the Cr(VI) reduction activity of Burkholderia sp. with the adsorbent capacity of sol–gel materials, J. Mater. Chem. 21 (2011) 6359–6364. [46] M. Owlad, M.K. Aroua, W.M.A.W. Daud, Hexavalent chromium adsorption on impregnated palm shell activated carbon with polyethyleneimine, Bioresour. Technol. 101 (2010) 5098–5103. [47] N. Wu, H. Wei, L. Zhang, Efficient removal of heavy metal ions with biopolymer template synthesized mesoporous titania beads of hundreds of micrometers size, Environ. Sci. Technol. 46 (2012) 419–425. [48] J. Fang, Z.M. Gu, D.C. Gang, C.X. Liu, E.S. Ilton, B.L. Deng, Cr(VI) removal from aqueous solution by activated carbon coated with quaternized poly(4vinylpyridine), Environ. Sci. Technol. 41 (2007) 4748–4753.

graphene oxide composite and application for water treatment.

Magnetic chitosan and graphene oxide-ionic liquid (MCGO-IL) composites as biodegradable biosorbents were synthesized by impregnating MCGO with ionic l...
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