zeolite electrospun composite nanofibrous membrane for adsorption of Cr6+, Fe3+ and Ni2+

Journal of Hazardous Materials 322 (2017) 182–194

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Chitosan/(polyvinyl alcohol)/zeolite electrospun composite nanofibrous membrane for adsorption of Cr6+ , Fe3+ and Ni2+ Umma Habiba, Amalina M. Afifi, Areisman Salleh, Bee Chin Ang ∗ Center of Advanced Material, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia

h i g h l i g h t s

g r a p h i c a l

a b s t r a c t

• Chitosan/PVA/zeolite

•

•

• •

nanofibrous composite membrane was prepared by electrospinning method as a new chitosan based composite membrane. The notable property of the resulting nanofibrous composite membrane is the rigidity and no weight loss in distilled water, basic and acidic medium. Heavy metal removal effectiveness reaches to almost 100%, as the initial concentration of heavy metal is 10–20 mg/L. The kinetic rate of adsorption is very high. The reusability of the chitosan/PVA/zeolite nanofibrous membrane is an important finding of the current study.

a r t i c l e

i n f o

Article history: Received 4 November 2015 Received in revised form 4 June 2016 Accepted 12 June 2016 Available online 30 June 2016 Keywords: Adsorption Chitosan Electrospinning Heavy metal Morphology study and zeolite

∗ Corresponding author. E-mail address: [email protected] (B.C. Ang). http://dx.doi.org/10.1016/j.jhazmat.2016.06.028 0304-3894/© 2016 Elsevier B.V. All rights reserved.

a b s t r a c t In this study, chitosan/polyvinyl alcohol (PVA)/zeolite nanofibrous composite membrane was fabricated via electrospinning. First, crude chitosan was hydrolyzed with NaOH for 24 h. Afterward, hydrolyzed chitosan solution was blended with aqueous PVA solution in different weight ratios. Morphological analysis of chitosan/PVA electrospun nanofiber showed a defect-free nanofiber material with 50:50 weight ratio of chitosan/PVA. Subsequently, 1 wt.% of zeolite was added to this blended solution of 50:50 chitosan/PVA. The resulting nanofiber was characterized with field emission scanning electron microscopy, X-Ray diffraction, Fourier transform infrared spectroscopy, swelling test, and adsorption test. Fine, beadfree nanofiber with homogeneous nanofiber was electrospun. The resulting membrane was stable in distilled water, acidic, and basic media in 20 days. Moreover, the adsorption ability of nanofibrous membrane was studied over Cr (VI), Fe (III), and Ni (II) ions using Langmuir isotherm. Kinetic parameters were estimated using the Lagergren first-order, pseudo-second-order, and intraparticle diffusion kinetic models. Kinetic study showed that adsorption rate was high. However, the resulting nanofiber membrane showed less adsorption capacity at high concentration. The adsorption capacity of nanofiber

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was unaltered after five recycling runs, which indicated the reusability of chitosan/PVA/zeolite nanofibrous membrane. Therefore, chitosan/PVA/zeolite nanofiber can be a useful material for water treatment at moderate concentration of heavy metals. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Nowadays, water pollution is becoming a considerable threat. Water contaminants include microorganisms, organics, heavy metals, and toxicants. Among them, heavy metals are the most dangerous because they are highly carcinogenic and cannot be decomposed or biodegraded [1]. Cr (VI) and Ni (II) are common heavy metals that can be present in water. Besides, Fe (III) is very common metal that can be present in tape water. More specifically, the main source of an appreciable iron entry into a municipal water supply is through pipeline corrosion, metal finishing and galvanized pipe manufacturing [2]. Consumption dose as low as 60 mg/kg of body weight can cause death [3]. Excessive iron in the blood can cause damage of cells of gastrointestinal tract [4]. A research study on effluent of Taloja industrial belt of Mumbai showed that Iron content was 12.8 mg/L which is very high from the acceptable value [5]. In the last few decades, some processes, such as reverse osmosis, flocculation [6], bacterial action, and adsorption [7], have been used. Among them, adsorption is the most satisfactory because of its simple design, low initial cost, and manageable operation. Nevertheless, adsorbent materials tend to aggregate after adsorption [8]. In any adsorption process, one common difficulty is adsorbent regeneration. Typically, chemical, ultrasonic, and thermal methods are used for adsorbent regeneration [9,10]. However, these methods have several limitations, such as high temperature requirement, unreasonable burnout of the adsorbent, pollution of the adsorbent by inorganic chemicals or organic solvents [10], and adsorbent material separation. The current improvement in nanotechnology can offer solutions to overcome the present problems in existing water treatment process. In recent years, electrospun nanofiber membrane is attracting the attention of researchers. Electrospun nanofibrous membrane offers promising properties, such as porosity, tunable pore size, and high surface to volume ratio, which make the membrane a suitable material for adsorption of heavy metal from water [11]. Nevertheless, insufficient hydrophilicity [12], high swelling rate [13], low mechanical strength [14], membrane fouling, cake or gel layer formation [15], and pore blocking by adsorption of solute on pore walls [16] are some difficulties of nanofiber membrane. Moreover, commercially available membranes are non-biodegradable. Chitosan is a biodegradable polymer. With its polycationic nature, chitosan is widely used for water treatment because it can bind heavy metal ions. Nonetheless, it is mechanically unstable, pH sensitive, and susceptible to swelling [17]. Chitosan-based electrospun nanofiber has several drawbacks, such as decreasing adsorption capacity after several run [18] and slow adsorption rate and swelling [18,19]. Previously, polyvinyl alcohol (PVA) was used to immobilize chitosan [20]. PVA reduces the crystallinity of chitosan network to some extent [21]. The strong hydrogen bond of PVA with functional group NH2 and NH–R causes the formation of good nanofiber during electrospinning [22]. However, slow heavy metal adsorption rate was reported for chitosan/PVA electrospun nanofiber [23]. The filler incorporated in this electrospun membrane was zeolite. Where, zeolite is a widely used adsorbent for removal of heavy metal ions. Zeolite structure is mainly composed of three com-

ponents: aluminosilicate framework, exchangeable cations, and water within the pores. The porous structure of zeolite can accommodate heavy metal ions. The exchangeable cations are also an important factor for heavy metal adsorption [24]. Nonetheless, they tend to aggregate during operation [25]. In the present study, chitosan/PVA/zeolite nanofibrous composite membrane was synthesized via electrospinning to overcome the limitation of both chitosan and zeolite. Resulting composite nanofibrous membrane was considered strengthened by zeolite to avoid swelling during operation. The combination of the functional groups of chitosan and porous frame of zeolite structure should ensure fast removal of Cr (VI), Fe (III), and Ni (II). 2. Experimental 2.1. Materials Chitosan (Mw = 8.96 × 105 g/mole, degree of deacetylation (DDA) = 40%) was obtained from SE Chemical Co. Ltd. PVA (Mw = 60000, degree of hydrolysis = 89%) and NaOH were purchased from Kuraray Co. Ltd. (Tokyo, Japan) and System, respectively. Acetic acid, FeCl3 ·6H2 O, NiCl2 ·6H2 O, zeolite, and K2 Cr2 O7 were purchased from Sigma-Aldrich. 2.2. Methodology Experimental work was divided into two major parts. It was: hydrolysis of chitosan with NaOH, and preparation of chitosan/PVA and chitosan/PVA/zeolite electrospun nanofibrous membrane. 2.2.1. Hydrolysis of chitosan The DDA of chitosan indicates the extent of transformation of N-acetyl-d-glucosamine to D-glucosamine [26]. The molecular weight and DDA of supplied chitosan were not suitable for electrospinning. Low molecular weight aligns effectively in the electromagnetic field of the electrospinning unit. Hydrolysis of chitosan causes chitosan deacetylation, which means that it increases the DDA and concurrently decreases molecular weight [27]. Furthermore, a DDA higher than 70% is needed for the solubility of chitosan [28]. Therefore, hydrolysis was performed to increase the DDA and decrease the molecular weight of chitosan. First, 40 g of NaOH was added to 80 g of distilled water. Subsequently, 2.5 wt.% of chitosan was added to the solution. The solution was stirred for 24 h at 90 ◦ C. Afterward, the samples were filtered and washed by distilled water. Finally, the filtered chitosan powders were dried in an oven at 60 ◦ C for about 7 h. 2.2.2. Preparation of chitosan/PVA and chitosan/PVA/zeolite electrospun nanofibrous membrane 2.2.2.1. Solution preparation. Approximately 7 wt.% of chitosan was dissolved in concentrated acetic acid. Chitosan solution was mixed with aqueous PVA solution in a weight ratio of 50:50, 60:40, 70:30, 80:20, and 90:10. Correspondingly, these blended solutions were numbered as A1 , A2 , A3 , A4 , and A5 . Previous study reported that chitosan/PVA can be electrospun with 30:70 weight ratio [29]. In the present study, the first composition of blend solution used was

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Adding 1 wt.% of zeolite

Preparing 50:50 of chitosan/PVA solution

Y

Stirring, room temperature Loading in 10 ml syringe

Electrospinning at feed rate of 0.2 mL/h and 10kV

Maintaining in GA vapor for 24 h

Final product

Characterization

Application Test

Adsorption of Cr (VI), Ni (II), and Fe (III) Surface morphological analysis

FTIR analysis

XRD analysis

Swelling test

Fig. 1. Flowchart of the electrospinning process of chitosan/PVA/zeolite nanofiber.

pump NE-300 (New Era Pump Systems, NY, USA), and stationary collector. Electrospinning of A1 , A2 , A3 , A4 , and A5 solutions were performed under the following conditions: 19 gauge needles, 10cm tip to collector distance, 0.1–0.4 mL h−1 feed rate, 7.1–14 kV voltage. The 50:50 of chitosan/PVA ratio was used for zeolite addition because of its defect-free morphology, which is shown in the result and discussion section. About 1 wt.% of zeolite was stirred with 50:50 of chitosan/PVA. Finally, electrospinning was performed under the following conditions: 19 gauge needle, 10-cm tip to collector distance, 0.4 mL h−1 feed rate, and 10 kV applied voltage. The electrospun fibers were kept in desiccator with glutaraldehyde vapor for 24 h. The flowchart of the process is shown in Fig. 1. 2.3. Characterization

Fig. 2. Fourier transform infrared (FTIR) spectra of crude and hydrolyzed chitosan.

50:50 to ensure large amount of biopolymer, which is the chitosan content in the resulting nanofiber. 2.2.2.2. Electrospinning. Electrospinning setup consisted of a highvoltage power supply 25 kV (LD Didactic GmbH, Germany), syringe

2.3.1. Fourier transform infrared (FTIR) analysis FTIR spectroscopy was used to determine the DDA of chitosan after hydrolysis and bonding among chitosan/PVA/zeolite membrane materials. This method was performed using Nicolet iS10 FTIR spectrometer from Thermo Scientific. The spectral range was 600–3000 wavenumber with a resolution of 4 cm−1 . 2.3.2. Field-emission scanning electron microscopy (FESEM) analysis The morphology of chitosan/PVA nanofiber was observed by field emission scanning electron spectroscopy (ZEISS AURIGA). However, the morphology of chitosan/PVA/zeolite nanofibrous

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Fig. 3. Field emission scanning electron microscopy (FESEM) image of nanofiber membrane and fiber diameter distribution of polymer blends.

membrane was studied under FESEM (High-resolution FEI Quanta 200F; Hitachi; Japan).

˚ operated at 45 kV, 40 mA, a step size of 0.026◦ , and (␭=1.54056 A), a scanning rate of 0.1◦ s−1 over a 2␪ range of 5◦ –100◦ .

2.3.3. X-ray diffraction (XRD) analysis of chitosan/PVA/zeolite nanofibrous membrane XRD analysis was conducted to determine the overall crystallinity of the nanofibrous composite membrane. The XRD patterns of the powder and composite were obtained using PANanalytical Empyrean XRD (USA) with monochromated CuK radiation

2.3.4. Swelling experiments The swelling behavior of the resulting nanofiber was necessary to determine the durability of fiber in water. In this study, distilled water (pH = 7), acidic (pH = 3), and basic media (pH = 10) were used for the swelling test. Chitosan/PVA/zeolite membrane samples were weighted and subsequently immersed in distilled water, acidic, and basic media for 20 days. The swollen samples

Table 1 Applied voltage and mean diameter of the blended solutions. Sample Name

Product Type

Voltage (kV)

Flow Rate (mL h−1 )

SD%

MD (nm)

A1 A2 A3 A4 A5

Fibers Fibers Fibers Particles Particles

7.1 9.1 9.8 12 12

0.40 0.30 0.25 0.1 0.1

28.50 52.94 62.50

59 85 88

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Fig. 4. FESEM image of chitosan/PVA/zeolite nanofiber and fiber diameter distribution.

Fig. 5. Mapping analysis showing the elemental topographical distribution of carbon, oxygen, silicon, sodium, and aluminum.

were weighted immediately after the excess water was removed. The swelling ratio (Sw ) was estimated using the following equation: SW =

Ws − Wd Wd

(1)

where Wd and Ws are the masses before and after dipping in water, respectively. 2.3.5. Adsorption study The adsorption behavior of chitosan/PVA/zeolite nanofibrous membrane was evaluated on Cr (VI), Fe (III), and Ni (II). About

0.1 g of the membrane was agitated with 10 mL of potassium (VI) dichromate, nickel (II) chloride, and iron (III) chloride solution by using a magnetic stirrer. The initial concentration of heavy metal ion varied within 0.02–1 mmol/L. Solution concentration was calculated after different time intervals. Stirring was performed to ensure the maximum contact of fiber surface with the metal ions present in the solution. Concentration of the solution was measured by using flame atomic absorption spectrometer (Analyst 400, Perkin Elmer).

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Fig. 6. X-ray diffraction (XRD) spectra of zeolite and chitosan/PVA/zeolite nanofibrous composite membrane.

Fig. 7. FTIR spectra for (a) PVA nanofiber, (b) chitosan, (c) chitosan/PVA nanofiber, and (d) chitosan/PVA/zeolite nanofiber.

The adsorption of heavy metals by the adsorbent was calculated by using the following formula [30]: qt =

(Co − Ct ) V m

3. Results and discussion 3.1. Hydrolysis of chitosan

(2)

where C0 and Ct are the initial and equilibrium concentrations of heavy metal ion solution (mmol/L), respectively, V is the volume of solution (L), and m is the weight of composite film (g).

3.1.1. FTIR analysis of hydrolyzed chitosan The FTIR spectrum of resulting chitosan is shown in Fig. 2. The presence of saccharide group was confirmed by the absorption observed at 894, 1080, and 1150 cm−1 [27]. Absorption band

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Table 2 Comparison of the characteristic peak positions of zeolite and chitosan/polyvinyl alcohol (PVA)/zeolite nanofibrous composite membrane. No.

[h k l]

2␪ position (pure zeolite)

2␪ position (nanofiber membrane)

Change in 2␪ position

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21

001 111 012 022 003 123 014 224 234 334 344 226 037 047 356 555 338 556 139 010

7.05 12.3 15.9 20.3 21.5 26.9 29.8 35.6 39.2 42.7 47.2 48.9 56.3 60 62.6 65 68 70.4 72 77

8.85 11.65 14.9 19.3 20.65 26.4 28.8 35.2 38.7 42.5 46.8 47.9 56 60 62.5 65 68 69.8 72 76.7

1.8 0.65 1.0 1.0 0.8 0.5 1.0 0.4 0.5 0.2 0.4 1.0 0.3 0 0.1 0 0 0.6 0 0.3

Fig. 8. (a) Lagergren first-order model, (b) pseudo-second-order kinetics, and (c) intra-particle diffusion models.

at 1590 and 1653 cm−1 indicated the presence of NH2 and C O NHR, respectively, where 3363 cm−1 indicated the N H stretch [27]. The result showed that the chemical backbone of chi-

tosan was not damaged after hydrolysis. The intensity of 1651 cm−1 was shifted to 1653 cm−1 with low intensity, whereas the peak intensity of 1578 cm−1 was increased with shifting to 1591 cm−1 .

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Table 3 Parameters of kinetic models. M+

6+

Cr Fe3+ Ni2+

qe ,exp (mmol/g)

0.09 0.08 0.083

Lagergren first order constant

Pseudo second order constant

qe.cal (mmol/g)

k1 (min−1 )

R2

qe.cal (mmol/g)

k2 (g/mmol min)

R2

kid (mmol/g min1/2 )

R2

0.68 0.23 0.11

0.67 0.624 0.867

0.85 0.99 0.97

0.09 0.17 0.5

102 0.35 0.11

0.99 0.5 0.7

0.009 0.06 0.066

0.96 0.98 0.99

Table 4 Langmuir isotherm parameters obtained by using linear method.

3.2. Fabrication of chitosan/PVA nanofibrous composite membrane

Heavy Metal

qm (mmol/g)

Ka (L/mmol)

R2

Cr (VI) Fe (III) Ni (II)

0.17 0.11 0.03

1.34 0.57 14.57

0.97 0.99 0.99

This result indicated the deacetylation of chitosan molecule after hydrolysis [31]. Therefore, new NH2 groups were produced.

3.1.2. Calculation of the DDA Several absorption band ratios, such as A1655 /A2875 , A1655 /A3450 , A1320 /A3450 , A1655 /A1030 , A1560 /A897 , and A1320 /A1420 can be used to determine the DDA [32]. However, in the present study, the ratio of A1320 and A1420 was selected for the determination of DDA. The DDA was calculated using the following equations [33]: DA% = 31.92

Intra particle mass transfer diffusion constant

A1320 − 12.20 A1420

DD% = 1 − DA%

(3)

3.2.1. Morphology study Fig. 3 shows the FESEM micrographs of nanofibrous membrane. Defect-free nanofiber was obtained from the electrospinning of A1 solution. Irregular shape and beads were observed in the nanofibrous material of A2 and A3 , respectively. Furthermore, polymer blends A4 and A5 formed particles only. The instability of jet, low molecular weight, high applied voltage, low viscosity, and high surface tension are some reasons of bead formation in nanofiber [27,33,36]. Referring to Table 1, the applied voltages for A2 , A3 , A4 , and A5 were higher than that of A1 , which might be the reason for the formation of particles with increasing chitosan content in the polymer blend. Fiber diameter was measured via Digimizer, and the size distribution histogram was drawn. Fig. 3 shows that the mean diameter and standard deviation increased with increasing chitosan content in polymer blend. This observation can be attributed to the fact that the amino group of chitosan was protonated in the solution, which caused the viscous solution, and high voltage was required to obtain the stretched jet [37]. As reported by Huang et al. (2003), higher voltage results in larger diameter. Therefore, 50:50 of chitosan/PVA had the most suitable mean diameter and standard deviation.

(4)

where DD% = DDA DA% = Degree of Acetylation This A1320 /A1420 ratio was used for this calculation because it is sensitive to the chemical composition of chitin and chitosan [33]. The DDA calculated using the FTIR spectra is 84% for 24-h hydrolysis. Thus, 84% of the total chitosan is D-glucosamine units [34]. Therefore, the amount of free amino groups was increased. NH2 is an important functional group of chitosan that functions as active sites in different reactions and bonding for removal of pollutants from wastewater [35].

3.3. Fabrication of chitosan/PVA/zeolite nanofibrous composite membrane 3.3.1. Electrospinning The applied voltage required for electrospinning of chitosan/PVA/zeolite blend solution was 10 kV. The addition of filler material increases the viscosity and viscoelastic force [38]. Higher viscoelastic force causes the higher resistance toward electrostatic force that stretches the jet. Hence, high voltage was needed to continue the electrospinning process.

Table 5 Comparison of adsorption capacity and kinetic rate. Heavy Metal

Adsorbent Material

Rate Constant, k

qmax (mmol/g)

Reference

Cr (VI)

Bifunctionalized chitosan Chitosan/MWCNT/Fe3 O4 Chitosan/graphene oxide composite nanofibrous Fe-crosslinked chitosan complex Modified magnetic chitosan chelating resin Chitosan/PVA/zeolite nanofibrous membrane Natural zeolite Ethylenediamine-modified multiwalled carbon nanotubes Phosphorylated Orange Waste Chelating resin Mn3 O4 /TiO2 composite nanosheets Chitosan/PVA/zeolite nanofibrous membrane Electrospun nanofiber membrane of PEO/Chitosan Chitosan/calcium alginate Chitosan/silica Chitosan/clinoptilolite Bifunctionalized chitosan nanofibrous membrane Chitosan/PVA/zeolite

0.052 ± 0.28 0.095 0.02 0.364 0.018 102 0.0449 N/A N/A N/A N/A 0.624 0.02638 0.033 0.02 0.004 0.0062 ± 0.24 0.867

N/A 6.45 5.5 9.85 1.12 0.17 0.13 0.51 3.06 0.33 1.25 0.11 5.7 3.78 4.33 4.2 N/A 0.03

[65] [66] [67] [68] [69] Currents study [70] [71] [72] [73] [74] Currents study [18] [75] [75] [76] [65] Currents study

Fe (III)

Ni (II)

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Fig. 9. Langmuir plot for adsorption of Cr (VI), Fe (III), and Ni (II).

3.3.2. Characterization 3.3.2.1. Morphology study. FESEM image and fiber diameter distribution are shown in Fig. 4. Zeolite particles were embedded into the nanofiber. Particles were uniformly distributed over the nanofiber surface. The strong interaction of zeolite with the functional group of chitosan and PVA was considered the reason of uniform particle distribution. This behavior was also considered the reason of formation of rough and porous surface [38]. However, higher viscoelastic force causes the higher resistance toward electrostatic force that stretches the jet. This effect magnifies the fiber diameter at high filler concentrations. A total of 100 fibers were analyzed with Digimizer, and the size distribution histogram was drawn. Fig. 4 shows the respective fiber diameter distribution of the nanofiber. The comparison between nanofiber with and without zeolite was also presented. The mean diameter was increased from 59 nm to 70 nm. However, the standard deviation was decreased from 28.5% to 19%. This results supported the homogeneity of chitosan/PVA/zeolite membrane. The inorganic filler increases the viscosity and viscoelastic force, which hamper the surface tension of the chitosan solution to be electrospun [38]. Consequently, the bead formation decreases, and the fiber diameter distribution becomes uniform [39]. Fig. 5 shows the mapping results of chitosan/PVA/zeolite nanofiber. The results revealed the uniform distribution of zeolite particles in the membrane. Therefore, zeolite particles were scattered through the fiber interior and outer surfaces. In addition, the

particle in the outer surface can ensure surface roughness, which leads to the high hydrophilicity of membrane [40,41]. 3.3.2.2. XRD analysis. Fig. 6 shows the XRD patterns of chitosan/PVA/zeolite membrane. A comparison between the peaks of zeolite and chitosan/PVA/zeolite membrane is shown in Table 2. Some zeolite peaks were changed after incorporation with membrane. The limitation in zeolite crystallization is caused by the strong interaction between chitosan and zeolite [42]. Moreover, the chitosan peaks around 10◦ and 20◦ became weak in the composites representing strong interaction among chitosan, PVA, and filler materials, as well as loosing of crystallinity [43]. Thus, the XRD results proved the interaction among chitosan, PVA, and zeolite. 3.3.2.3. FTIR analysis of chitosan/PVA/zeolite nanofibrous membrane. The FTIR spectra of nanofiber membrane are shown in Fig. 7. The absorption peak at 1257 cm−1 was assigned to the O H band [44] of PVA shifted to 1260 cm−1 with low frequency for chitosan/PVA nanofiber. The 1375 cm−1 peak was the characteristic peak of CH2 connecting to the OH group, which was present in the spectra of PVA, chitosan, and chitosan/PVA. This peak became weak in the chitosan/PVA/zeolite because of vibration limitation [45]. Hence, the interaction of zeolite with chitosan occurred over the O H groups. The characteristic peak of the primary amino of chitosan was observed at 1650 cm−1 , which became weak in chitosan/PVA and chitosan/PVA/zeolite membrane because of the H-bonds. Some

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common peaks in the range of 1000–1200 cm−1 were the characteristic peaks of C O vibration of chitosan and PVA molecule [46]. These bands overlapped with the band of T–O stretching vibration of zeolite in the resulting membrane [47]. The 1432 and 1420 cm−1 peaks were the characteristic peaks of C H wagging vibration in PVA and chitosan, respectively [48]. The 1591 cm−1 peak was assigned to the secondary amino in chitosan molecule [46]. Shifting to lower frequency with significant increase in peak intensity was observed at 1420 and 1592 cm−1 in the composite membrane. The peak at 660 cm−1 was the crystalline-sensitive band of chitosan [49], which disappeared in the composite because of the hydrogen bonding of chitosan with acetic acid and PVA. This result implied that chitosan lost its crystallinity to some extent, which was also confirmed by XRD analysis. After dissolving the chitosan in acetic acid, the intensity of 1591 cm−1 was increased, which indicated the further deacetylation of chitosan molecule in the acidic acid [31]. Therefore, new NH2 groups were produced. The 1591 cm−1 peak intensity was decreased in chitosan/PVA and resulting composite membrane. Hydrogen bonding decreases the frequency of stretching vibration, thereby implying formation of hydrogen bonds of chitosan, PVA, and zeolite via NH2 . Thus, FTIR results provided evidence to the XRD results that some interactions had occurred among the components. The weak interaction between composite matrix and filler materials causes the poor mechanical strength [50]. Therefore, strong interaction among chitosan, PVA, and zeolite will show good mechanical strength and long lifespan. 3.3.2.4. Swelling test. Swelling test of chitosan/zeolite composite nanofiber was carried out for 20 days in distilled water, basic, and acidic media. All media showed no weight change. Several factors can be responsible for this behavior, such as insolubility of chitosan fraction [51]; hydrogen bonding interactions among chitosan, PVA, and zeolite; low DDA [49]; and crystallinity of the membrane [42]. Moreover, no aggregation was observed. The rigidity and shape of the nanofibrous membrane were unaltered after immersion in distilled water and basic medium. However, shrinkage was observed after immersion in acidic medium. Shrinkage of chitosan/PVA/zeolite nanofibrous membrane may be caused by the decrease in the internal pore size [52]. 3.3.3. Adsorption study 3.3.3.1. Adsorption kinetics. The interaction between heavy metal and surfaces of the adsorbent material can be estimated by studying its adsorption kinetics. Lagergren first-order, pseudo-second-order, and intraparticle mass transfer diffusion models were used to investigate the kinetics of adsorption. The linear forms of these three models are shown in Eqs. (2)–(4), respectively [53]. log (qe − qt ) = logqe −

k1 t 2.303

(5)

t 1 t = + qt qe k2 q2e

(6)

qt = kid t 1/2 + c

(7)

where qe and qt are the masses of heavy metal ions adsorbed per unit mass (mg/g) of the sorbent at equilibrium and contact time t (min), respectively; k1 (min−1 ) and k2 (g/mmol. min) are the rate constants of the Lagergren first-order model and pseudosecond-order model, respectively; and kid (mmol/·g·min1/2 ) is the intraparticle diffusion rate constant. The rate constants were calculated to study the adsorption mechanism. Fig. 8 shows the linear plot of log (qe –qt ) versus t, t/qt versus t, and qt versus t1/2 for Cr (VI), Fe (III), and Ni (II). Table 3 summarizes the kinetic parameters and correlation coefficients (R2 ). The pseudo-second-order kinetic model described the adsorption kinetics of Cr (VI). Adsorption kinetics for Cr (VI) is controlled by

Fig. 10. Effect of initial concentration of heavy metal on (a) adsorption capacity (qe ) and (b) removal percentage.

the rate of direct adsorption [54]. Thus, chemical adsorption is controlled by the significant sharing or exchange of electrons between the adsorbent and adsorbate [55]. In addition, the Fe (III) and Ni (II) adsorption follows the Lagergren first-order model. Adsorption rate is an important factor in designing an adsorption system [56]. Referring to Table 3 and 5, the values of kinetic rate (k) are high, relative to other studies. Therefore, heavy metal ions were adsorbed at high energy-specific surface sites [57]. High specific interaction can be ensured between adsorbent and adsorbate in the presence of some specific cations [57]. Zeolite contains exchangeable cations. In the present study, the presence of zeolite in a nanofiber may play a significant role to increase the rate of adsorption. The high correlation coefficient value of intraparticle diffusion model indicated that pore diffusion occurred during adsorption [58]. The plot of qt against t1/2 did not pass through the origin, which implied that the adsorption process is partially governed by intraparticle diffusion [59]. 3.3.3.2. Removal mechanism. Adsorption isotherm studies are used to predict the interaction between the adsorbate, such as dye molecule or heavy metal ions and the adsorbent materials. Several adsorption isotherms can be used to determine the adsorption process. In this study, the standard isotherm, such as Langmuir

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Fig. 11. Contact time vs. concentration of heavy metal ions.

isotherms, was used. The mathematical expression of the Langmuir isotherm equation [60] is given as follows:

where qe (mmol/g) is the amount of heavy metal ions adsorbed per unit mass of adsorbent, Ce (mmol/L) is the concentration of the remaining heavy metal ions in the solution at equilibrium, qm is the maximum amount of heavy metal ions adsorbed per unit mass of adsorbent, and Ka (L/mmol) is a constant related to the affinity of the binding sites. Langmuir isotherm parameters obtained by using the linear method are listed in Table 4. The Langmuir isotherm of chitosan/PVA/zeolite nanofibrous membrane for the adsorption of Cr (VI), Fe (III), and Ni (II) is shown in Fig. 9. Close proximity was observed on the unity of correlation coefficients for the adsorption of Cr (VI), Fe (III), and Ni (II). Hence, Langmuir isotherm was the most suitable for the absorption of Cr (VI), Fe (III), and Ni (II) onto chitosan/PVA/zeolite nanofibrous membrane. The results confirmed the monolayer adsorption process of Cr (VI), Fe (III), and Ni (II) onto the resulting membrane [61].

at 0.2 mmol/L, and the lowest was 50% at 1.43 mmol/L. The graph shows that the adsorption efficiency started to drop after reaching 1 mmol/L, which showed the limit of this nanofibrous membrane in terms of adsorption capability. In the case of Ni (II), the maximum removal rate was 100% (0.02 mmol/g) at 0.2 mmol/L, and the lowest was 21% at 1.45 mmol/L. A sudden drop was also observed at around 1 mmol/L, which might be the limit of this nanofibrous membrane. Results showed that the adsorption capacity of different metal ions decreased in order of Cr (VI)
3.3.3.3. Effect of initial concentration. Fig. 10 shows the effect of the initial concentration of heavy metal on the adsorption capacity of chitosan/PVA/zeolite nanofibrous membrane. The removal percentage of heavy metal ions decreased with the increase in the initial concentration of heavy metal ions. Such result can be attributed to the fact that the adsorption sites on the chitosan/PVA/zeolite nanofiber are decreased at high heavy metal concentration [60]. The maximum removal of Cr (VI) was 100% (0.04 mmol/g) at 0.4 mmol/L, and the lowest was 93% at 1.5 mmol/L. Therefore, the highly favorable active sites were involved in the removal process of Cr (VI). This behavior implied that Cr has strong affinity to the surface of chitosan/PVA/zeolite nanofiber [62]. The maximum removal of Fe (III) was 99% (0.019 mmol/g)

3.3.3.4. Effect of contact time. Fig. 11 shows the relation between contact time and metal ion concentration. The initial heavy metal ion concentration was 1 mmol/L. The required time for maximum adsorption was small, which was in accordance with the kinetic study. The highly favorable active sites were involved in the removal process. The removal process can be attributed to both ion exchange process and direct adsorption on the surface [24]. After maximum adsorption, desorption was observed. Probable reason of desorption was the weak bond of ions to the membrane surface. The adsorption of heavy metal ions on chitosan can be obtained through different mechanisms, such as chelation, ion exchange, and electrostatic attraction [64]. The electrostatic interaction between

qe =

qm ka Ce 1 + ka Ce

(8)

The linear form of Eq. (7) is written as follows: Ce Ce 1 = + qe qm ka qm

(9)

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193

Acknowledgements The author would like to thank the financial support of the University of Malaya Research (Grant RP034C-15AET), Fundamental Research Grant Scheme (FRGS-FP048-2013B), Post-graduate Research Fund (PG048-2013B), and Ministry of Higher Education Malaysia through High-Impact Research GrantUM.C/625/1/HIR/MOHE/ENG 40.

References

Fig. 12. Cycling runs of heavy metal ion adsorption by chitosan/PVA/zeolite nanofibrous membrane.

chitosan metal ions may be influenced by the DDA and distribution of acetyl groups of chitosan [64]. Exchangeable cations of zeolite may weaken the interaction between chitosan and metal ions with increasing contact time, thereby promoting desorption. Nevertheless, further research can be conducted on this phenomenon. 3.3.3.5. Reusability test. In view of practical application, the adsorbent should be chemically stable after several repeated adsorption treatments. Therefore, the adsorption experiment was repeated five times to investigate the reusability of chitosan/PVA/zeolite. For each run, the initial heavy metal ion concentration was 1 mmol/L. Procedure of reusability test was adopted from literature [53]. After each adsorption test, the chitosan/PVA/zeolite nanofibrous membrane was soaked in distilled water for few hours. Then it was washed with distilled water and dried in room temperature. Fig. 12 shows that after five cycle adsorption experiments, chitosan/PVA/zeolite nanofibrous membrane did not show any reduction on its adsorption efficiency. Therefore, chitosan/PVA/zeolite membrane is stable under the experimental process and shows excellent reusability, which is a key factor in practical application. 4. Conclusion In this study, chitosan/PVA/zeolite electrospun nanofibrous composite membrane was successfully fabricated via electrospinning process. The composite nanofibrous membrane was characterized with FESEM, XRD, FTIR spectroscopy, swelling test, and adsorption test. The adsorption capacity of composite nanofiber was studied over Cr (VI), Fe (III), and Ni (II) ions in different time points and initial concentrations. The resulting membrane showed stability in distilled water, acidic, and basic media in 20day swelling experiment. Equilibrium isotherm data fitted well with Langmuir isotherm data. The Cr (VI) adsorption can be well described by the pseudo-second-order kinetic model. Furthermore, the adsorption of Fe (III) and Ni (II) was well described by Lagergren first-order model. Notably, the adsorption rate was high. However, the resulting nanofiber membrane showed less adsorption capacity at high concentration. The result also showed the efficient desorption, which will be further studied in future work. The adsorption capacity of the nanofiber was unaltered after five runs. This phenomenon ensures the reusability of membrane.

[1] R. Wuana, F. Okieimen, J. Imborvungu, Removal of heavy metals from a contaminated soil using organic chelating acids, Int. J. Environ. Sci. Technol. 7 (2010) 485–496. [2] J.D. Zuane, Handbook of Drinking Water Quality: Standards and Controls, Van Nostrand Reinhold, New York, 1990. [3] M. El-Harbawi, A. Sabidi, E. Kamarudin, A. Hamid, S.B. Harun, A.B. Nazlan, C. Yi, Design of a portable dual purposes water filter system, J. Eng. Sci. Technol. 5 (2010) 165–175. [4] J.-M. Sieliechi, G.J. Kayem, I. Sandu, Effect of water treatment residuals (aluminum and iron ions) on human health and drinking water distribution systems, Int. J. Conserv. Sci. 1 (2010) 175–182. [5] R.S. Lokhande, P.U. Singare, D.S. Pimple, Toxicity study of heavy metals pollutants in waste water effluent samples collected from Taloja Industrial Estate of Mumbai, India, Resour. Environ. 1 (2011) 13–19. [6] V. Golob, A. Vinder, M. Simoniˇc, Efficiency of the coagulation/flocculation method for the treatment of dyebath effluents, Dyes Pigm. 67 (2005) 93–97. [7] G. Annadurai, L.Y. Ling, J.-F. Lee, Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis, J. Hazard. Mater. 152 (2008) 337–346. [8] S.-T. Yang, Y. Chang, H. Wang, G. Liu, S. Chen, Y. Wang, Y. Liu, A. Cao, Folding/aggregation of graphene oxide and its application in Cu 2+ removal, J. Colloid Interface Sci. 351 (2010) 122–127. [9] S.U. Rege, R.T. Yang, C.A. Cain, Desorption by ultrasound: phenol on activated carbon and polymeric resin, AICHE J. 44 (7) (1998) 1519–1528. [10] M. Breitbach, D. Bathen, Influence of ultrasound on adsorption processes, Ultrason. Sonochem. 8 (2001) 277–283. [11] Z.-M. Huang, Y.-Z. Zhang, M. Kotaki, S. Ramakrishna, A review on polymer nanofibers by electrospinning and their applications in nanocomposites, Compos. Sci. Technol. 63 (2003) 2223–2253. [12] L.-L. Hwang, J.-C. Chen, M.-Y. Wey, The properties and filtration efficiency of activated carbon polymer composite membranes for the removal of humic acid, Desalination 313 (2013) 166–175. [13] L. Martinova, D. Lubasova, Electrospun chitosan based nanofibers, Res. J. Text. Appar. 12 (2008) 72–79. [14] K. Desai, K. Kit, J. Li, P.M. Davidson, S. Zivanovic, H. Meyer, Nanofibrous chitosan non-wovens for filtration applications, Polymer 50 (2009) 3661–3669. [15] S. Homaeigohar, J. Koll, E.T. Lilleodden, M. Elbahri, The solvent induced interfiber adhesion and its influence on the mechanical and filtration properties of polyethersulfone electrospun nanofibrous microfiltration membranes, Sep. Purif. Technol. 98 (2012) 456–463. [16] A.-S. Jönsson, J. Lindau, R. Wimmerstedt, J. Brinck, B. Jönsson, Influence of the concentration of a low-molecular organic solute on the flux reduction of a polyethersulphone ultrafiltration membrane, J. Membr. Sci. 135 (1997) 117–128. [17] A. Cooper, R. Oldinski, H. Ma, J.D. Bryers, M. Zhang, Chitosan-based nanofibrous membranes for antibacterial filter applications, Carbohydr. Polym. 92 (2013) 254–259. [18] M. Aliabadi, M. Irani, J. Ismaeili, H. Piri, M.J. Parnian, Electrospun nanofiber membrane of PEO/Chitosan for the adsorption of nickel cadmium, lead and copper ions from aqueous solution, Chem. Eng. J. 220 (2013) 237–243. [19] M. Aliabadi, M. Irani, J. Ismaeili, S. Najafzadeh, Design and evaluation of chitosan/hydroxyapatite composite nanofiber membrane for the removal of heavy metal ions from aqueous solution, J. Taiwan Inst. Chem. Eng. 45 (2014) 518–526. [20] M. Kumar, B.P. Tripathi, V.K. Shahi, Crosslinked chitosan/polyvinyl alcohol blend beads for removal and recovery of Cd (II) from wastewater, J. Hazard. Mater. 172 (2009) 1041–1048. [21] J.H. Kim, J.Y. Kim, Y.M. Lee, K.Y. Kim, Properties and swelling characteristics of cross-linked poly (vinyl alcohol)/chitosan blend membrane, J. Appl. Polym. Sci. 45 (1992) 1711–1717. [22] B. Qi, A. Yu, S. Zhu, B. Chen, Y. Li, The preparation and cytocompatibility of injectable thermosensitive chitosan/poly (vinyl alcohol) hydrogel, J. Huazhong Univ. Sci. Technol. [Med. Sci.] 30 (2010) 89–93. [23] A. Esmaeili, A.A. Beni, A novel fixed-bed reactor design incorporating an electrospun PVA/chitosan nanofiber membrane, J. Hazard. Mater. 280 (2014) 788–796. [24] E. Erdem, N. Karapinar, R. Donat, The removal of heavy metal cations by natural zeolites, J. Colloid Interface Sci. 280 (2004) 309–314.

194

U. Habiba et al. / Journal of Hazardous Materials 322 (2017) 182–194

[25] D. Baybas¸, U. Ulusoy, Polyacrylamide–clinoptilolite/Y-zeolite composites: characterization and adsorptive features for terbium, J. Hazard. Mater. 187 (2011) 241–249. [26] I.K.D. Dimzon, T.P. Knepper, Degree of deacetylation of chitosan by infrared spectroscopy and partial least squares, Int. J. Biol. Macromol. 72 (2015) 939–945. [27] H. Homayoni, S.A.H. Ravandi, M. Valizadeh, Electrospinning of chitosan nanofibers: processing optimization, Carbohydr. Polym. 77 (2009) 656–661. [28] L. Li, Y.-L. Hsieh, Chitosan bicomponent nanofibers and nanoporous fibers, Carbohydr. Res. 341 (2006) 374–381. [29] Y.-T. Jia, J. Gong, X.-H. Gu, H.-Y. Kim, J. Dong, X.-Y. Shen, Fabrication and characterization of poly(vinyl alcohol)/chitosan blend nanofibers produced by electrospinning method, Carbohydr. Polym. 67 (2007) 403–409. [30] S. Mishra, S. Dubey, D. Tiwari, Ion-exchangers in radioactive waste management Part XIV: removal behavior of hydrous titanium oxide and sodium titanate for Cs(I), J. Radioanal. Nucl. Chem. 261 (2004) 457–463. ´ [31] J. Kumirska, M. Czerwicka, Z. Kaczynski, A. Bychowska, K. Brzozowski, J. Thöming, P. Stepnowski, Application of spectroscopic methods for structural analysis of chitin and chitosan, Mar. Drugs 8 (2010) 1567–1636. [32] M.R. Kasaai, A review of several reported procedures to determine the degree of N-acetylation for chitin and chitosan using infrared spectroscopy, Carbohydr. Polym. 71 (2008) 497–508. [33] N. Muhd Julkapli, H.M. Akil, Z. Ahmad, Preparation, properties and applications of chitosan-based biocomposites/blend materials: a review, Compos. Interfaces 18 (2011) 449–507. ´ ´ [34] R. Czechowska-Biskup, D. Jarosinska, B. Rokita, P. Ulanski, J.M. Rosiak, Determination of degree of deacetylation of chitosan-comparision of methods, Prog. Chem. Appl. Chitin Deriv. 17 (2012) 5–20. [35] Q. Li, E. Dunn, E. Grandmaison, M. Goosen, Applications and properties of chitosan, J. Bioact. Compat. Polym. 7 (1992) 370–397. [36] A.L. Yarin, Free liquid jets and films, Hydrodyn. Rheol. (1993). [37] H. Fong, D.H. Reneker, Elastomeric nanofibers of styrene-butadiene-styrene triblock copolymer, J. Polym. Sci. Part B Polym. Phys. 37 (1999) 3488–3493. [38] S.S. Homaeigohar, M. Elbahri, Novel compaction resistant and ductile nanocomposite nanofibrous microfiltration membranes, J. Colloid Interface Sci. 372 (2012) 6–15. [39] H. Fong, I. Chun, D. Reneker, Beaded nanofibers formed during electrospinning, Polymer 40 (1999) 4585–4592. [40] X. Song, F. Ling, L. Ma, C. Yang, X. Chen, Electrospun hydroxyapatite grafted poly(l-lactide)/poly (lactic-co-glycolic acid) nanofibers for guided bone regeneration membrane, Compos. Sci. Technol. 79 (2013) 8–14. [41] M.E. Frohbergh, A. Katsman, G.P. Botta, P. Lazarovici, C.L. Schauer, U.G. Wegst, P.I. Lelkes, Electrospun hydroxyapatite-containing chitosan nanofibers crosslinked with genipin for bone tissue engineering, Biomaterials 33 (2012) 9167–9178. [42] X. Chen, H. Yang, Z. Gu, Z. Shao, Preparation and characterization of HY zeolite-filled chitosan membranes for pervaporation separation, J. Appl. Polym. Sci. 79 (2001) 1144–1149. [43] M.-T. Yen, J.-H. Yang, J.-L. Mau, Physicochemical characterization of chitin and chitosan from crab shells, Carbohydr. Polym. 75 (2009) 15–21. [44] H. Zheng, Y. Du, J. Yu, R. Huang, L. Zhang, Preparation and characterization of chitosan/poly (vinyl alcohol) blend fibers, J. Appl. Polym. Sci. 80 (2001) 2558–2565. [45] H. Sun, L. Lu, X. Chen, Z. Jiang, Surface-modified zeolite-filled chitosan membranes for pervaporation dehydration of ethanol, Appl. Surf. Sci. 254 (2008) 5367–5374. [46] A. Kittur, S. Kulkarni, M. Aralaguppi, M. Kariduraganavar, Preparation and characterization of novel pervaporation membranes for the separation of water–isopropanol mixtures using chitosan and NaY zeolite, J. Membr. Sci. 247 (2005) 75–86. [47] K. Elaiopoulos, T. Perraki, E. Grigoropoulou, Monitoring the effect of hydrothermal treatments on the structure of a natural zeolite through a combined XRD, FTIR XRF, SEM and N 2-porosimetry analysis, Microporous Mesoporous Mat. 134 (2010) 29–43. [48] J. Bai, Y. Li, S. Yang, J. Du, S. Wang, J. Zheng, Y. Wang, Q. Yang, X. Chen, X. Jing, A simple and effective route for the preparation of poly(vinylalcohol)(PVA) nanofibers containing gold nanoparticles by electrospinning method, Solid State Commun. 141 (2007) 292–295. [49] A. C¸ay, M. Miraftab, E.P.A. Kumbasar, Characterization and swelling performance of physically stabilized electrospun poly (vinyl alcohol)/chitosan nanofibres, Eur. Polym. J. 61 (2014) 253–262. [50] Y. Zhu, C.E. Bakis, J.H. Adair, Effects of carbon nanofiller functionalization and distribution on interlaminar fracture toughness of multi-scale reinforced polymer composites, Carbon 50 (2012) 1316–1331. [51] M.N.R. Kumar, A review of chitin and chitosan applications, React. Funct. Polym. 46 (2000) 1–27.

[52] L. Jeong, W.H. Park, Preparation and characterization of gelatin nanofibers containing silver nanoparticles, Int. J. Mol. Sci. 15 (2014) 6857–6879. [53] H. Zhu, R. Jiang, L. Xiao, L. Liu, C. Cao, G. Zeng, CdS nanocrystals/TiO 2/crosslinked chitosan composite: facile preparation, characterization and adsorption-photocatalytic properties, Appl. Surf. Sci. 273 (2013) 661–669. [54] W. Plazinski, W. Rudzinski, A. Plazinska, Theoretical models of sorption kinetics including a surface reaction mechanism: a review, Adv. Colloid Interface Sci. 152 (2009) 2–13. [55] Y.-S. Ho, G. McKay, Pseudo-second order model for sorption processes, Process Biochem. 34 (1999) 451–465. [56] Y.-S. Ho, Review of second-order models for adsorption systems, J. Hazard. Mater. 136 (2006) 681–689. [57] N. Arancibia-Miranda, J. Silva-Yumi, M. Escudey, Effect of cations in the background electrolyte on the adsorption kinetics of copper and cadmium and the isoelectric point of imogolite, J. Hazard. Mater. 299 (2015) 675–684. [58] L. Cáceres-Jensen, J. Rodríguez-Becerra, J. Parra-Rivero, M. Escudey, L. Barrientos, V. Castro-Castillo, Sorption kinetics of diuron on volcanic ash derived soils, J. Hazard. Mater. 261 (2013) 602–613. [59] L. Xiong, Y. Yang, J. Mai, W. Sun, C. Zhang, D. Wei, Q. Chen, J. Ni, Adsorption behavior of methylene blue onto titanate nanotubes, Chem. Eng. J. 156 (2010) 313–320. [60] M. Kumar, R. Tamilarasan, V. Sivakumar, Adsorption of Victoria blue by carbon/Ba/alginate beads: kinetics, thermodynamics and isotherm studies, Carbohydr. Polym. 98 (2013) 505–513. [61] H. Zhang, X. Gao, T. Guo, Q. Li, H. Liu, X. Ye, M. Guo, Z. Wu, Adsorption of iodide ions on a calcium alginate-silver chloride composite adsorbent, Colloids Surf. A: Physicochem. Eng. Aspects 386 (2011) 166–171. [62] G. Jing, Z. Zhou, L. Song, M. Dong, Ultrasound enhanced adsorption and desorption of chromium (VI) on activated carbon and polymeric resin, Desalination 279 (2011) 423–427. [63] R.t. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Crystallogr. Sect. A 32 (1976) 751–767. [64] E. Guibal, Interactions of metal ions with chitosan-based sorbents: a review, Sep. Purif. Technol. 38 (2004) 43–74. [65] F.T.R. de Almeida, B.C.S. Ferreira, A.L.d.S.L. Moreira, R.P. de Freitas, L.F. Gil, L.V.A. Gurgel, Application of a new bifunctionalized chitosan derivative with zwitterionic characteristics for the adsorption of Cu 2+, Co 2+, Ni 2+, and oxyanions of Cr 6+ from aqueous solutions: kinetic and equilibrium aspects, J. Colloid Interface Sci. 466 (2016) 297–309. [66] H. Beheshti, M. Irani, L. Hosseini, A. Rahimi, M. Aliabadi, Removal of Cr (VI) from aqueous solutions using chitosan/MWCNT/Fe 3 O 4 composite nanofibers-batch and column studies, Chem. Eng. J. 284 (2016) 557–564. [67] H.H. Najafabadi, M. Irani, L.R. Rad, A.H. Haratameh, I. Haririan, Removal of Cu2+, Pb2+ and Cr6+ from aqueous solutions using a chitosan/graphene oxide composite nanofibrous adsorbent, RSC Adv. 5 (2015) 16532–16539. [68] A.C. Zimmermann, A. Mecabô, T. Fagundes, C.A. Rodrigues, Adsorption of Cr(VI) using fe-crosslinked chitosan complex (Ch-Fe), J. Hazard. Mater. 179 (2010) 192–196. [69] Y.G. Abou El-Reash, M. Otto, I.M. Kenawy, A.M. Ouf, Adsorption of Cr(VI) and As(V) ions by modified magnetic chitosan chelating resin, Int. J. Biol. Macromol. 49 (2011) 513–522. [70] M. Al-Anber, Z.A. Al-Anber, Utilization of natural zeolite as ion-exchange and sorbent material in the removal of iron, Desalination 225 (2008) 70–81. [71] Z. Zang, Z. Hu, Z. Li, Q. He, X. Chang, Synthesis, characterization and application of ethylenediamine-modified multiwalled carbon nanotubes for selective solid-phase extraction and preconcentration of metal ions, J. Hazard. Mater. 172 (2009) 958–963. [72] K.N. Ghimire, J.i. Inoue, K. Inoue, H. Kawakita, K. Ohto, Adsorptive separation of metal ions onto phosphorylated orange waste, Sep. Sci. Technol. 43 (2008) 362–375. [73] S¸. Tokalıo˘glu, V. Yılmaz, S¸. Kartal, A. Delibas¸, C. Soykan, Synthesis of a novel chelating resin and its use for selective separation and preconcentration of some trace metals in water samples, J. Hazard. Mater. 169 (2009) 593–598. [74] S.B. Khan, M.M. Rahman, H.M. Marwani, A.M. Asiri, K.A. Alamry, M.A. Rub, Selective adsorption and determination of iron (III): Mn 3 O 4/TiO 2 composite nanosheets as marker of iron for environmental applications, Appl. Surf. Sci. 282 (2013) 46–51. [75] Y. Vijaya, S.R. Popuri, V.M. Boddu, A. Krishnaiah, Modified chitosan and calcium alginate biopolymer sorbents for removal of nickel (II) through adsorption, Carbohydr. Polym. 72 (2008) 261–271. [76] M.V. Dinu, E.S. Dragan, Evaluation of Cu 2+, Co 2+ and Ni 2+ ions removal from aqueous solution using a novel chitosan/clinoptilolite composite: kinetics and isotherms, Chem. Eng. J. 160 (2010) 157–163.