activated carbon composite film for Cd2+ removal

Accepted Manuscript Title: Preparation of Polyethylene Glycol Diglycidyl Ether (PEDGE) Crosslinked Chitosan/Activated Carbon Composite Film for Cd2+ Removal Authors: Rahmi, Lelifajri, Rizki Nurfatimah PII: DOI: Reference:

S0144-8617(18)30842-7 https://doi.org/10.1016/j.carbpol.2018.07.051 CARP 13851

To appear in: Received date: Revised date: Accepted date:

27-3-2018 9-7-2018 16-7-2018

Please cite this article as: Rahmi, Lelifajri, Nurfatimah R, Preparation of Polyethylene Glycol Diglycidyl Ether (PEDGE) Crosslinked Chitosan/Activated Carbon Composite Film for Cd2+ Removal, Carbohydrate Polymers (2018), https://doi.org/10.1016/j.carbpol.2018.07.051 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Preparation of Polyethylene Glycol Diglycidyl Ether (PEDGE) Chitosan/Activated Carbon Composite Film for Cd2+ Removal

Crosslinked

Rahmi*, Lelifajri, Rizki Nurfatimah Department of Chemistry, Syiah Kuala University, Banda Aceh, 23111, Indonesia *[email protected]

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Highlights

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 Activated carbon and PEDGE improve mechanical properties of chitosan film  Activated carbon is produced by pyrolysis process of oil palm empty fruit bunch.  Adsorption capacity of the composite film is higher than chitosan film  The composite film is low cost adsorbent with high performance.

Abstract

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Preparation and characterization of polyethylene glycol diglycidyl ether (PEDGE) crosslinked chitosan/activated carbon composite film have been conducted. PEDGE was used as crosslinking agent and activated carbon as a filler on composite film preparation. The composite films were produced with several ratios of chitosan/PEDGE/activated carbon. Tensile test, Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD) and Scanning Electon Microscope (SEM) were used to study the structure and properties of PEDGE crosslinked chitosan/activated carbon composite film. Tensile test results showed crosslinking and filler influenced the tensile strength of composite films. The best composite film was obtained at 0.70/0.10/0.20 mixing ratio of chitosan/PEDGE/activated carbon. FTIR, SEM and XRD analysis confirmed the formation of PEDGE crosslinked chitosan/activated carbon composite films. The obtained PEDGE crosslinked chitosan/activated carbon composite film was used for adsorption of Cd2+. The highest adsorption capacity of Cd2+ was obtained at pH 5 and 40 minutes contact time. Based on Langmuir adsorption isotherm model, the maximum adsorption capacity (Q) of Cd2+ by PEDGE crosslinked chitosan/activated carbon composite film was 357.14 mg/g. Regeneration studies showed the PEDGE crosslinked chitosan/activated carbon composite film can be used repeatly with high performance.

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Keywords: Chitosan, PEDGE, activated carbon, crosslinking, filler, adsorption 1. Introduction The increasing of heavy metal ions contamination in the environment has become the most urgent environmental problem (Jia, Wang, Wu, & Li, 2014). One of heavy metals that has a contribution of toxicity in the water is cadmium (Bunce,1994). Cadmium causes muscular cramps, chronic pulmonary problems, proteinuria, skeletal deformity, testicular atrophy, high blood pressure, kidney damage, renal disorder and human carcinogen (Sharififard, Nabavinia, & Soleimani, 2016; Barakat, 2011). Therefore, it is important to 1

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remove cadmium from wastewater of industries. At present, it has been used various methods to remove cadmium from wastewater, including adsorption. In recent years, researchers have used a variety of adsorbents for adsorption of cadmium from aqueous solution. Adsorbents were obtained from biomass or biopolymers, such as corn stalk powder (El-Sayed, Dessuoki, & Ibrahiem, 2011), and chitosan (Bamgbose, Adewuyi, Bamgbose, & Adetoye, 2010). Chitosan is an adsorbent which has a high adsorption capacity due to the amino and hydroxyl groups contained in chitosan can serve as coordination sites to bind heavy metals (Dalida, et al., 2011). It is also known as low cost, non-toxic, biodegradable, renewable and efficient adsorbent. However, the use of pure chitosan as an adsorbent has some drawbacks, such as low chemical stability and weak mechanical properties (Tran, Duri, Delneri, & Franko, 2013). These drawbacks can be overcome by several methods such as addition of crosslinking agent or filler on adsorbent preparation. Crosslinking can improve chitosan resistance to acids, stability of chitosan, and adsorption capacity. Wan Ngah (2002) stated that the crosslinked chitosan has better resistance to acids than pure chitosan. The addition of filler reinforces the mechanical strenght of composite. The reinforcing effect is determined by particle size, grain fineness, the flatness of the deployment and the state of the surface of filler. Filler is an additive that has a solid phase included in the polymer matrix (Harper, 2002). Activated carbon is the most common filler due to its physical and chemical properties which considered to have the greatest influence on the mechanical properties of the polymers in a variety of ways and levels (Patel & Brown, 1985). Karaer & Kaya (2016) reported the use of activated carbon on chitosan beads preparation. Sharififard, Nabavinia, & Soleimani (2016) reported the preparation of activated carbon coated with chitosan. However, most of activated carbon used was commercial activated carbon resulting high-cost materials. Peruelo et al. (2017) reported the use of bamboo activated carbon for chitosan composite preparation. There is no report the use of activated carbon prepared from oil palm empty fruit bunch as a filler on chitosan composite film preparation.Whereas, it is known that oil palm empty fruit bunch has high potencial as activated carbon resource. It contains 37.3 - 46.5% of cellulose and 25.3- 33.8% of hemicelluloses (Sudiyani et al., 2013). In this study activated carbon was derived from oil palm empty fruit bunch. It was solid waste from the palm oil industry. Activated carbon obtained from oil palm empty fruit bunch has a lower cost compared to commercial activated carbon. The use of activated carbon from the oil palm empty fruit bunch will provide added value for the palm oil industry waste. The preparation of PEDGE crosslinked chitosan/activated carbon composite film was conducted with various content of chitosan, activated carbonfrom oil palm empty fruit bunch and crosslinking agent polyethylene glycol diglycidyl ether (PEDGE). The adsorbent obtained was characterized by tensile test, FTIR, SEM and XRD. The adsorption experiments were performed with various contact time, pH and initial concentration of Cd2+. 2. Materials and Methods

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2.1 Materials Chitosan, derived from deacetylated shrimp shell, was purchased from Tokyo Chemical Industry Co., Ltd. Japan (degree of deacetylation: 75.0-85.0%; the viscosity: 200500mPas, 0.5% in 0.5% Acetic acid at 20°C). All other chemicals were analytical grade. Oil palm empty fruit bunch was obtained from Aceh, Indonesia. 2.2 Preparation of oil palm empty fruit bunch activated carbon Oil palm empty fruit bunch was washed several times using distilled water and then dried. The dried oil palm empty fruit bunch was pyrolyzed in the furnace at 500°C for 2 hours.

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The obtained activated carbon was sieved (< 100 mesh) and then grounded into powder using a ball mill at 300 rpm for 5 hours.

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2.3 Preparation of PEDGE crosslinked chitosan/activated carbon composite films Chitosan solution was prepared by mixing chitosan powder in 100 mL of acetic acid (2%). PEDGE was then added and stirred approximately 4 h using a magnetic stirrer at room temperature. Activated carbon was dispersed in distilled water and then added into the chitosan solution and stirred for 2 h. Dope solution was poured onto PET plastic container and dried for 20 h at 40°C and then the resulted film was released from plastic container. The content of chitosan, PEDGE and activated carbon were varied as show in Table 1, where the total mass of components was 1 gram.

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2.4 Tensile test Tesile test was performed with the Universal Testing Machine (UTM) Huang Ta. The specimens of PEDGE crosslinked chitosan/activated carbon composite film were prepared based on ASTM D638. The strain rate was 20 mm/s.

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2.5 FTIR FTIR spectra were obtained by Cary 630 Fourier Transform Infrared Spectrometer (Agilent Technologies). Spectral scanning was acquired in a wavenumber ranged from 4000 to 600 cm-1.

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2.6 XRD XRD patterns were obtained with the Shimadzu XRD-700 Series X-Ray Diffractometer operating at 40kV and 30mA producing CuK with λ= 0.154 nm in the range of 2 = 10-70 using a step size of 0.02/min.

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2.7 SEM Samples were coated with a 200 Å - thick gold layer. Micrographs were obtained with JSM-6510A/JSM-6510LA (Analytical/Analytical low vacuum SEM). SEM images were obtained at 5000x magnification.

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2.8 Adsorption studies Adsorption studies were performed with a series of adsorption experiments at room temperature. The Cd2+ solutions with different concentrations were prepared by dissolving Cd(NO3)2 in deionized water. The adsorbent dose was 0.05 g in 25 mL of Cd2+ solution. The composite film was cut into small pieces (1×1 cm) and weighed (0.05 g). Small pieces of PEDGE crosslinked chitosan/activated carbon composite film were placed in an erlenmeyer flask containing 25 mL of Cd2+solution with initial concentration and pH were 10 ppm and 5, respectively. The mixture was shaken with a constant speed of 150 rpm for 40 min and then filtered. The final Cd2+concentration was determined by using UV–Vis spectrophotometer (UVmini-1240, Shimadzu). The spectrophotometry analysis was conducted with dithizone method at wavelength of 229 nm, sensitivity of 0.001 with interval concentration of blank analysis was 5–10 ppm. In order to study the effect of contact time and pH, the same procedure was conducted with the different contact time (20, 25,30, 35, 40 and 50 min) and pH (2, 3, 4, 5, 6, 7, 8, and 9). The pH values were adjusted by using HCl 1M and NaOH 1M. To study adsorption isotherms, the adsorption experiments were carried out with several Cd2+ initial concentrations (25, 35, 45, 55, 65 and 200 ppm) at initial pH 5 for 40 min.

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2.9. Regeneration studies Film regenerations were conducted by using HNO3 0.001 N. The used adsorbent (film) was soaked into HNO3 solution. Then the adsorbent was separated from the solution and washed until neutral pH was reached. The adsorbent was then dried and reused as an adsorbent. The regeneration was conducted four times for both composite film and chitosan film. 3. Result and discussion

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3.1 Characterization PEDGE crosslinked chitosan/activated carbon composite film was prepared with a variety of chitosan, PEDGE and activated carbon contens as shown in Table 1. The pictures of chitosan film and PEDGE crosslinked chitosan/activated carbon composite film were shown in Figure 1. Figure 1a showed the yellowish transparent film of pure chitosan and Figure 1b showed the PEDGE crosslinked chitosan/activated carbon composite film with black color due to the addition of activated carbon.

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Different composition affected the film behaviour, where only the appropriate composition resulted: (a) good adhesion between matrix-filler that improved tensile strength of the film and (b) high adsorption capacity. In order to obtained the appropriate composition, the films were prepared in several compositions of chitosan (matrix), PEDGE (crosslinking agent) and activated carbon (filler). If the filler content is too high, the cohesion will be dominant than adhesion force and reduce the tensile strength of the film. If crosslinking is too much, the active sites of chitosan will be binded with crosslinking agent leading chitosan to lose of its active sites and the adsorption capacity to be decreased. The best film as an adsorbent is the film that has high both adsorption capacity and tensile strength. In order to select the best composite film, SAW method was used with two criteria (tensile strength and adsorption capacity). The priority percentage of tensile strength and adsorption capacity was 40 and 60%, respectively. Each obtained PEDGE crosslinked chitosan/activated carbon composite films were analyzed by tensile test and examined their adsorption capacity. The results were shown in Table 1. The last column of Table 1 showed the normalized priority index (Npi) obtained for both criteria. Npi equal to 1 means that the corresponding alternative is the best alternative (marked with an asterisk). Therefore, the composite film containing chitosan 0.7, PEDGE 0.1, and activated carbon 0.2 % was chosen as the best composite film and used as an adsorbent of Cd2+ ions. The adsorption capacity was influenced by the content of PEDGE, chitosan and activated carbon. Tensile strength of pure chitosan film was 12.30 kgf/mm2. The value was lower than tensile strength of PEDGE crosslinked chitosan/activated carbon composite film. It indicated addition of activated carbon and crosslinking agent improved mechanical properties of chitosan film. In order to study the structure of materials, FTIR spectroscopy was performed and the results were shown in Figure 2. Figure 2a showed typical spectrum of chitosan where the band at 3422 cm-1 confirmed the NH2 stretching vibration of chitosan. Band of OH stretching vibration appeared at 3230 cm-1. Bending vibration of CH aliphatic, CH2 and amide II were confirmed by the bands at 2970, 2922 and 1575 cm-1, respectively. Figure 2b showed FTIR spectrum of activated carbon prepared from oil palm empty fruit bunch. Activated carbon does not contain carbon atoms alone, but some heteroatoms like 4

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oxygen, hydrogen, nitrogen, etc are bonded to the edges of the carbon layers. Bands at 2374, 1560, 874 and 1034 cm-1 confirmed acetylene vibration, C=C aromatic, alkene vibration and streching vibration of ether, respectively. The similar result was also reported by Wibowo et al. (2011) for activated carbon prepared from nyamplung shell beans, where activated carbon showed the absorption bands of C-H, C-O, and C = C. FTIR spectrum of PEDGE crosslinked chitosan (2c) was different with FTIR spectrum of chitosan. Band at wave number of 3422 cm-1 was not apperared in FTIR spectrum of PEDGE crosslinked chitosan. It was due to the increase of OH groups, as a consequence of the addition of PEDGE as crosslinking agent. Where crosslinking occured between NH2 functional groups of chitosan and epoxide functional groups of PEDGE, the new OH groups were formed. Band of OH stretching vibration covered the appearance of NH2 stretching vibration band of chitosan. In addition, intensity of ether vibration band of chitosan increased on PEDGE crosslinked chitosan film spectrum at wave number 1018 cm-1 due to ether contribution of PEDGE. The results confirmed the formation of crosslinking of chitosan by PEDGE. FTIR spectrum of PEDGE crosslinked chitosan/activated carbon composite film (Figure 2d) showed a combination of PEDGE crosslinked chitosan and activated carbon spectra. Bands contained on the chitosan and activated carbon spectra also appeared on FTIR spectrum of PEDGE crosslinked chitosan composite film. However, OH stretching band of chitosan shifted to lower wave number on PEDGE crosslinked chitosan/activated carbon composite film and CH3 bending band of activated carbon shifted to higher wave number (1406 cm-1) on PEDGE crosslinked chitosan/activated carbon composite film .

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Compared with activated carbon spectrum, ether vibration band shifted to lower wave number (1017 cm-1) on PEDGE crosslinked chitosan/activated carbon composite film spectrum. The band at 874 cm-1 shifted to 897 cm-1on PEDGE crosslinked chitosan/activated carbon composite film spectrum. These shifts confirmed interactions between activated carbon and chitosan that lead good adhesion between matrix and filler.

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XRD analysis was performed on chitosan film, activated carbon and PEDGE crosslinked chitosan/activated carbon composite film and the results were shown in Figure 3. Chitosan showed a higher crystallinity than activated carbon and PEDGE crosslinked chitosan/activated carbon composite film. Zhang et al., 2003 reported chitosan diffractogram showed 2θ at 5-30o. In this study, chitosan diffractogram showed 2θ at 20.04° (Figure 3a). This resultwas similar with theresearch reported by Ali et al., (2011) for chitosanused as the polyester bioactivation. . XRD diffractograms of activated carbon (Figure 3b) showed an amorphous phase. Diffractogram of activated carbon exhibited 2θ at 29.55°;26.58° and 23.63° with crystallinity was only 25.25%. These results are consistent with the results reported by Destyorini et al.,(2010) for activated carbon of coconut fibers prepared with activation temperature at 500°C,where the 2θ was at 28.55o with crystallinity 26.25%. The PEDGE crosslinked chitosan/activated carbon composite film diffractogram showed a decrease in the intensity and peak broadening. This indicated the change of chitosan phase becomed more amorphous. Distribution filler in PEDGE crosslinked chitosan composite film was confirmed by SEM analyisis. Figure 4a showed the surface of pure chitosan film at 5000x magnification. The surface was smooth compared with the composite PEDGE crosslinked chitosan composite film (Figure 4c). Figure 4b showed particles of activated carbon at 5000x magnification. Based on Figure 4b, the average particle size of activated carbon was 0.7 µm.

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Figure 4c showed the PEDGE crosslinked chitosan composite film. SEM images of PEDGE crosslinked chitosan composite film showed the distribution of the activated carbon in the chitosan film and confirmed the formation of filler in the composite.

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3.2 Adsorption studies Adsorption studies were conducted with various contact time, pH and concentration. The results of Cd2+ adsorption by PEDGE crosslinked chitosan composite film with contact time variation was shown in Figure 5. At initial time of adsorption, Figure 5 showed an increase in the adsorption of Cd2+ with increasing contact time until contact time of 40 minutes. However, adsorption decreased at contact time 45 minutes. The increasing was due to the large amount of empty active sites in composite. By increasing contact time, the amount of empty active sites decreased and the adsorption of Cd2+ reached equilibrium at 40 minutes with adsorption capacity of 2.440 mg/g and persentage of removal was 48.8%. In order to study effect of pH on adsorption of Cd2+ by PEDGE crosslinked chitosan/activated carbon composite film, the experiments were performed with various initial pH (2, 3, 4, 5, 6, 7, 8 and 9). Experiments were conducted with contact time 40 minutes and Cd2+ initial concentration was 10 ppm cadmium. pH was adjustment using NaOH 0.1 N solution and HCl 0.1 N. The experiment was not performed at pH below 2 in order to avoid dissolution of composites and above 9 in order to avoid precipitation of Cd2+. The results were shown in Figure 6. Based on Figure 6, the highest adsorption capacity of cadmium metal ions was obtained at pH 5. The adsorption capacity was decrease at higher and lower pH. In acidic solution, the free amino groups (NH2) on chitosan will be protonated to be NH3+ (Madala etal.,2013). At low pH, the protons will be occupied with the most surface of adsorbent and lead to the low adsorption of cadmium metal ion due to the electrostatic repulsion. By increasing pH, the adsorption capacity increased due to the presence of protons in solutions decrease and the competition between H+ and cadmium metal ions binding with amino groups also decrease. However, the precipitation of cadmium can cause a decrease in the adsorption capacity above pH 8. The results showed that the optimum pH of cadmium metal ion adsorption was pH 5 with adsorption capacity 3.160 mg/g and removal 63.2%.

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In this work, the adsorption isotherms were studied based on Langmuir and Freundlich models. The experiments were conducted with several initial concentrations of Cd2+ (15, 25, 35, 45, 55, 65 and 200 ppm) at initial pH 5 for 40 minutes. The Langmuir and Freundlich equations were shown in equation 1 and 2, respectively. qe is the amount of adsorbed Cd2+ (mg/g) for monolayer coverage. Ce is the equilibrium concentration of Cd2+ (mg/L), Qmax is maximum amount of Cd2+ per unit weight of adsorbent (mg/g) for monolayer coverage and KL is the Langmuir adsorption equilibrium constant (L/mg). Kf is adsorption capacity of the adsorbent (mg/g) and n is Freundlich constant that indicates favorability of adsorption. Adsorption isotherms of PEDGE crosslinked chitosan composite film for Cd2+ was shown in Figure 7.

𝑞𝑒 =

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𝑞𝑒 = 𝐾𝑓 𝐶𝑒𝑛

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The qmax of adsorption Cd2+ on PEDGE crosslinked chitosan/activated carbon composite film was 357.14 mg/g. This value is higher than Qmax of some other adsorbents as shown in Table 2. It indicates that PEDGE crosslinked chitosan/activated carbon composite film has high potential to be used as an adsorbent of Cd2+.

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Comparison of Langmuir and Freundlich model of Cd2+ adsorption on PEDGE crosslinked chitosan/activated carbon composite film was shown in Table 3. R2 values obtained of both models were higher than 0.9. It indicated that the adsorption of Cd2+ on PEDGE crosslinked chitosan/activated carbon composite film fitted to both models. The similar result was also found by Dehghani et al. (2017) for adsorption of bromophenol red on MFe2O4 Ferrite Spinel, where the adsorption fitted to both Langmuir and Freundlich isotherm models.

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Langmuir isotherm model assumes the homogeneous adsorption and Freundlich isotherm model assumes heterogeneous adsorption. The strength of the interaction between the adsorbent and adsorbate can be expressed using n value. If n<1, the adsorption process is physical adsorption. If n>1, the adsorption is chemical adsorption (Chou et al., 2010). In this work, the value of n was 0.982 that indicates the adsorption processes is physical adsorption.

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3.3 Regeneration studies In order to study the possibility of adsorbent to be used for several times, regeneration of adsorbent was conducted in this work. Adsorbent regeneration is the process of reproducing the adsorbent that has been used in the adsorption process. This regeneration process is one of the important factors in the industry, where wastewater treatment becomes more economical. The regeneration was began with the desorption process of cadmium metal ions retained on the adsorbent. Desorption was done by soaking the adsorbent into a solution of HNO3 0.001 N. Then the adsorbent was separated from the solution and washed until neutral pH. The adsorbent was then dried and reused as an adsorbent. The results obtained were shown in Figure 8. Figure 8 showed adsorption capacity of PEDGE crosslinked chitosan/activated carbon composite film was higher than chitosan film. The adsorption capacity of chitosan film decreased significantly after third regeneration, and unable to adsorp Cd2+ after fourth regeneration. Adsorption capacity of PEDGE crosslinked chitosan/activated carbon composite film after regeneration was also decreased. It was due to regeneration process decreases the content of nitrogen in the adsorbent as shown in Table 4, where nitrogen is known as one of active sites of the adsorbent. Swelling ratio of chitosan film and PEDGE crosslinked chitosan/activated carbon composite film were 474.42 and 46.09%, respectively. The swelling ratio of chitosan was ten times higher than swelling ratio of the composite. It was due to the composite film contained filler (activated carbon) in appropriorate composition where the adhesion force matrix-filler was favorable. In addition crosslinking in the composite film reduced the mobility of polymer chain of chitosan that caused the decrease of swelling ratio. Low swelling ratio of film prevented the dissolution of the film in the solution and the desorption of adsorbed adsorbate. It improved adsorption capacity and the film can be used for several times. Compared with adsorption capacity of chitosan film, the adsorption capacity of the PEDGE crosslinked chitosan/activated carbon composite film showed higher adsorption

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capacity. The high adsorption capacity of PEDGE crosslinked chitosan/activated carbon composite film was contributed by the filler and PEDGE which contained several fuctional groups. In addition, filler and crosslinking provided a good mechanical properties of adsorbent because of that the adsorbent still showed good performance after used several times.

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4. Conclusions Activated carbon from oil palm empty fruit bunch has been produced and used as filler on PEDGE crosslinked chitosan/activated carbon composite film preparation. PEDGE crosslinked chitosan/activated carbon composite films were produced with various contents of chitosan, PEDGE and activated carbon. The composite films were analized using FTIR,XRD,SEM and tensile test. Results showed activated carbon loading was a good reinforcement of chitosan film. It improved the tensile strength of chitosan film due to a good adhesion of the matrix-filler interface. PEDGE crosslinked chitosan/activated carbon composite film was applied as an adsorbent of Cd2+. Results showed the highest adsorption capacity was found at pH 5 with a contact time of 40 minutes. Langmuir and Freundlich adsorption isotherm models were used to study the adsorption equilibrium. The maximum adsorption capacity (Qmax) was 357.14 mg/g. Based on regeneration studies, PEDGE crosslinked chitosan/activated carbon composite film showed higher performance than pure chitosan. It suggests PEDGE crosslinked chitosan/activated carbon composite film is a high potential adsorbent for adsorption of Cd2+.

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Acknowledgment The author gratefully acknowledge the financial support from Indonesian Directorate General of Higher Education (DIKTI)

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Figure 1. Images of chitosan film (a) and PEDGE crosslinked chitosan/activated carbon composite film (b).

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Figure2. FTIR spectra of pure chitosan film (a), activated carbon (b), PEDGE crosslinked chitosan (c), and PEDGE crosslinked chitosan/activated carbon composite film (d)

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Figure 3. XRD diffractograms of chitosan film (a) activated carbon (b) PEDGE crosslinked chitosan/activated carbon composite film

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Figure 4. SEM results of chitosan film (a) activated carbon (b) and PEDGE crosslinked chitosan/activated carbon composite film (c)

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30 35 t (min)

40

SC R

0.0 45

A

CC

EP

TE D

M

A

N

U

Figure 5. Influence of contact time onadsorption capacity (Q) of Cd2+ from water by PEDGE crosslinked chitosan composite film

15

3.5 3.0

2.0 1.5

IP T

Q (mg/g)

2.5

1.0

SC R

0.5 0.0 2

3

4

5

6

7

8

9

A

CC

EP

TE D

M

A

N

U

pH Figure 6. Influence of pH on adsorption capacity (Q) of Cd2+ from water by PEDGE crosslinked chitosan composite film

16

70 Experiment

60

Langmuir Freundlich

40 30

IP T

qe (mg/g)

50

20

SC R

10 0 0

20

40 60 Ce (mg/L)

80

100

A

CC

EP

TE D

M

A

N

U

Figure 7. Adsorption isotherms of PEDGE crosslinked chitosan composite film for Cd2+

17

3.5 Chitosan film 3.0

PEDGE crosslinked chitosan/activated carbon composite film

Q (mg/g)

2.5 2.0

IP T

1.5

0.5 WR

R1

R2

R3

R4

SC R

1.0

A

CC

EP

TE D

M

A

N

U

Figure 8. Comparison of adsorption capacity of Cd2+ on chitosan film and PEDGE crosslinked chitosan/activated composite film after regeneration. (WR: without regeneration, R1:first regeneration, R2: second regenerating, R3: third regeneration and R4: fourth regeneration).

18

tensile strength and

Q (mg / g)

U

N

A

M

TE D

EP CC A

19

Npi 0.67 0.80 0.53 0.58 0.59 0.71 0.30 0.80 0.68 0.73 0.86 0.86 0.52 0.79 0.76 0.66 1.00 0.77 0.60 0.67 0.91 0.95 0.98 0.63 0.71

IP T

1.320 1.780 1.210 0.765 1.340 1.645 0.370 1.585 1,385 1.285 1.755 1.975 1.140 1.625 1.515 1.225 2.415 1.580 1.095 1.185 2.235 2.175 2.350 0.985 1.230

SC R

Table 1. Values obtained based on SAW method with two criteria, adsorption capacity of Cd2+ (Q) PEDGE crosslinked chitosan Criteria (C) composite film Tensile strength (kgf /mm2) (chitosan: PEDGE: activated carbon) 0.90 : 0.05: 0.05 17.00 0.85: 0.10: 0.05 17.60 0.80: 0.15: 0.05 11.20 0.75: 0.15: 0.05 19.50 0.70: 0.25: 0.05 12.40 0.85: 0.05: 0.10 14.70 0.80: 0.10:0.10 10.40 0.75: 0.15: 0.10 20.20 0.70: 0.20: 0.10 16.50 0.65: 0.25: 0.10 20.20 0.80: 0.05: 0.15 20.80 0.75: 0.10: 0.15 17.80 0.70: 0.15: 0.15 11.80 0.65: 0.20: 0.15 19.20 0.60: 0.25: 0.15 19.10 0.75: 0.05: 0.20 17.70 0.70: 0.10: 0.20* 19.40 0.65: 0.15: 0.20 18.30 0.60: 0 20: 0.20 16.30 0.55: 0.25: 0.20 18.50 0.70: 0.05: 0.25 17.30 0.65: 0.10: 0.25 19.80 0.60: 0.15: 0.25 19.20 0.55: 0.20: 0.25 19.20 0.50: 0.25: 0.25 20.10

A

CC

EP

TE D

M

A

N

U

SC R

IP T

Table 2. Comparison of the maximum adsorption capacity of Cd2+ by some adsorbents Adsorbent Qmax (mg/g) Reference Rice husk 21.28 Kumar et al., 2010 Algerian cork 9.65 Krika et al., 2016 NaOH-Activated Carbon 100 Gaya et al., 2015 Sugarcanne Bagasse 6.79 Ibrahim et al., 2006 Chitosan Composite Biosorbent 95.2-108.7 Madala et al., 2013 PEDGE crosslinked 357.14 This work chitosan/activated carbon composite film

20

A

CC

EP

TE D

M

A

N

U

SC R

IP T

Table 3. Comparison of Langmuir and Freundlich models of Cd2+ adsorption on PEDGE crosslinked chitosan/activated carbon composite film Langmuir model Freundlich model 2 Qmax (mg/g) KL R Kf n R2 357.14 0.002 0.998 0.678 0.982 0.997

21

A

CC

EP

TE D

M

A

N

U

SC R

IP T

Table 4. Elements content of PEDGE crosslinked chitosan/activated carbon composite film before and after regeneration Element Weight % Composite film before regeneration Composite film after regeneration Carbon 38.774 52.412 Nitrogen 14.575 8.199 Oxygen 46.651 39.389

22