Crosslinked Chitosan Resin Research Articles

Removal of cadmium from aqueous solution using modified magnetic glycine modified cross-linked chitosan resin

In the present study, the adsorption of Cd(II) ions onto magnetic glycine modified crosslinked chitosan (MGMCR) resin has been investigated. Batch experiments were performed to study the effect of some parameters such as the initial Cd(II) concentration, pH value of the solution, adsorbent dose and the contact time on the adsorption process. The optimal pH for the adsorption of Cd(II) was found to be at 5 and the equilibrium was accomplished within 120 minutes. The result obtained from equilibrium adsorption studies are fitted in Langmuir and Freundlich adsorption models and the data was found to agree well with the Langmuir model. The maximum uptake was found to be 172 mg g-1 at 25 0C at pH 5.

Effect of aliphatic diamine spacer length on enzymatic performance of myrosinase immobilized on chitosan microsphere and its application for sulforaphene production

Glucosinolates can be hydrolyzed by the enzyme commonly known as myrosinase (E.C. 3.2.1.147) to a variety of biological compounds. Myrosinase (MYR) has been immobilized through the flexible spacers of different length on cross-linked chitosan resin (CCR). Ethylene diamine, hexamethylenediamine and decamethylene-diamine have been separately used as spacers. The influence of the flexible spacer length on the immobilized MYR (IMYR) properties were evaluated. The optimum pH and Vmax of IMYR linearly increase with the flexible spacer length, and the optimum temperature and Km of IMYR show an opposite trend. The recyclability of IMYR was good, with 90% recovery of activity after 10 cycles and 80% recovery after 30 cycles. IMYR was highly stable under storage conditions, with 95% recovery of activity after one year storage at 4 °C. The IMYR with the longest flexible spacer, decamethylene-diamine, was used as a biocatalyst for sulforaphene production. The overall hydrolysis ratio of glucoraphenin was 93.25 ± 0.91% and the activity of DDMCCR-IMYR remained 95% after 10 days of continuous use.

Adsorption of chromium(VI) from aqueous solution by glycine modified cross-linked chitosan resin

The adsorption of Cr(VI) onto glycine-modified crosslinked chitosan (GMCCR) resin has been investigated. Batch experiments were performed to examine kinetics, adsorption isotherm, pH effect, and thermodynamic parameters. The effect of pH for the adsorption of Cr(VI) was studied at range from 2 to 6 and the equilibrium was accomplished within 150 minutes and maximum removal was achieved under the optimum conditions at pH 3 . The result obtained from equilibrium adsorption studies are fitted Langmuir and Freundlich adsorption models and the data was found that the equilibrium data agreed very well with the Langmuir model . The maximum uptake was found to be 1.5 mmol/g (calc 1.75 mmol/g) at 250C. Thermodynamic parameters for the adsorption system were determined at 298 K, 308 K and 318 K (ΔH° =22.85 kJ•mol−1；ΔG° = −33.17 to −36.93 kJ•mol−1 and ΔS° = 188 J•K−1•mol−1). The positive values of ΔH° and ΔS° suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. The negative values of ΔG° indicating a spontaneous adsorption process. The kinetic process was described very well by a pseudo-second-order rate equation.

English

Sulfonated crosslinked chitosan resins (SCCRs) were prepared by firstly crosslinking chitosan to crosslinked chitosan resins (CCRs) using a reverse emulsion crosslinking method, followed by sulfonating CCRs with concentrated H 2 SO 4 as the sulfonation agent. The properties and application of SCCRs as solid acid catalysts were studied. The acidic sites in SCCRs, including C 6 –O and C 2 –N sulfate groups, are all weak acidic sites. SCCRs of higher crosslinking degrees have a higher sulfonation rate of the C 6 primary hydroxyl groups, thus more C 6 –O sulfate groups. High-temperature treatment and TG analysis verified that the crosslinking can improve the thermostability of both SCCR backbone and its acidic groups, and a higher crosslinking degree leads to better thermostability. Catalytic esterification of citric acid with butanol and propionic acid with n-butyl alcohol demonstrated that SCCRs have good catalytic activity and can be repetitively used as efficient solid acid catalysts.

Effective biosorption of patulin from apple juice by cross-linked xanthated chitosan resin

In this work, cross-linked xanthated chitosan resin (CXCR) was prepared by inverse suspension cross-linking method, using glutaraldehyde as cross-linking agent and carbon disulfide as modification agent. The biosorption of CXCR for patulin from apple juice was investigated. Batch adsorption experiments were performed to evaluate the effect of pH, temperature, contact time and initial concentration. The adsorption of CXCR for patulin was characterized by Fourier Transform Infrared Spectroscopy (FTIR). The results showed that the optimum adsorption conditions of CXCR for patulin was achieved at pH 4, 30 °C for 18 h. The adsorption data could be fitted with pseudo–second order kinetic model and Freundlich isotherm model. It indicated that CXCR is an appropriate adsorbent for the removal of patulin from apple juice.

Adsorption of Au(III) ions on xanthated crosslinked chitosan resin in hydrochloric acid medium

Xanthated crosslinked chitosan (XCCS) resin prepared under microwave irradiation were used for adsorbing Au(III) ions in hydrochloric acid medium. The influence of pH and temperature on the adsorption capacity of XCCS was investigated. The original XCCS and the loaded XCCS were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The results indicate that the XCCS has ability to adsorb Au(III) ions and the maximum adsorption capacity of Au(III) ions on XCCS is observed at pH 1 and 20 °C. The data of batch adsorption tests are fitted to kinetic models and isotherm models, respectively. The kinetics of adsorption process is found to follow pseudo-second-order kinetic rate model, and equilibrium data agree very well with the Langmuir model. Thermodynamic calculation of the Au(III) ions adsorption process indicates that the adsorption process is spontaneous and endothermic.

High Selective Separation of Flavonoids based on Crosslinked Chitosan Resin Grafted by Quercetin

In this study, crosslinked chitosan resin grafted by quercetin (QCCR) was used as a novel adsorbent to separate flavonoids. Functional quercetin groups were introduced to the adsorbent matrix, and the hydrophobic interaction occurred when these functional groups in the adsorbent approached the adsorbate with the same ring structure, which enhanced the adsorption selectivity towards flavonoids. The hydrophobic interaction played an important role in the selective adsorption. Atomic force microscopy provided intuitively the spatial conformation and the interactions between flavonoids and QCCR at the molecular level. The influences of functional groups of synthesized adsorbents on the adsorption selectivity and the optimum conditions were investigated in detail. QCCR was considered as an alternative material for obtaining the bioactive flavonoid compounds with high concentration.

Adsorption of congo red by cross-linked chitosan resins

In this study, cross-linked chitosan resins were prepared through inverse suspension and were used to adsorb congo red (CR). FT-IR spectra and SEM technique characterized the chitosan resins. The influences of contact time, temperature, adsorbent dose, initial concentration of CR, and pH of CR solution on the adsorption behavior were investigated. The results showed that the chitosan beads made from 5% chitosan in 2% aqueous acetic acid had smooth surface and strong mechanical strength. When the contact time was 60 min, temperature was 50°C, adsorbent dose was 0.02 g, initial concentration of CR was 80 mg/L, and pH of CR solution was 7, the best adsorption capacity was obtained. The adsorption behavior can be fitted well by the Langmuir isotherm and also obeyed the pseudo-second-order kinetic expression. The intra-particle diffusion studies indicate that the diffusion step was not the only rate-limiting step. Thermodynamic studies illustrated that the adsorption reactions are exothermic and spontaneous in nature.

Studies on the co-immobilized GOD/CAT on cross-linked chitosan microsphere modified by lysine

Glucose oxidase (GOD) and catalase (CAT) were co-immobilized on a novel crosslinked chitosan resin modified by L-lysine. The immobilized system exhibited the best performance when the immobilization process was conducted at 4 degrees C for 3 h with GOD/CAT activity ratio of 1:18 and pH 7.0. Under the optimum pH 4.0 and temperature 40 degrees C, the enzyme system could achieve to the maximum conversion of glucose, which was 68.9%. Acidoresistance and thermotolerance of the enzymes were both strengthened. The Km of the co-immobilized enzyme system obtained in this study was 31.02 mM. The GOD enzyme immobilized in this system could maintain 94% of initial activity after the 12th operational cycle. 95.8% of initial activity was left after 50 weeks' storage at 4 degrees C. GOD achieved better performance in this new immobilized enzyme system due to its effective elimination of H2O2, which showed potential applications for various commercial uses. (C) 2013 Elsevier B.V. All rights reserved.

Efficient removal of ferric ions from aqueous medium by amine modified chitosan resins

The removal of ferric ions was carried out by using crosslinked chitosan resins immobilized with diethylenetriamine (DETA) and tetraethylenepentamine (TEPA) as active moieties. TEPA containing chitosan resin showed higher uptake capacity (3.2mmol/g) toward Fe(III) compared with DETA containing one (1.4mmol/g) at 25°C. Both kinetics and thermodynamic studies of the adsorption process were carried out. Thermodynamic data indicated that adsorption process is exothermic and spontaneous reaction, while the kinetic data indicated that the adsorption of Fe(III) by the investigated resins follows the pseudo second order kinetics. Breakthrough time, critical bed height and durability of resins were estimated from column studies. The critical bed height for the studied resins are 0.2 and 0.05cm at a flow rate of 1mL/min and column diameter of 1cm for DETA and TEPA containing resins, respectively. These parameters indicated that the resin containing TEPA has high efficiency for Fe(III) removal from aqueous media. Desorption of Fe(III) from the prepared resins was efficiently done using thiourea acidified with HNO3.

Chitosan resins synthesised by improved drop-sphere-forming method for Cr(VI) removal from aqueous solutions

An improved drop-sphere-forming (IDSF) method was applied to synthesise chitosan resin. Chitosan resin was synthesised by the self-made device and cross-linked with epichlorohydrin. The influences of concentration of chitosan-acetic acid solution, air flow, reaction time and the dosage of epichlorohydrin were investigated during synthesising. The satisfactory chitosan particles were prepared by chitosan-acetic acid solution (3%) under a controlled air flow of 0.6 m(3) h(-1), After 6 h of reaction at 80 °C with an epichlorohydrin dosage of 2 mL per 5 mL wet resin, the chitosan cross-linked resin has the best adsorption capacity. After 2 h of adsorption at pH = 3.0 and 25 °C with an adsorbent dosage of 2 g L(-1), the maximum adsorption capacity (112 mg g(-1)) was reached for an initial Cr(VI) concentration of 146 mg L(-1). Compared with other adsorbents, this synthesis method was simple and economic; moreover, the cross-linked chitosan resin can remove Cr(VI) efficiently.

Synthesis and properties of an insoluble chitosan resin modified by azamacrocycle copper(II) complex for protein hydrolysis

We reported the synthesis process and the proteolytic ability of a novel crosslinked chitosan resin modified by azamacrocycle copper complex (CMCR). Characterization of CMCR showed that the Cu(II)Cyclen complex had successfully bound to the resin matrix covalently. Its proteolytic activity toward peptide bonds was evaluated by investigating the hydrolysis of bovine serum albumin in heterogeneous media. The maximum-observed pseudo-first-order rate constant (kobs) was achieved under 60°C, pH 6.0, where protein was hydrolyzed into smaller peptides and amino acids confirmed by SDS–PAGE and ninhydrin reaction. The results indicated that the hydrolyzing efficiency delivered by CMCR was 4 × 105 times higher than that of spontaneous hydrolysis. CMCR also featured a desirable stability for chelating Cu2+ ions, which paved the way for its feasible recovery process and good reusability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci, 2013

Dual functional adsorption of benzoic acid from wastewater by biological-based chitosan grafted β-cyclodextrin

Removal of benzoic acid from industrial wastewater is important for the water treatment, and adsorption is an efficient treatment process. Chitosan and β-cyclodextrin (β-CD) are well investigated as feedstock for preparing polysaccharide-based toxic compounds removing adsorbents. In this study, chitosan grafted β-CD (CGC) was synthesized using glutaraldehyde as cross-linker in acidic aqueous solution. The successful grafting of β-CD onto chitosan was confirmed by FTIR and XRD. Compared with β-CD-epichlorohydrin copolymer (CDP) and cross-linked chitosan resin (CCR), CGC showed an excellent ability to adsorb benzoic acid. The CGC adsorption kinetics toward benzoic acid at 298.15K, and isotherms at varying temperatures were studied systematically. Kinetics of the adsorption process agreed well with the pseudo-second-order kinetic model, and the experimental data of equilibrium isotherms fitted well with Langmuir model (R2>0.99). Furthermore, thermodynamic parameters revealed the spontaneity and exothermic nature of the adsorption process. The adsorption–desorption of benzoic acid by CGC and other two commercial adsorbents were evaluated and compared in five cycles, demonstrating high regeneration efficiency of CGC. The reversibility of benzoic acid adsorption by CGC was further proved by column recycle test. Finally, the adsorption mechanism was proposed according to the inclusion behavior of β-CD toward benzoic acid as well as the electrostatic interaction between chitosan units and benzoic acid.

Cr(VI) adsorption on an improved synthesised cross-linked chitosan resin

An improved drop-sphere-forming method to synthesise chitosan resin was investigated as a possible means to remove Cr(VI) from wastewater. Epichlorohydrin was used to cross-link the resin to enhance its rigidity. The Cr(VI) adsorption capacity of the cross-linked chitosan was investigated under the influence of time, pH, temperature and the initial concentration of Cr(VI). The pH was found to be the main factor determining adsorption capacity. After 2h of adsorption at pH=3.0 and 25°C with an adsorbent dosage of 2gL−1, the maximum adsorption capacity was reached for an initial Cr(VI) concentration of 30mgL−1. The equilibrium adsorption experiments corresponded well with the Langmuir isotherm (r2>0.99). The pseudo-first-order and pseudo-second-orders were applied to describe the kinetics of the process. Compared with a pseudo-first-order kinetic model, the pseudo-second-order kinetic model exhibited a better correlation with the experimental data (r2>0.99).

Adsorption of Dyes from Acidic Wastewater by Crosslinked Chitosan Resin

A new low cost adsorbent crosslinked chitosan resin has been used to remove dyes from wastewater. The crosslinked chitosan resin was prepared using inverse suspension polymerization with methanal and epichlorhydrin (ECH) using pre-crosslinking and crosslinking techniques. As comparison, the adsoption ability of chitosan and activated carbon was also investigated.

Cu2+‐imprinted cross‐linked chitosan resin as micro‐column packing materials for online chemiluminescence determination of trace copper

The Cu(2+)-imprinted cross-linked chitosan resin was synthesized and the binding characteristic of the resin to Cu(2+) was evaluated. The prepared resin was packed into a micro-glass column and used as micro-separating column. The micro-separating column was connected into the chemiluminescence flow system and placed in front of the window of the photomultiplier tube. Based on the luminol-hydrogen peroxide chemiluminescence system, a flow injection online chemiluminescence method for determination of trace copper was developed and trace Cu(2+) in complex samples was successfully determined. The proposed method improved the shortcomings of chemiluminescence method's poor selectivity.

Preparation and Characterization of Formaldehyde Crosslinked Chitosan

Using formaldehyde as a crosslinking reagena novel cross-linked chitosan resin was synthesized by orthogonal. The resin material with good properties of sphericity and acidresistivity can be prepared under the optimal experimental conditions, which are found to be 1:6 for the ratio of chitosan and formaldehyde, 60°C for the temperature, 1 h for the reaction time, 640r/min for the stirring rate and 9 for the pH, and the cross-linking rate under the optimal conditions is 401.86%. SEM shows the surface morphology changes of raw materials and products; IR of the raw materials and products shows that the reaction occurs mainly on the amino and the hydroxyl of chitosan, and TG shows that the crosslinking reaction of chitosan can change its heat resistance.

Adsorption of chromium (VI) by ethylenediamine-modified cross-linked magnetic chitosan resin: Isotherms, kinetics and thermodynamics

The adsorption of chromium (VI) ions from aqueous solution by ethylenediamine-modified cross-linked magnetic chitosan resin (EMCMCR) was studied in a batch adsorption system. Chromium (VI) removal is pH dependent and the optimum adsorption was observed at pH 2.0. The adsorption rate was extremely fast and the equilibrium was established within 6–10 min. The adsorption data could be well interpreted by the Langmuir and Temkin model. The maximum adsorption capacities obtained from the Langmuir model are 51.813 mg g −1, 48.780 mg g −1 and 45.872 mg g −1 at 293, 303 and 313 K, respectively. The adsorption process could be described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved in the present case. Thermodynamic parameters revealed the feasibility, spontaneity and exothermic nature of adsorption. The sorbents were successfully regenerated using 0.1 N NaOH solutions.

Enhanced sorption of bisphenol A on α-ketoglutaric acid-modified chitosan resins by hydrophobic sorption of hemimicelles

In this paper, α-ketoglutaric acid-modified chitosan resins (KCR) were successfully prepared. The capacity of KCR as weak cation exchanger for sorbing bisphenol A (BPA) from aqueous solution was compared with crosslinked chitosan resins (CCR) with cetyl trimethyl ammonium bromide (CTAB) as the intermediary of BPA sorbed on sorbent. The BPA removal was found to be dependent on the initial pH, KCR/CTAB dosage, BPA concentration, and contact time. The isothermal data of BPA sorption on KCR was in well agreement with the Langmuir model, and the maximum sorption capacity ( Q m) of KCR for BPA was 30.67 mg/g. The BPA sorption process could be described by the pseudo-second-order rate kinetic model.

Pre-concentration and determination of trace uranium (VI) in environments using ion-imprinted chitosan resin via solid phase extraction

The uranyl-ion-imprinted and non-imprinted cross-linked chitosan resins possessing quinoline-8-ol moiety have been prepared. In all the cases, a significant imprinting effect was noticed on comparing percent extraction of uranium (VI). The resulting ion-imprinted resin was used for solid phase extractive preconcentration of uranium (VI) prior to its determination by spectrophotometry. Experimental variables that influence the quantitative extraction of uranium (VI) were optimized by both static and column methods. The retention capacity found for uranium (VI) was 218 mg g-1 of resin which is higher than the corresponding non-imprinted resins and other solid phase extraction sorbents possessing quinoline-8-ol moiety. The optimum pH range was 4.5-7.0. Uranium adsorbed was easily and quantitatively eluted with 1 mol L-1 HCl (10 mL) at a flow rate of 2 mL min-1. Interference studies showed a high tolerance of diverse ions and electrolyte species. The limit of detection was 2 µg L-1 and the dynamic linear range was 5-100 µg L-1. The accuracy of the developed method was tested with one uranium ore standard reference material. Furthermore, the proposed method was successfully applied for the determination of uranium in contaminated soil and sediment samples.