Lujie Zhang

Adsorption of an anionic azo dye by cross-linked chitosan/bentonite composite

In this study, cross-linked chitosan (CCS)/bentonite (BT) composite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction between chitosan and glutaraldehyde. CCS/BT composite was characterized by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analyses (TGA). Their adsorption characteristics were assessed by using an azo dye (Amido Black 10B) as a model adsorbate. The adsorption of Amido Black 10B onto the CCS/BT composite was found to be optimal at pH 2. The adsorption isotherm was well described by the Langmuir model and the maximum adsorption capacity was 323.6 mg/g at 293K and pH 2. Amido Black 10B adsorption kinetics followed a pseudo-second-order kinetic model. The calculated thermodynamic parameters showed that the adsorption of Amido Black 10B by CCS/BT composite was spontaneous and endothermic in nature.

Adsorptive removal of Cr(VI) from aqueous solutions by cross-linked chitosan/bentonite composite

Cross-linked chitosan/bentonite composite (CCB) was prepared, and characterized by Fourier transform infrared (FTIR) spectroscopy, BET surface area and pore diameter analyses, X-ray diffraction (XRD) patterns and thermal gravimetric analyses (TGA). The adsorption of hexavalent chromium Cr(VI) onto CCB as a function of adsorbent dosage, initial Cr(VI) concentration, solution pH, and contact time was investigated through batch experiments. The removal towards Cr(VI) decreased with increasing solution pH from 2 to 11 and initial Cr(VI) concentration, while it increased with increasing adsorbent dosage. The adsorption kinetic data of Cr(VI) on CCB were well described by the pseudo-second-order model. The equilibrium data were correlated by the Langmuir isotherm model. The maximum monolayer Cr(VI) adsorption capacity for CCB at pH 2 and 293 K was 89.13mg/g. The mechanisms for the adsorption of Cr(VI) on CCB at pH 2 may include electrostatic interaction and chemical interaction between CCB and Cr(VI) ions.

Removal of fluoride from aqueous solution using Zr(IV) immobilized cross-linked chitosan.

In the present paper, zirconium immobilized cross-linked chitosan (Zr-CCS) was reported for the adsorption of fluoride. Zr-CCS was synthesized by methods of membrane-forming and subsequent cross-linking reaction. Zr-CCS was characterized by FTIR, XRD, and SEM technologies. Batch adsorption experiments were performed to evaluate the adsorption capacity of Zr-CCS toward fluoride. The adsorption of fluoride onto the Zr-CCS favored at low pH values, and reduced in the presence of other co-anions. The adsorption equilibrium data had a good agreement with the Langmuir isotherm model, and the maximum adsorption capacity was calculated as 48.26mg/g for fluoride at 303K and natural pH (6.0). Thermodynamic parameters indicate that the nature of fluoride adsorption was spontaneous and endothermic. The adsorption mechanism of fluoride onto the Zr-CCS was controlled by chemical ion-exchange and electrostatic attraction between Zr-CCS and fluoride.

Utilization of cross-linked chitosan/bentonite composite in the removal of methyl orange from aqueous solution

A kind of biocomposite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction of chitosan with glutaraldehyde, which was referred to as cross-linked chitosan/bentonite (CCS/BT) composite. Adsorptive removal of methyl orange (MO) from aqueous solutions was investigated by batch method. The adsorption of MO onto CCS/BT composite was affected by the ratio of chitosan to BT and contact time. pH value had only a minor impact on MO adsorption in a wide pH range. Adsorption kinetics was mainly controlled by the pseudo-second-order kinetic model. The adsorption of MO onto CCS/BT composite followed the Langmuir isotherm model, and the maximum adsorption capacity of CCS/BT composite calculated by the Langmuir model was 224.8 mg/g. Experimental results indicated that this adsorbent had a potential for the removal of MO from aqueous solutions.

Adsorption of methyl orange (MO) by Zr (IV)-immobilized cross-linked chitosan/bentonite composite.

A Zr (IV)-immobilized cross-linked chitosan/bentonite composite was synthesized and characterized by Fourier transform infrared, field-emission scanning electron microscopy, and X-ray diffraction techniques. This composite was utilized for the removal of methyl orange (MO) from aqueous solutions. Effects of the loading amount of Zr (IV), initial pH value of MO solutions, adsorbent dosage, and contact time on MO adsorption were considered. The adsorption isotherm data were well described by the Langmuir model, and the maximum adsorption capacity was 438.6mg/g at 303K and natural pH. The kinetic data were well described by the pseudo-second-order model. The thermodynamic data showed that the adsorption process of MO was feasible, spontaneous, and exothermic in nature.

Adsorptive removal of methyl orange using enhanced cross-linked chitosan/bentonite composite

AbstractIn this study, the cross-linked chitosan/bentonite composite was treated further with concentrated HCl. The resultant composite was referred to as the enhanced cross-linked chitosan/bentonite (ECCS/BT) composite, which was characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy techniques. ECCS/BT composite was used as an adsorbent to remove an anionic dye, methyl orange (MO), from aqueous solutions by a batch method. Various conditions were evaluated, including acid treatment, the ratio of chitosan to bentonite, initial MO concentration, adsorbent dosage, solution pH, and contact time. The adsorption kinetics and equilibrium isotherms of MO by the ECCS/BT composite were studied using the pseudo-first-order and pseudo-second-order kinetic models as well as Freundlich and Langmuir isotherm models. The kinetic data followed the pseudo-second-order equation; the isotherm data were described by the Langmuir isotherm model and the maximum adsorption...

Adsorptive removal of Congo red from aqueous solutions using crosslinked chitosan and crosslinked chitosan immobilized bentonite

Batch experiments were executed to investigate the removal of Congo red (CR) from aqueous solutions using the crosslinked chitosan (CCS) and crosslinked chitosan immobilized bentonite (CCS/BT composite). The CCS and CCS/BT composite were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The removal of CR was examined as a function of pH value of CR solution, contact time, and inorganic sodium salt and ionic strength. The equilibrium data of CCS and CCS/BT composite agreed well with the Langmuir model. The adsorption capacities of CCS and CCS/BT composite at 298K and natural pH value were 405 and 500 mg/g, respectively. The kinetic data correlated well with the pseudo-second-order model. The adsorption of CR onto the CCS was mainly controlled by chemisorption while the adsorption of CR onto the CCS/BT composite was controlled by chemisorption and the electrostatic attraction.

Crosslinked quaternized chitosan/bentonite composite for the removal of Amino black 10B from aqueous solutions.

In this work, the crosslinked quaternized chitosan/bentonite composite was prepared by membrane-forming and cross-linking methods, and characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. Batch mode was adapted for the adsorption studies. The equilibrium data and kinetic data were well described by the Langmuir isotherm and the pseudo-second-order kinetic model, respectively. There was not much drop in adsorption capacity up to 5th regeneration cycle. The maximum monolayer adsorption capacity was obtained at 990.1mg/g at 298K and natural pH in terms of the Langmuir model. The high adsorption capacity was attributed to the strong electrostatic interaction as well as the valence forces through the sharing or exchange of electrons between dye molecules and this composite. The thermodynamic parameters indicated the adsorption of Amino black 10B by this composite was a spontaneous and endothermic process.

Simultaneous adsorption of phenol and Cu 2+ from aqueous solution by activated carbon/chitosan composite

A multifunction adsorbent was synthesized by incorporating AC into CTS, and the ratio of AC to CTS was 1/1. The resultant was called activated carbon (AC)/chitosan (CTS) composite. The simultaneous adsorption of phenol and Cu2+ from aqueous solution onto AC/CTS composite was investigated by a batch procedure. The adsorption processes for both Cu2+ and phenol obeyed the pseudo second-order kinetic model. Phenol was prone to be adsorbed more quickly as compared with Cu2+ when they coexisted in solution. The adsorption behavior of both phenol and Cu2+ followed the Langmuir isotherm. The maximum adsorption capacities of phenol and Cu2+ were 34.19 mg/g and 74.35 mg/g at 293 K, respectively. No obvious competitive adsorption existed between phenol and Cu2+.

Simultaneous adsorption of aniline and Cu2+ from aqueous solution using activated carbon/chitosan composite

AbstractA multifunction adsorbent, activated carbon (AC)/chitosan composite, was synthesized by incorporating AC into chitosan based on the ratio of AC to chitosan being 1/1. The simultaneous adsorption of aniline and Cu2+ from aqueous solution onto AC/chitosan composite was investigated by a batch procedure. These results showed that an adsorbent dosage of 0.3 g was appropriate, and a contact time of 210 min was convenient for reaching adsorption equilibriums for aniline and Cu2+. The simultaneous adsorption of aniline and Cu2+ was realized in a wide pH range. The adsorption process obeyed the pseudo-second-order kinetic model. The adsorption behaviors of aniline and Cu2+ followed Freundlich and Langmuir, respectively. No obvious competitive adsorption existed between Cu2+ and aniline.