Cross Linking-cyanoethylation for Chitosan Polymer for the Removal of Cr(III) and Co(II) Using Batch and Fixed Bed Column Methodsx

Abstract

Modified chitosan was prepared by reaction of cross-linked chitosan beads (CLCB) with acrylonitrile via cyanoethylation reaction of amino group which supports chitosan with nitrile groups, then the resulting cyanoethylated chitosan beads (CECB) were converted to chitosan-amidoxime chelating resin (CACR) via reaction with hydroxylamine hydrochloride. The resulted chelating resin was in the form of beads in order to be easy to capture heavy metals from water. Characterization was made using FTIR Spectroscopy, thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), BET surface area, and scanning electron microscope (SEM). The adsorption of cobalt and chromium from aqueous solution onto CACR has been investigated as a function of pH, metal ion concentration, contact time, metal ion concentration and temperature. Adsorption experiments indicated that the adsorption capacity was dependent on operating variables which are minimally (47.84, 50.68mg/g) and maximally (600, 147.33 mg/g) for Cr(III) and Co(II) respectively. Results revealed that CACR has high affinity toward Co(II) and Cr(III) ions. The saturated adsorption capacities at 25°C were 147.33 and 600 mg/g resin for Co(II) and Cr(III), respectively. Equilibrium isotherm data were analyzed using Langmuir, Freundlich, and Temkin isotherm models for Co(II) and Cr(III). The adsorption was well fitted by Langmuir isotherm model for Co(II) and Cr(III). The kinetic data indicated that adsorption fitted well with the pseudo-second-order kinetic model for Co(II) and Cr(III). Equilibrium distribution coefficient was obtained at different temperatures Thermodynamic parameters showed that the sorption is endothermic, spontaneous and contributes to increase ∆S of the system. The adsorption performance of CACR toward Co (II) and Cr(III) using fixed bed column method was investigated under different conditions. Mathematical models of Adams–Bohart, Thomas and Yoon–Nelson were applied to the experimental data to analyze the column performance. The results fitted well to the Adams–Bohart, Thomas and Yoon–Nelson models.