Removal of Cu(II) from aqueous solutions using chemically modified chitosan

Abstract

Chemically modified chitosan namely epichlorohydrin cross-linked xanthate chitosan (ECXCs) has been used for the removal of Cu(II) ions from aqueous medium. The influence of various operating parameters such as pH, temperature, sorbent dosage, initial concentration of Cu(II) ions and contact time on the adsorption capacity of ECXCs has been investigated. Thermodynamic parameters namely G◦, H◦ and S◦ of the Cu(II) adsorption process have been calculated. Differential anodic stripping voltammetric technique was used to determine the concentration of Cu(II) in the test solution before and after adsorption.Thenatureofthepossibleadsorbent–metalioninteractionswasstudiedbyFouriertransform infrared spectroscopy and X-ray photoelectron spectroscopy. The studies showed that the adsorption of Cu(II) on ECXCs strongly depends on pH and temperature. The maximum adsorption capacity was observed at pH 5.0 and the adsorption capacity of ECXCs increased with increasing temperature indicating the endothermic nature of adsorption process. Langmuir and Freundlich adsorption equations were used to fit the experimental data. The adsorption process is found to follow the pseudo-secondorder kinetic model. Themaximumadsorptioncapacitywasfoundtobe43.47mgg−1 fromtheLangmuir isotherm model at 50◦C. During desorption studies 97–100% of adsorbed copper ion is released into solution in presence of 1N EDTA, HCl and H2SO4.