Kinetic and thermodynamic evaluation of adsorption of Cu(II) by thiosemicarbazide chitosan.

A modified biomacromolecule, chitosan-thiosemicarbazide framework (TSCS) as an adsorbent for Cu(II) was prepared from dialdehyde chitosan through condensation reaction with thiosemicarbazide, stabilized by the reduction reaction with sodium borohydride. TSCS was characterized by means of FT-IR and XPS. Surface morphologies were studied by FESEM and BET, which revealed the highly macro porous structure. The thermal analyses was done through TGA showing much stable chemical configuration at about ≥400°C. The experimental equilibrium data was evaluated by Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The Langmuir adsorption model was best fitted with experimental value, suggests the existence of monolayer coverage of adsorbed molecules with a maxima of 142.85mgg(-1). The kinetic data was analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models and the pseudo-second-order kinetics were found for all the concentrations. The calculated thermodynamic parameters such as ΔG(o), ΔH and ΔS were -2.33kJmol(-1), 570.40Jmol(-1) and 9.75Jmol(-1)K(-1) respectively signifies the adsorption of Cu(II) onto TSCS is endothermic, spontaneous and a process of physisorption. The regeneration efficiency of the TSCS as an adsorbent was found to be ≥90-95% using 0.1M EDTA.