Fabrication of a copolymer flocculant and application for Cr(VI) removal

A copolymer flocculant (CATCS) derived from starch and chitosan was fabricated and used as eco-friendly adsorbent for removal of Cr(VI) from aqueous solution. The CATCS flocculant was characterized by scanning electron microscope, thermogravimetic analysis, and Fourier transform infrared spectroscopy. The effects of CATCS dosage, initial Cr(VI) concentration, pH, and reaction time on removal of Cr(VI) were discussed. The results showed CATCS removed Cr(VI) effectively and the adsorption isotherm agreed well with the Freundlich isotherm and R-P isotherm models. The enthalpy change (H) of the process was 16.75 kJ/mol suggesting the existence of chemisorption and the reaction was endothermic. Moreover, the negative free energy change (G) indicated the adsorption process was feasible and spontaneous. The positive entropy changorptione (S) showed there was an increase of disorder in the system during the adsorption process. The adsorption kinetics results showed that the ads could be described by the pseudo-second-order kinetics mechanism. The activation energy (E-a) of the adsorption reaction was 29.16 kJ/mol. POLYM. ENG. SCI., 56:1213-1220, 2016. (c) 2016 Society of Plastics Engineers