Enhanced decolorization of aqueous dye solutions by a high quality copolymer flocculant

Abstract

A high quality copolymer (CATCS) based on starch and chitosan was synthesized and applied for the enhanced decolorization of aqueous dye solutions. The flocculant was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of the initial pH, dosage of CATCS, initial dye concentration, salt concentration and reaction time on the decolorization ability of CATCS were studied. An ultrahigh decolorization efficiency (97.1–99.7%) for the dye solutions was observed for CATCS. It was effective in a wide pH range (2 to 10) and could withstand a high salt concentration. The CATCS flocculant was ten times more efficient than commercial activated carbon in the treatment of real dye wastewater. A decolorization efficiency of 98.3% for the real dye wastewater was reached using 0.34 g L⁻¹ CATCS. The thermodynamics and kinetics of the decolorization process were investigated in detail and the decolorization mechanism with CATCS was determined. The enthalpy change was over 41 kJ mol⁻¹ for the decolorization process of dye solutions by CATCS. The positive entropy change value for the decolorization corresponded to an increase in the degree of freedom of the adsorbed species. The decolorization process was endothermic and the interaction was controlled with chemisorption.