[Cu2+ biosorption by bacterial alginate extracted from aerobic granules and its mechanism investigation]

The biosorption characteristic of copper ions onto dried Ca-alginate made of bacterial alginate extracted from aerobic granules was investigated in batch system. The biosorption rate of Cu2+ onto the alginate, effects of pH and alginate dosage on Cu2+ biosorption capacity and adsorption isotherm were analyzed. The biosorption of Cu2+ onto the dried Ca-alginate was a rapid process. The maximum Cu2+ uptake was 67.67 mg/g at pH 4, initial Cu2+ concentration of 100 mg/L, dried Ca-alginate dosage 0.7 g/L. Accumulation of Cu2+ followed Langmuir and Freundlich adsorption isotherm. Cu2+ adsorption was accompanied by Ca2+ releasing from the dried Ca-alginate and H+ uptake, indicating that the ion exchange between Cu2+ and Ca2+ requires H+ for charge balance. FT-IR secondary derivative spectra and atomic force microscopy analysis gave proof that, the reaction of MG blocks in dried Ca-alginate with Cu2+ and Ca+ were different. Cu2+ may form complex with MG blocks, leading to a much more ordered structure on the surface of the dried Ca-alginate. The dried Ca-alginate bio-adsorbent was regenerated by 100 mmol/L HCI with 91% Cu2+ recovery.