The removal of lead from aqueous dilute solutions by complexation-ultrafiltration with chitosan was studied. Experiments were performed as a function of aqueous pH, chitosan/Pb2+ ratio, and background electrolyte concentration. The value of pH was found to be the most important parameter to effect the lead removal. The lead removal rate reaches the plateau at almost 100% when the chitosan and lead ratio goes more than 4.0 at pH 6.0. With transmembrane pressure (TMP) 0.1 MPa, chitosan/Pb2+ ratio 4 and pH 6, the lead removal rate decreases sharply from 99.2% to 19.5% as the adding NaCl concentration increases from 0 to 500 mmol. The regeneration of the chitosan by acidification using diafiltration technique was further performed. In the end, the effect of regenerated chitosan on the lead removal was evaluated. At the optimum experimental condition of pH 6.0, regenerated chitosan/Pb2+ ratio 4 and TMP 0.10 MPa, the lead removal rate was found to be 96.2%, which is almost the same as that obtained on the original chitosan. The overall results from the two-step process of complexation-UF and decomplexation-UF separation showed that it could be a promising method for lead removal and recovery from aqueous solutions.
Keywords: chitosan, complexation-ultrafiltration, decomplexation-ultrafiltration, diafiltration, lead removal