Recovery of ultra-trace palladium using chitosan and its sulphur-containing derivative in HCl medium

Sulphur-containing chitosan, a water-soluble derivative of chitosan, was synthesized by using chitosan and other reagents. This sulphur-containing chitosan was combined with chitosan to recover ultra-trace palladium in HCl medium. The effects of the chelating dosages, pH, chelating precipitation rate, initial Pd concentration and coexisting cations were systematically investigated via chelating precipitation experiments. Under the optimized conditions, greater than 95% of palladium was recovered from the HCl medium, with pH ranging from 2 to 5.5 and proper dosages of chitosan and sulphur-containing chitosan, which were related to the concentration of Pd(II) ions. In addition, the presence of coexisting cations (Cu2+, Ni2+, Fe2+, and Sn2+) had no effect on the recovery rate of palladium. The recovery mechanism of palladium by chitosan and sulphur-containing chitosan was studied via molecular weight analyses, elemental analyses, FT-IR analyses and XPS analyses. The proposed chelating precipitation method was successfully applied to the recovery of ultra-trace palladium in HCl medium.