Sorption Properties of Chitosan in the Refining of Rough Indium

Abstract

The degree of purity of cathode deposits during the electrochemical refining of rough indium depends on the content of impurity metals in the electrolyte. In this work, an additional sorption purification of the refining electrolyte was carried out in order to reduce the content of such impurity metals as cadmium, lead, copper. Chitosan was used as a sorbent due to high sorption properties with respect to heavy metal ions. The determination of the concentration of the studied metals before and after the sorption was carried out by the method of differential pulse anodic stripping voltammetry (DPASV). The experimental results allowed to calculate the amount of metal sorbed by chitosan and the efficiency of its removal. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined. The Langmuir model agrees very well with experimental data. An inductively coupled plasma optical emission spectroscopy (ICP-OES) method was used to determine the presence of impurity metals and the degree of purity of electrorefined indium. The use of chitosan as a sorbent in the purification of rough indium allows to reduce the concentration of impurity metals in cathode deposits and to increase the content of the base metal to 99.9994%.