Chlorine inclusion mechanism in high purity copper electrorefining from nitric acid system

A practical approach was introduced to study the inclusion mechanism of chlorine in high purity copper electrorefining from nitric acid system via cyclic voltammetry (CV) combined with electrodeposition experiments. The CV curves display an obvious reduction peak of CuCl intermediate, which can provide an insight into the electrochemical behaviour of this inclusion. Experimental results show that the increase of HNO3 concentration is favourable to reducing the quantity of chlorine inclusion although there is a slight decline in cathodic current efficiency. The optimum conditions for copper electrorefining in nitric acid system are HNO3 concentration in solution of 1−2 mol/l, moderate temperature of ca. 35 degrees C with current density not exceeding 25 mA/cm2. Based on the theoretical studies, an optimised copper electrorefining experiment was designed to simulate the industrial electrolysis, by which high purity copper can be obtained with chlorine inclusion less than 10 microg/g and current efficiency higher than 90%. (Authors.)
A practical approach was introduced to study the inclusion mechanism of chlorine in high purity copper electrorefining from nitric acid system via cyclic voltammetry (CV) combined with electrodeposition experiments. The CV curves display an obvious reduction peak of CuCl intermediate, which can provide an insight into the electrochemical behaviour of this inclusion. Experimental results show that the increase of HNO3 concentration is favourable to reducing the quantity of chlorine inclusion although there is a slight decline in cathodic current efficiency. The optimum conditions for copper electrorefining in nitric acid system are HNO3 concentration in solution of 1−2 mol/l, moderate temperature of ca. 35 degrees C with current density not exceeding 25 mA/cm2. Based on the theoretical studies, an optimised copper electrorefining experiment was designed to simulate the industrial electrolysis, by which high purity copper can be obtained with chlorine inclusion less than 10 microg/g and current efficiency higher than 90%. (Authors.)