Evaluation of ferric ion reductants in sulfate based copper electrowinning electrolyte

In order to improve energy efficiency and avoid acid mist an alternative anodic source of oxidation of ferrous ions has been proposed as an alternative to water hydrolysis in the conventional copper electrowinning process. However, because ferrous ions are converted to ferric ions at anode, there is a need for reduction of ferric ions to ferrous ions to facilitate an acceptable overall process. In this study sulfur, mineral sulfides, sulfur dioxide and hydrogen were studied since these were found to carry out the reduction without introducing any impurities in the solution, which may affect the actual electrowinning process. The performance of these compounds was evaluated in relation to overall process requirements.