Electrowinning studies for metallic zinc production from double leached Waelz oxide

Waelz oxide is a zinc and lead concentrate pyrometallurgically derived from electric arc furnace dust. There are clear incentives to leaching and purify this oxide to produce liquors that can be electrowinned to obtain recycled metallic zinc. This study is focused on this electrolytic zinc production from previously obtained sulphuric liquor. This liquor was obtained from double leached Waelz oxide (DLWO) throughout a hydrometallurgical process. The electrolytic liquor, after the corresponding leaching and purification stages, contains around 49 kg/m3. This liquor was fed to an electrowinning process where platinum or lead anodes and aluminium cathodes were used. After optimizing the different electrowinning critical parameters, and working at these optimal conditions, almost 88 secondary zinc kg were precipitated per each initial DLWO tonne in one-through process. The zinc purity was higher than 99.5%. After some mass balance calculations, it can be concluded that, optimizing the process configuration through internal recycling, around 210 Zn kg/DLWO t with purity near to 100% could be achieved.

► Liquors from WO acid leaching can be treated to obtain metallic Zn by electrolysis. ► The most important parameters for the electrowinning of these liquors were found to be 4.5 V and 180 min. ► Operating under these conditions allowed at lab-scale zinc purities >99.5%. ► The conceptual design of a new process able to recover 210 kg metallic Zn/t of WO was presented. ► The economic value and improved environmental impact of the process as alternative to the conventional method.