Abstract
| The zinc electrowinning process is a critical stage in zinc extraction, accounting for a substantial amount of a plant's power consumption. A significant portion of this powder consumption is due to the oxygen evolution reaction (OER) overvoltage of the conventional lead-based anodes. The use of Mixed Metal Oxides (MMO) anodes has emerged as a potential solution to improve energy efficiency and environmental sustainability, as they exhibit lower overpotential for OER. However, the efficiency of MMO anodes can be adversely affected by the deposition of MnO2 in typical zinc electrolytes, leading to increased cell resistance. In addition, other impurities present in industrial solutions can also affect the efficiency of these anodes. This study aims to investigate the long-term performance of MMO anodes on a pilot scale. The manganese has already been removed from the electrolyte to a level below the Mn2+ tolerance of the MMO anode. So, we focused on the effect of other typical impurities in the real-plant solution. To achieve this, an industrial plant solution was pre-treated with SO2/O2 mixture to achieve a Mn2+ concentration of 10 mg/L. Commercial MMO anodes were used to replace lead-based anodes. A decrease in current efficiency from 95% to 42% and an increase in cell voltage from 2.95 V to 3.2 V was observed compared to an impurity-free electrolyte. Our analysis showed that the reduction in current efficiency is primarily due to the presence of residual antimony in the solution. This residual amount was due to the non-proportional addition of potassium antimony tartrate during the cementation process in line with the conventional protocol for Co removal. |