Environmentally Friendly and Energy-saving Anode for Nonferrous Metal Electrowinning Operating through the Liquid-Liquid Phase Separation

Abstract

Lead-silver alloys have been extensively used as anode material for the nonferrous metal electrowinning. However, it is inevitable that the harmful elements like Pb detaches from the anode and concentrates in the anode slime, electrolyte and cathode. The precaution and reduction of lead pollution is a challenging event. Here we successfully design and manufacture Pb-Ag-Al alloy anode which poses excellent performances on synergistic inhibition of lead dissolution and reduction of harmful pollutants during the zinc electrowinning process. Compared to the Pb-1wt.%Ag alloy anode, the formation rate of anode slime reduces by about 90.8%, and the lead contents in zinc product and electrolyte decreases by about 59.8% and 4.5% when the Pb-1wt.%Ag-0.15wt.%Al alloy is serviced as anode after 168 h. Besides, the anodic potential of Pb-1wt.%Ag-0.15wt.%Al alloy diminishes by about 3.6% and the generation amount of cathode product increases by about 9%. The underlying mechanism of Al addition were clarified in-depth. It indicates that a thin and dense Al2O3 protective film forms during zinc electrodeposition process when the Pb-Ag-Al alloy is used as anode material, which is responsible for the reduction of hazardous pollutants. The low anodic potential is attributed to the formation of spherical or nearly spherical Ag2Al phase. Our work not only provides a new strategy for the manufacture of environmentally friendly and energy-saving Pb alloy anode, but also promotes the improvement of the product quality.