A Process for the Production of Zn Powder by Alkaline Treatment of Brass Smelting Ash at Industrial Scale

In this paper, an industrial-scale alkaline process for the production of Zn powder using brass smelting ash as raw material was presented. It was suggested that the brass smelting ash be leached with 230 g/L NaOH solution at 80degC for 90 min at a phase ratio of 15. The maximum extraction of Zn and Pb can be reached at 96-99% and 90-95%, respectively. After Pb was separated selectively and quantitatively by sodium sulfides precipitation, the solution was subjected to electrolysis for the production of zinc powder with a current density of 800-1000 A/m² at 40-50degC, using stainless steel electrodes as anode and titanium alloy as cathode. The specific energy for the Zn electrolysis was around 2.7-3.1 kWh/kg Zn. Additional operations including Zn powder filtration, washing, desiccation, sieving and milling etc. were required, and the production of Zn powder with a purity over 96% can be obtained finally. Compared with the classical acidic-air pulverization production process of Zn powder, about 10-15% energy can be saved by the alkaline process.