Selective extraction of arsenic and antimony from gold-bearing sludge using two-stage alkaline leaching

Abstract In gold smelting industry, coexisting of arsenic (As) and antimony (Sb) in gold-bearing sludge is a serious issue for the smelting process. This study employed a two-stage leaching methods to selective extract arsenic and antimony from gold-bearing sludge. Arsenic was firstly removed through NaOH leaching, following by Na2S-NaOH leaching to remove antimony in the atmospheric conditions. The first step results show that more than 96% of arsenic can be removed under the conditions of 2 mol/L NaOH, the ratio of liquid to solid (L/S) of 5, 60 °C, 400 rpm, 3 h. Meanwhile, the antimony dissolved in the solution is converted into the residue as the state of NaSb(OH)6 during this process. After Na2S-NaOH leaching, the antimony leaching extent is 97.2% during the condition of 2.5 mol/L Na2S, 0.125 mol/L NaOH, L/S = 5, 70 °C and 6 h. In addition, the vulcanization of copper was found in the Na2S-NaOH leaching process, and the CuS appeared in the leaching residue. The results prove that the NaOH leaching following by Na2S-NaOH leaching can selectively extract arsenic and antimony from gold-bearing sludge in the atmospheric conditions.