Separation and recovery of arsenic from arsenic-bearing dust

A hydrometallurgical process, including selective extraction, As-precipitation, the insoluble and sodium removal, acid dissolution and recovery of arsenic trioxide, was developed to treat arsenic-bearing dust. Arsenic was selective extracted by a mixed NaOH-Na2S leaching system with 2.5 mol/L NaOH and 0.2 mol/L Na2S. In this system, more than 90.0% As was extracted, while Sb and Pb were precipitated in residue as NaSb(OH)6 and PbS. Based on the solubility of As2O5, a method for precipitating arsenic in the form of sodium arsenate from alkaline leachate by oxidization-precipitation was established. Then, the sodium arsenate was converted to Ca-As compound by adding exceeding CaO into sodium arsenate solution. H3AsO4 solution, prepared by dissolving Ca5(AsO4)3OH in dilute H2SO4, was further reduced to HAsO2 by H2SO3 and then reduction solution was concentrated and crystalized as octahedral shaped As2O3. This process transformed the hazardous material to valuable material and realized the resource recycling of arsenic.