Selective removal of arsenic from high arsenic dust in the NaOH-S system and leaching behavior of lead, antimony, zinc and tin

This work investigated the selective removal of arsenic from a lead-antimony-zinc-containing high arsenic dust in alkaline solution. The effects of sodium hydroxide (NaOH) concentration, temperature, leaching time, liquid-solid ratio (L/S) and the presence of elemental sulfur on the dissolution of arsenic (As), antimony (Sb), lead (Pb) and Zinc (Zn) in NaOH solution were studied. The results show that the addition of elemental sulfur can effectively restrain the leaching of lead, antimony and zinc from high arsenic dust. Antimony trioxide (Sb2O3), arsenic trioxide (As2O3), basic lead arsenate [Pb-5(AsO4)(3)OH] and zinc arsenate [Zn-3(AsO4)(2)] in the raw materials were converted into sodium antimonate hydrate [NaSb(OH)(6)], lead sulfide (PbS) and zinc sulfide (ZnS). Arsenic existed in the leaching solution in the form of AsO33- or AsO43-. 99.8% of Arsenic was leached under the optimized conditions, while about 98.2% of antimony, 99.9% of lead and 99.8% of zinc remained in the leach residue with the arsenic concentration less than 0.1%. In addition, the kinetics of arsenic leaching from high arsenic dust was investigated, with the calculated apparent activation energy of 7.62 kJ/mol. The results show that arsenic leaching is a diffusion-controlled process in the solid film, and the solid film was inferred as the lead sulfide, zinc sulfide and sodium antimonate hydrate. This study provides an efficient, clean and environmental-friendly method for arsenic separation from high arsenic dust, together with recovering valuable metals. It is expected to be a promising alternative for recycling various As-Pb-Sb-Zn-containing complicated materials.