Recovery of alkali, selenium and arsenic from antimony smelting arsenic-alkali residue

Arsenic-alkali residue is a hazardous waste produced by the refining process of crude antimony in antimony smelting, and contains highly toxic sodium arsenate and a large number of residual alkali. In this study, aiming at the problems of the low recoveries and incomplete separation of arsenic and alkali, the secondary pollution of arsenic-alkali mixed salts and the insufficient utilization of valuable resources in the treatment process of arsenic-alkali residue, a new process of antimony enrichment with water leaching, twice alkali recovery with CO2, selenium recovery with acidification and arsenic recovery with SO2 reduction and evaporation concentration was proposed to dispose arsenic-alkali residue. The results showed that the leaching efficiencies of Sb, As, Se and alkali in arsenic-alkali residue were 1.8, 98.4, 97.9 and 100% by hot water leaching, respectively. Alkali was recovered with CO2 from arsenic-alkali solution and the direct recovery was 87.8%. In addition, the purity of Na2CO3 product was higher than 90% and As content in product was controlled below 0.2%. Deep alkali removal and efficient selenium recovery were achieved by acidification from the solution after alkali recovery, the direct recovery of Se was 80.6%, and the purity of crude selenium was 81.7%. Arsenic was recovered from the solution after selenium removal and the direct recovery was 79.4%, and the quality of As2O3 product reached the third grade standard of arsenic trioxide (GB 26721-2011). This process realizes the efficient recovery of alkali, selenium and arsenic in arsenic-alkali residue, and also does not produce arsenic-alkali mixed salts and wastewater. (C) 2019 Elsevier Ltd. All rights reserved.