Process and mechanism investigation on comprehensive utilization of arsenic-alkali residue

Arsenic-alkali residue is a solid waste produced by the antimony smelting industry, which can pose a threat to the environment and human health. The common wet treatment process of arsenic-alkali residue has a low recovery of valuable elements, incomplete separation of arsenic and alkali, and also produces arsenic-alkali mixed salt, which cannot realize the completely harmless treatment of arsenic-alkali residue. In order to solve these problems, the oxidative water leaching process was used to treat arsenic-alkali residue, which realized the separation of arsenic and antimony. The leaching efficiencies of arsenic and antimony were 91.79% and 0.62%, respectively. The leaching residue could be returned to the antimony smelting system to recover antimony. Then the arsenic and alkali were directly separated from the arsenic-alkali mixed salt by carbothermal reduction, and 98.3% of arsenic was removed, and the non-toxic metallic arsenic with 99.9% purity was prepared. The alkali could be recovered from the slag after reduction, which solved the problem of harmless and recycling treatment of arsenic-alkali mixed salts. The mechanism of arsenic reduction pathway was studied through thermodynamic, phase, and arsenic valence state analyses.