Purification of crude As2O3 recovered from antimony smelting arsenic-alkali residue

Abstract

In this study, a combined process of acidic oxidation leaching and SO2 reduction was proposed to purify crude As2O3 recovered from antimony smelting arsenic-alkali residue. The effects of various process factors on crude As2O3 leaching were investigated based on the thermodynamic analysis. The results showed that the leaching efficiency of arsenic was 95.5% when crude As2O3 was leached with the mixed solution of H2SO4 and H2O2 under the conditions: the H2O2/As(III) molar ratio (n(H2O2): n(As(III))) of 0.93, leaching temperature of 75 ℃, leaching time of 90min and liquid-solid ratio of 4:1. The kinetic study of As(V) reduction with SO2 gas showed that the reduction process conformed to the first-order gas/liquid reaction kinetics, and was controlled by both diffusion and chemical reaction with an apparent activation energy of 16.69kJmol−1. Arsenic could be directly recovered in the form of As2O3 from leaching solution by SO2 reduction, and the obtained product reached the standard of As2O3-1 (GB 26721-2011) after further purification. The direct recovery of arsenic was 85.8% after twice purifications for crude As2O3. In addition, no arsenic-containing wastes were produced in the purification process. Overall, this process is efficient and clean for the purification of crude As2O3.