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Abstract In this study, the removal effect of arsenic(V) was compared with different lead-containing substances, and the process of arsenic(V) removal with lead oxide was optimized. The results showed that As(V) removal efficiencies with lead powder, lead oxide, lead hydroxide and lead nitrate were 26.5%, > 99.9%, 98.5% and 96.3% at lead/arsenic(Pb/As) molar ratio of 2.12, respectively. Arsenic(V) removal with lead and its compounds was mainly based on the formation of mimetite. The removal of arsenic with lead oxide did not introduce impurity anions, and the crystallization performance and stability of the precipitate were relatively better than those of the precipitates obtained with other lead-containing substances. The crystallization performance of the precipitate was obviously improved when lead oxide was added twice. Using pH-conditioning in the process of arsenic removal, the residual lead in the solution could be removed via the co-precipitation of the hydrolysis of Pb2+ with mimetite. The highest As(V) leaching concentration of As—Pb precipitates was 0.2 mg/L at the pH of 1.9–12.3 with the leaching time of 1–48 h, and the stability of As—Pb precipitates could be improved by washing with dilute nitric acid. Lead oxide could be used as an effective reagent of arsenic removal in aqueous chloride solution. Highlights • Removal effect of arsenic(V) was compared with different lead-containing substances. • Arsenic(V) removal with lead oxide did not introduce impurity anions. • Stability of precipitates was improved by changing the addition ways of lead oxide. • The residual lead was removed by pH-conditioning in the process of arsenic removal. [ABSTRACT FROM AUTHOR]

• A combined process was proposed to purify crude As 2 O 3 and prepare high-purity As 2 O 3. • Above 95% As was extracted from crude As 2 O 3 by acidic oxidation leaching. • As(V) reduction process was controlled by both diffusion and chemical reaction. • The purification process is efficient and environmentally friendly. In this study, a combined process of acidic oxidation leaching and SO 2 reduction was proposed to purify crude As 2 O 3 recovered from antimony smelting arsenic-alkali residue. The effects of various process factors on crude As 2 O 3 leaching were investigated based on the thermodynamic analysis. The results showed that the leaching efficiency of arsenic was 95.5% when crude As 2 O 3 was leached with the mixed solution of H 2 SO 4 and H 2 O 2 under the conditions: the H 2 O 2 /As(III) molar ratio (n (H 2 O 2): n (As(III))) of 0.93, leaching temperature of 75 ℃, leaching time of 90 min and liquid-solid ratio of 4:1. The kinetic study of As(V) reduction with SO 2 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 16.69 kJ mol−1. Arsenic could be directly recovered in the form of As 2 O 3 from leaching solution by SO 2 reduction, and the obtained product reached the standard of As 2 O 3 -1 (GB 26721-2011) after further purification. The direct recovery of arsenic was 85.8% after twice purifications for crude As 2 O 3. In addition, no arsenic-containing wastes were produced in the purification process. Overall, this process is efficient and clean for the purification of crude As 2 O 3. [ABSTRACT FROM AUTHOR]