Water leaching of arsenic trioxide from metallurgical dust with emphasis on its kinetics

Abstract

Water leaching of As2O3 from metallurgical dust containing various metals was investigated, serving the purpose of dearsenization and simultaneous metal enrichment especially for indium. Effects of leaching temperature, liquid/solid ratio (LSR) and leaching time were studied. It was found that the initial dissolution was very fast but was then so inhibited by the increasingly dissolved As2O3, which makes it difficult to saturate enough arsenic in the leaching solution or in leaching out all the soluble arsenic with excess dosage of water within acceptable time (120 min). Only about 73% of As2O3 was extracted under the optimal conditions investigated. Two-step leaching showed similar trends and was thus unnecessary for improving As2O3 extraction. These observations could reasonably be accounted for the reversibility of the dissolution reaction. Kinetically, the leaching was described satisfactorily by the semi-empirical Avrami model with the apparent activation energy of 36.08 kJ/mol. The purity of the obtained product AS2O3 could reach 98.7%, while the indium could be enriched in the leaching residue without loss.