Removal of scorodite arsenic from gold ore in the form of AS2S3 and AS4S4

Abstract

This paper discusses the removal of arsenic scorodite from the gold ore. Kinetic studies on the possibility of removal of arsenic in a compact shape of arsenic sulfide were carried out, which occupies a small volume. The reagent reaction order and activation energy are calculated. The limiting stage of the process occurred in the intradiffusion region, i.e. the rate of the process limits the diffusion supply of the reagent to the reaction boundary (or removal of products from it) through a layer of a solid substance (hematite-Fe2O3), formed during the sulphidization roasting, which is one of the decomposition products of scorodite. The reactions of decomposition of scorodite with the formation of arsenic sulfides are proposed, and the process of their progress confirmed by thermodynamic calculations and chemical analysis. The results of testing of sulphidization roasting on the gold-bearing refractory ore are presented, in which arsenic is mainly concentrated in scorodite. It was found that the recovery of arsenic in the form of As2S3 and As4S4 in sublimates is 92.1%. Comparative studies on the cyanidation of oxidized scorodite gold-containing ore and the cinder of sulphidization roasting were carried out. The industrial application of this technology provides an environmentally safe and efficient processing of such refractory gold-containing ores. The results show that sulphidization roasting increased the degree of gold recovery from 80% to 93.5% when the cyanide concentration increased from 1 kg/t to 1.75 kg/t.