Environmentally benign utilization and arsenic stabilization in two–stage oxidation process of multiple refractory gold concentrate coated with carboniferous high arsenic sulfide

Abstract

To achieve efficient and environmentally benign utilization of carbonaceous high-arsenic refractory gold concentrates, a two-stage oxidation process combining bio-oxidation and suspension roasting was proposed. In the first stage, mixed aerobic mineralizing autotrophic bacteria were employed to oxidize sulfide minerals and remove arsenic and sulfur under controlled conditions. In the second stage, suspension roasting was applied to eliminate residual carbonaceous matter and further oxidize sulfides. Phase transformation, microstructure evolution, and pore characteristics were systematically analyzed using XRD, SEM-EDS, and BET techniques. The results show that bio-oxidation significantly enhanced gold liberation, increasing the exposed gold proportion from 4.27% to 56.56% and improving gold extraction from 15.42% to 30.17%. However, carbonaceous matter limits further improvement due to the preg-robbing effect. Subsequent suspension roasting at 550 °C for 45 min achieved a carbon removal rate of 99.38%, reduced carbon content to 0.028%, and increased exposed gold to 69.43%. As a result, gold extraction was markedly improved to 83.74%. Meanwhile, arsenic remained effectively stabilized in the roasted product, primarily as stable arsenate phases. These findings demonstrate that the proposed two-stage oxidation process effectively enhances gold recovery while ensuring arsenic stabilization and environmental compatibility, providing a promising strategy for the high-value utilization of multi-refractory gold resources.

Keywords

refractory gold ore / biological oxidation / suspension roasting oxidation / gold extraction / arsenic retention

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