Two-stage chemical-biological oxidation process for low-grade refractory gold concentrate with high arsenic and sulfur

Abstract

In order to cost-effectively exploit and utilize the low-grade refractory gold ore resource with high arsenic and sulfur and reuse the ferric iron resources remained in the bio-oxidation waste solution, a two-stage oxidation process combining secondary high-temperature oxidation of the bio-oxidation solution with subsequent bio-oxidation was proposed for treating such resource. Scanning electron microscopy and laser particle sizer were used to analyze the oxidized residue, and the results demonstrated that the material surface was destroyed and the particle specific surface area was increased accordingly. Moreover, chemical analysis revealed that the nitrogen element content in concentrate was also increased greatly after oxidation. As a result, microbial adsorption behavior and growth rate were significantly improved and accelerated in the bio-oxidation stage. Specifically, 16S rRNA gene analysis indicated that the activity and proportion of iron-oxidized microorganism Leptospirillum genus in community was improved obviously after chemical oxidation. Therefore, the bio-oxidation efficiency of the concentrate was significantly increased in this stage. Consequently, the extraction levels of As, Fe and S elements in this process were 97.9 ± 0.9 %, 71.5 ± 4.8 % and 64.3 ± 1.6 % respectively, which were significant increased by 30.8 ± 0.8 %, 40.2 ± 1.6 % and 35.6 ± 3.8 % compared to the values in one-stage bio-oxidation. In the meantime, the gold and silver extraction yields by cyanidation in this process were increased from 61.5 ± 1.0 % and 58.1 ± 1.2 % of one-stage bio-oxidation process to 92.2 ± 1.2 % and 89.8 ± 2.8 %, respectively.