Enzymatic bio-oxidation technology as novel approach for pretreatment of refractory sulfide ores

This study introduces an innovative low-temperature-adapted process, Enzymatic Bio-oxidation Technology, for recovering gold from refractory sulfide ores. By utilizing glucose oxidase immobilized on modified sawdust, the process enhances pyrite dissolution and gold liberation under suboptimal conditions for traditional bio-oxidation methods. Experiments demonstrated that citric acid carboxylation improved enzyme activity, achieving a maximum of 80 µmol/min at 1 wt% glutaraldehyde concentration, while hydrogen peroxide production peaked at 20–24 °C. Optimized bio-oxidation conditions—100 mM substrate, 5 g immobilized enzyme, 1 g/L Iron(II), and 20 % ore content—resulted in 89.2 % pyrite dissolution for high-grade gold ore sample (HGOS) and 73.4 % for low-grade gold ore sample (LGOS). Subsequent cyanidation achieved maximum 91 % gold recovery within 20 h at pH 10–11, with HGOS exhibiting superior recovery of gold. These results underscore a promising, low-temperature bio-oxidation strategy for sustainable and efficient gold recovery from refractory ores, especially in environments where conventional microogranisms-assisted methods fall short.