Insight into the promotion mechanism of humic acid on arsenopyrite bioleaching mediated by Acidithiobacillus ferrooxidans

Arsenopyrite is an important gold-bearing sulfide mineral, and pretreatment is essential before gold extraction to maximize gold recovery. Bioleaching, with its advantages of simple operation and environmental friendliness, has received widespread attention over the past decade. However, the low efficiency and long cycle of bioleaching hinder its large-scale application. Humic acid (HA) is a potential substance that can enhance the bioleaching of arsenopyrite and has advantages such as ease of acquisition, and environmental friendliness. Currently, there is a lack of research on the promoting effect and mechanism of HA on the bioleaching of arsenopyrite under the action of mesophile microorganism. This study investigates the effects of HA mediated by Acidithiobacillus ferrooxidans on the arsenopyrite leaching behavior, the valence states and forms of arsenic. The results showed HA can promote the bioleaching of arsenopyrite and shorten the leaching cycle. The addition of 20 mg/L HA can significantly reduce the bioleaching cycle of arsenopyrite from 14 days (without HA) to 6 days. HA can promote the growth of microorganisms and enhance the Fe/S oxidation capacity of microorganisms. Meanwhile, HA can adsorb onto the mineral surface, facilitating the oxidation of arsenopyrite by Fe 3+ adsorbed by HA, thereby promoting the bioleaching of arsenopyrite. This study offers new insights into shortening arsenopyrite bioleaching cycle.