Overcoming the Challenges of Gold-Arsenic Co-occurrence in Mineral Processing

As easily processable gold ore resources gradually become depleted, arsenic-bearing gold ores that are difficult to process have become a key resource in gold mining. Gold and arsenic often occur in close association, with arsenic minerals encapsulating fine gold particles; this not only lowers the effective grade of the ore but also significantly interferes with the leaching process, resulting in a continuous decline in gold recovery rates.

I. Arsenic-Suppressing Gold Flotation Process

Flotation is the fundamental preliminary process for separating gold and arsenic-bearing minerals, with the core of the entire process lying in the formulation of the reagent system. By using selective inhibitors to suppress the flotation of arsenic sulphides, combined with specialised collectors to enrich gold-bearing minerals, effective separation of gold and arsenic-bearing minerals is achieved. Following separation, the gold-bearing product is directed to the subsequent leaching stage, whilst the arsenic-bearing minerals are discharged as tailings. This minimises the interference of arsenic in the gold extraction process at source and is suitable for ore with moderate arsenic content and good mineral liberation.

II. Oxidative Roasting Combined with Cyanide Leaching Process

This process is predominantly used for gold ores with high arsenic content and severe sulphide encapsulation. Roasting is carried out in an atmospheric or oxygen-enriched high-temperature environment to thoroughly decompose arsenic-bearing sulphides such as arsenopyrite and pyrite, breaking down the mineral structure and releasing the internally encapsulated gold particles. Following pre-treatment to remove arsenic and sulphur, cyanide leaching is carried out, resulting in a significant improvement in gold leaching efficiency. This process is mature and stable, making it suitable for large-scale mining operations.

III. Bacterial Oxidation Pre-treatment – Cyanide Process

Bacterial oxidation is a mild and environmentally friendly method for arsenic removal, relying on specialised acidophilic microorganisms to decompose arsenic-bearing sulphide minerals. During the microbial metabolic process, sulphur and arsenic components are stripped from the ore, fully exposing the encapsulated gold and reducing the consumption of cyanide reagents in subsequent stages. The entire process operates at ambient temperature and pressure, with low energy consumption and minimal pollutant emissions, making it particularly suitable for small and medium-sized mines and mining areas subject to strict environmental regulations. The only drawback is that the oxidation reaction cycle is relatively longer.

IV. Green, Cyanide-Free Leaching Process

As traditional cyanide reagents pose environmental risks, non-cyanide leaching represents a new, clean solution for gold extraction. By utilising non-toxic leaching agents such as thiosulphates and thiocyanates, gold is leached directly following arsenic removal pre-treatment. The entire process generates no highly toxic cyanide-containing wastewater or tailings, thereby complying with green mining standards and making it suitable for projects subject to stringent environmental requirements or located near residential areas or water protection zones.