Abstract:
This study investigates the effectiveness of Acidithiobacillus ferrooxidans in enhancing gold
recovery from refractory ores at the Tira Gold Mine in Busia, Uganda. Conventional extraction
methods, such as cyanidation and mercury amalgamation, rely on hazardous chemicals, posing
environmental risks and yielding low recovery rates for sulfide-bound gold. As a sustainable
alternative, bioleaching with A. ferrooxidans was explored to dissolve sulfides and liberate
encapsulated gold without toxic reagents.
Laboratory experiments on bioleaching at conditions (pH 2.0–3.0, 25–30°C, 5% pulp density)
using ore samples characterized by XRF (42.5% SiO₂, 28.8% Fe₂O₃) and AAS (45.83 g/t
Au). A. ferrooxidans was successfully isolated from local tailings, with growth confirmed via
Gram staining and OD600 monitoring. Over 12 days, bioleaching achieved 54.64% gold
recovery, significantly outperforming the control (0.31% recovery). Validation of the
microbial role in gold dissolution is supported by pH decline (2.45 → 2.31) and the relatively
stable mesophilic temperatures.
The results demonstrate A. ferrooxidans as a viable, eco-friendly alternative for refractory ore
processing, aligning with Sustainable Development Goals (SDGs) by reducing chemical
reliance. Future work should scale trials to heap leaching and assess trace element impacts.
This study contributes to advancing green mining technologies in artisanal and small-scale gold
mining (ASGM) sectors.
