Facilitation of pyrite dissolution through enhanced electron transfer in pyrite-fuel cells

This study investigates a pyrite-fuel cell (PFC) approach to overcome challenges in pyrite oxidation for metal recovery and environmental mitigation, particularly under acidic conditions that inhibit Fe²⁺ oxidation and cause electron passivation. By introducing an external circuit, the PFC allows efficient electron transfer. This study compares three oxidation pathways: direct oxidation by dissolved oxygen, bio-mediated oxidation by Acidithiobacillus ferrooxidans, and electrochemical oxidation. Using 2.5 g of pyrite in 125 mL of pH 2 electrolyte, the PFC showed significantly higher Fe leaching (0.84 mM) over four weeks compared to 0.11 mM and 0.56 mM for dissolved oxygen and A. ferrooxidans, respectively. Importantly, Fe-O layer formation did not result in electron passivation within the electrochemical system, as verified by microscopy techniques. Enhanced electron transfer, facilitated by lower external resistance, accelerated pyrite dissolution, while a redox potential exceeding 0.66 V further boosted dissolution rates. This study highlights PFCs as a sustainable and efficient method for improving pyrite oxidation and metal recovery, offering clear advantages over conventional oxidation techniques.