Feasibility of electrokinetic in situ leaching of gold

Conventional gold mining operations are facing significant challenges due to declining ore grades and increasingly higher strip ratios. To meet global demands while limiting associated environmental impacts, alternative techniques to extract resources, including gold, are urgently needed. We suggest that in situ leaching coupled with electrokinetics (EK-ISL) could potentially enable recovery of gold from (subeconomic) ores with a significantly smaller environmental footprint than current mining techniques. EK-ISL would involve the leaching of gold, in situ, using a lixiviant that is introduced via a set of wells. A voltage gradient is applied to transport the lixiviant through the orebody. The gold is leached and also transported towards a set of recovery wells. At the surface the gold is recovered and the lixiviant can be recycled. This study was designed to verify the in-principle feasibility of this novel technique. A series of laboratory experiments was performed with an iodide/tri-iodide solution as lixiviant to extract gold from unconsolidated porous media. Experiments in which pyrite was included as proxy gangue mineral and complimentary bottle roll tests showed a declining efficiency of EK-ISL gold leaching with increasing pyrite oxidation. However, 80% gold recovery was still achieved, even with the highest tested pyrite concentration (5.26 wt%). The coupled transport and reaction processes were interpreted and quantified through numerical model simulations that were constrained by the experimental observations. Overall the experimental and numerical modeling results suggest the in-principle feasibility of EK-ISL.