Electrokinetic in situ leaching of gold from intact ore

Electrokinetic in situ leaching (EK-ISL) is a novel in situ mining technology that uses an electric field to induce the migration of lixiviants through the subsurface to extract target commodities. Based on previous experiments with fine-grained unconsolidated material, this study assesses the feasibility of EK-ISL of gold from consolidated, unfractured, low-permeability ore material. Under the initially tested laboratory conditions, substantial ionic transport through low-permeability rock was achieved by applying a constant voltage. Subsequently, synthetic gold ore was positioned in between two rock sections and gold was successfully mobilised from the synthetic ore, transported through the second rock piece and collected in the target reservoir, albeit at a fairly slow rate. EK-ISL was then applied to two different gold ore samples. Both ores consumed considerable amounts of lixiviant before gold breakthrough occurred. Within the experimental timeframe, only a trace of gold was leached from Ore Sample 1. Nevertheless, over 50% of gold was recovered from Ore Sample 2 within a month after initial breakthrough. These experiments show that EK-ISL of gold from intact rocks is feasible, and also highlight the importance of characterising the reactivity of the host rock with respect to the selected lixiviant system prior to attempting EK-ISL. It was also found that during EK-ISL the hydraulic permeability of the ore was increased as a result of the dissolution of gangue minerals, which enhanced electro-migration of ions over the investigation timeframe.