Enhanced oxidative bioleaching for nickel and metal recovery from arsenic ores moves toward efficient and sustainable extraction

The research focuses on extracting nickel and other valuable elements through oxidative bioleaching from two distinct arsenic-rich ores of varying grades. This process involved utilizing a mix of mesophilic and moderately thermophilic bacteria in shake flasks with different pulp density levels to bio-leach nickeline. Mesophilic bacteria achieved over 99% nickel dissolution from both low- and high-grade ores within 10 and 28 days, respectively, at pulp densities of 0.5% and 1%. In contrast, abiotic control and chemical tests showed significantly lower nickel dissolution rates (approximately 6.9% and 26.1% for low-grade; 10.3% and 45% for high-grade samples). Moderately thermophilic bacteria achieved complete nickel dissolution from the low-grade ore at a 0.5% pulp density, while dissolution from the high-grade ore reached approximately 63%. In comparison, abiotic controls and chemical achieved only 19% and 39% dissolution for the high-grade ore, and 21.9% and 45% for the low-grade ore, respectively. X-ray diffraction (XRD) analysis confirmed the formation of scorodite as a secondary phase due to arsenic solubilization from primary minerals in the presence of iron. Kinetic modelling revealed that the bioleaching of the low-grade ore was predominantly controlled by a mixed reaction mechanism, whereas chemical factors limited the bioleaching rate of the high-grade ore. This research underscores the efficacy of oxidative bioleaching using mixed bacterial cultures and highlights its potential for efficiently extracting nickel and other valuable metals (cobalt and copper) from arsenic-bearing ores under controlled pulp density conditions.