The escalating world demand for strategic metals like Cu, Co, and Ni calls for efficient and environmentally friendly extraction methods to overcome traditional sulfide ore processing limitations. The conventional pyrometallurgical and acid-based hydrometallurgical routes are hampered by high energy requirements, environmental degradation, and poor metal yields due to passivation layers and undesired gangue reactions, or poor flotation recoveries to produce smeltable concentrates due to magnesium and iron constraints. This research examines alkaline glycine-based leaching as an alternative hydrometallurgical process to recover Cu, Co, and Ni from low-grade polymetallic sulfide ores (2.21% Ni, 0.18% Co, 0.45% Cu, P80 (80 should be a subscript)), which often contain platinum group metals as well. The research aimed to develop an integrated approach to recover these metals from low-grade concentrates. The primary operating parameters, such as glycine-to-Ni molar ratio, pH regulators, dissolved oxygen (DO) concentration, agitation speed, solids ratio, and temperature, were evaluated to determine the extraction of the metals. The results showed that when the glycine/Ni molar ratio was 6:1, double the stoichiometric requirement for the formation of the anionic tris-glycinato Ni (II) and Co(II) complexes, the extraction of Ni and Co was 82.3% and 82%, respectively. In contrast, the extraction of Cu was greater at lower glycine concentrations at the initial leaching stages. Dissolved oxygen (DO) concentration had a major influence on metal recovery, with the maximum extraction being 69.1% Ni, 65.3% Co, and 76.3% Cu at 25 mg/L DO. Optimization of 400 rpm stirring rates enhanced mass transfer and oxygen consumption by 30% from sub-optimal stirring rates. Cu and Co recovery by sodium sulfide precipitation was more than 99.9% Cu, and 98.9% Co. Nickel precipitation was not as effective because, presumably, back-oxidation of nickel sulfides in alkaline conditions occurred. This effect, coupled with the presence of Platinum Group Metals (PGMs), indicates that higher temperature and nitrogen purging would be necessary to improve Ni recovery. The implications of these observations identify the potential for glycine-based leaching to be used as a green, selective, and efficient process to treat refractory sulfide ores with higher recovery of metal content and enhanced sustainability compared to conventional extraction routes. • Alkaline glycine leaching enabled high base metal extraction, achieving 82.3% Ni, 82.0% Co, and 76.3% Cu. • Dissolved oxygen significantly enhanced metal recovery, increasing Ni extraction from 42.6% (no DO) to 69.1% (25 ppm DO). • Glycine leaching accommodated up to 30% solids content, maintaining high extraction efficiencies and reducing processing costs. • Copper recovery via sodium sulfide precipitation exceeded 99.9%, while Co recovery reached 98.9%, demonstrating effective downstream metal recovery.
Perea et al. (Sun,) studied this question.