Process intensification for valuable metals leaching from spent NiMH batteries

Acid leaching is an essential unit in hydrometallurgy, yet it time consuming and requires concentrated acids. Process intensification examined for the of valuable rare earth elements (REEs), such as Ni, Co, La, Nd, Ce, from spent nickel metal hydride (NiMH) batteries using subcritical water extraction (SWE) microwave-assisted (MAE). Results SWE revealed that HCl performed better than H2SO4 HNO3. Leaching efficiency increased reaction temperature 100 to 150°C, with concentration. was very effective 0.5 N HCl, solid concentration 20 g/L, initial pressure 9.8 bar, 100°C 5 min, 99.85% 91.72% 96.26% 85.75% 84.37% Ce found, total energy consumption 2,640 kJ. MAE decreased slightly when heating rate 30 70°C/min, min. Compared conventional leaching, most energy-efficient, 874.1 kJ required reach 85.93% 77.60% 64.04% 75.01% 57.17% respectively under experimental conditions 1 Novel acid methods showed promising potential metals recovery e-waste.