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

酸浸是湿法冶金中必不可少的单元，但它既耗时又需要浓酸。使用亚临界水萃取 (SWE) 和微波辅助从废镍金属氢化物 (NiMH) 电池中浸出贵重和稀土元素 (REE)，例如 Ni、Co、La、Nd 和 Ce 的过程强化提取（MAE）。SWE 的结果表明，HCl 的性能优于 H ₂ SO ₄和 HNO ₃. 浸出效率随着反应温度从 100°C 增加到 150°C 而增加，并且随着 HCl 浓度的增加而增加。SWE 使用 0.5 N HCl、20 g/L 固体浓度、9.8 bar 初始压力、100°C 5 分钟非常有效，Ni 的浸出效率为 99.85%，Co 的浸出效率为 91.72%，La 的浸取效率为 96.26%，85.75 Nd 为 %，Ce 为 84.37%，总能耗为 2,640 kJ。当加热速率从 30°C/min 增加到 70°C/min 时，使用 0.5 N HCl 的 MAE 浸出效率略有下降，而随着反应时间从 5 增加到 30 分钟，它的浸出效率增加。与 SWE 和常规浸出相比，MAE 是最节能的，总共需要 874.1 kJ 才能达到 Ni 的 85.93%、Co 的 77.60%、La 的 64.04%、Nd 的 75.01% 和 Ce 的 57.17%，分别在 1 N HCl 的实验条件下，固体浓度为 20 g/L，100°C 5 分钟。新型酸浸法显示出从电子垃圾中回收金属的潜力。