废旧磷酸铁锂正极材料的硫酸熟化-水浸工艺研究

为提高磷酸铁锂中Fe、Li和P浸出率,同时实现高效去除Cu、Al和F,开发了硫酸熟化-水浸、铁粉置换除铜、化学沉淀-萃取二段除铝工艺。结果表明,在熟化时间2.5 h、熟化温度110 ℃、固液比4.0/1、水浸温度60 ℃及水浸时间2 h的最佳条件下,硫酸熟化-水浸工艺可将浓硫酸的使用量降至理论值的0.75倍,此时铁浸出率达95%以上,氟脱除率达74.4%; 铁粉置换除铜过程中,控制初始pH=1.2,铁粉加入量为理论值的1.2倍时,浸出液中残留的Cu²⁺浓度可降至4.9 mg/L以下; 采用化学沉淀-P204萃取二段除铝工艺,可将浸出液中Al³⁺浓度降至10 mg/L以下。

A Combined Process of Sulfuric Acid Curing and Water Leaching for Spent LiFePo4 Cathode Material

In order to improve the leaching rate of Fe, Li and P in LiFePO₄ and realize the efficient removal of Cu, Al and F at the same time, a processing technique was developed, consisting of sulfuric acid curing and water leaching, iron powder replacement for copper removal, plus a two-stage aluminum removal by chemical precipitation and extraction. The results show that under the optimal experimental conditions, including the curing time of 2.5 h, curing temperature of 110 ℃, a solid-liquid ratio of 4.0/1, water leaching temperature of 60 ℃ and water leaching time of 2 h, the sulfuric acid curing and water leaching process can bring the amount of concentrated sulfuric acid reduced to 0.75 times the theoretical value, and also result in the Fe leaching rate over 95%, and the fluorine removal rate at 74.4%. In the process of iron powder replacement for copper removal, the concentration of residual Cu²⁺ in the leaching solution can be reduced to less than 4.9 mg/L by controlling an initial pH at 1.2 and the addition of iron powder at an amount of 1.2 times the theoretical value. Then, the concentration of Al³⁺ in the leaching solution can be reduced to less than 10 mg/L by adopting a two-stage aluminum removal process consisting of chemical precipitation and extraction by P204.