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    废磷酸铁锂全组分资源化及杂质定向控制

    Total component recycling and impurity directional control of waste lithium iron phosphate

    • 摘要: 为了实现废磷酸铁锂的全组分资源化,采用HCl、H2O2溶液作为浸取剂,LiOH·H2O作为除杂剂,系统地研究废磷酸铁锂提锂过程中铁、磷、锂、铝、铜、镁元素的迁移规律。通过调控系统pH值实现对铝、铜、镁杂质元素的定向控制,得到较高纯度的FePO4·xH2O渣和氯化锂精制溶液。实验结果表明:H2O2及HCl试剂浓度分别为0.7和1.0 mol·L-1、搅拌转速n为300 r·min-1时,锂元素浸出率接近100%,但浸出液中铁、磷杂质的质量浓度ρB分别达到18.3、11.2 g·L-1;采用LiOH·H2O将系统pH调控至1.1±0.05,可使质量分数为97.7%以上的铁、磷以FePO4·xH2O形式沉淀,其他元素保留在浸出液中;将浸出液pH值调至7.0~8.0即可将铝、铜元素排出系统;再将溶液pH值调至11.0~11.5,可将镁元素以Mg(OH)2的形式去除,最后采用盐酸将pH值调回中性,即可得到氯化锂精制溶液,锂的回收率为97.3%。

       

      Abstract: In order to realize the full component recycling of waste LiFePO4, the migration law of iron, phosphorus, lithium, aluminum, copper and magnesium in lithium extraction from waste LiFePO4 was systematically studied using HCl and H2O2 as leaching agents and LiOH·H2O as an impurity removal agent. Directional control of Al, Cu and Mg impurities was realized by adjusting system pH values, and high purity FePO4·xH2O slag and lithium chloride refining solution were obtained. The experimental results show that when the concentrations of H2O2 and HCl are 0.7 and 1.0 mol·L-1 respectively, and the stirring speed n is 300 r·min-1 lithium leaching rate is close to 100% while the contents of iron and phosphorus impurities in the leaching solution are 18.3 and 11.2 g·L-1, respectively. More than 97.7% of iron and phosphorus precipitated as FePO4·xH2O when using LiOH·H2O to adjust the system pH to 1.1±0.05, and other elements remained in the leaching solution. Aluminum and copper can be discharged from the system by adjusting the pH value of the leaching solution to 7.0-8.0. When the pH value of the solution was adjusted to 11.0-11.5, magnesium can be removed in the form of Mg(OH)2. Finally, the pH value was adjusted back to neutral with hydrochloric acid to obtain a refined solution of lithium chloride with lithium recovery of 97.3%.

       

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