盐湖卤水萃取法提锂的工艺中，磷酸三丁酯-FeCl₃-煤油协萃体系在多次循环使用后萃取能力会下降甚至失效。将失效锂萃取剂中的Fe（Ⅲ）回收利用对盐湖提锂行业的持续发展具有重要意义。在高浓度盐酸体系中模拟失效锂萃取剂，以其中的Fe（Ⅲ）为铁源，NH₄H₂PO₄溶液为磷源，在非均相体系中制备电池级磷酸铁。研究了反应时间、氨水加入量、NH₄H₂PO₄溶液浓度、反应温度和搅拌速率对产品产率、粒径（D₅₀）和铁磷物质的量比的影响。结果表明，在优化的工艺条件下，可制得高纯度的单斜晶系二水磷酸铁，产率为89.43%、铁磷物质的量比为0.98、D₅₀为1.81 μm、比表面积为37.38 m²/g、含水量为19.64%，符合电池级磷酸铁的行业标准。以自制的磷酸铁为前驱体制备的LiFePO₄/C性能良好，在0.1C倍率下的首次放电比容量为146.58 mA·h/g，首次充放电效率为94.90%，恒流充放电循环80圈后的容量保持率为91.72%。研究表明，采用NH₄H₂PO₄溶液反萃沉淀法可有效回收失效锂萃取剂中的Fe（Ⅲ）并制备出电池级磷酸铁。

In the process of extracting lithium from salt lake brines by the extraction method，the extraction capacity of the tributylphosphate-FeCl₃-kerosene co⁃extraction system will decrease or fail after multiple cycles of use.The recovery of Fe（Ⅲ） in the spent extractant is of great significance to the sustainable development of recovery of lithium from salt lake brines.In this paper，a high concentration of hydrochloric acid system was used to simulate the spent lithium extractant.Fe（Ⅲ） in the spent lithium extractant was used as iron source and NH₄H₂PO₄ solution as phosphorus source to prepare iron phosphate in the heterogeneous system.The effects of reaction time，amount of ammonia，concentration of NH₄H₂PO₄ solution，reaction temperature and stirring speed on product yield，particle size（D₅₀） and Fe/P molar ratio were studied.The research showed that high⁃purity monoclinic iron phosphate dihydrate were obtained under optimized process conditions.The product′s yield was 89.43%，Fe/P molar ratio was 0.98，D₅₀ was 1.81 μm，the specific surface area was 37.38 m²/g，and the water content was 19.64%，which met the industry standard for battery⁃grade iron phosphate.The electrochemical performance of the LiFePO₄/C prepared from self⁃made iron phosphate as the precursor was excellent.The initial discharge specific capacity was 146.58 mA·h/g，the initial charge-discharge efficiency was 94.90%，and the capacity retention rate after 80 cycles of constant current charge and discharge was 91.72% at 0.1C.The research showed that the use of NH₄H₂PO₄ solution for reverse extraction and precipitation could effectively recover Fe（Ⅲ） from spent lithium extractants and prepare battery⁃grade iron phosphate.