磷铁渣高温活化浸出-沉淀法制备电池级FePO_(4)的工艺及应用

Process and application study on the preparation of battery-grade FePO_(4)by high-temperature activated leaching-precipitation of iron phosphate slag

磷铁渣是黄磷生产的副产物之一,化学性质稳定,常作为固体废物处理,不仅污染环境,也消耗了大量人力物力。如何合理利用磷铁渣中铁(Fe)、磷(P)元素是磷化工企业必须解决的问题。以磷铁渣制备磷酸铁(FePO_(4))的传统技术存在能耗大、副产物安全隐患大、难以实现工业化生产等缺点。有鉴于此,本文采用磷铁渣、磷酸、盐酸、氨水为原料,通过高温活化浸出-沉淀法制备了电池级FePO_(4)。在高温活化浸出阶段,探究了浸出时间、浸出温度、盐酸浓度、液固比与磷铁渣浸出率的关联规律。并研究了反应温度、时间、pH、投料比等条件对制备FePO_(4)性能的影响。对浸出液中Fe、P元素浓度和FePO_(4)晶体结构、形貌和粒度进行了分析。实验结果表明,磷铁渣浸出的最佳条件是:浸出时间3h、浸出温度90℃、盐酸浓度5.5mol/L、液固比20mL/g,在此浸出条件下Fe元素浸出率可达93.55%,P元素浸出率可达82.21%,固体渣浸出率可达90.06%。沉淀反应过程的最佳条件为:反应温度70℃、反应时间2h、反应pH=1.2、Fe/P投料比为1,此条件制备的磷酸铁(FePO_(4))材料结晶度高,形貌均匀,分散性好,一次粒径为100~200nm,铁磷比为0.97,杂质含量完全符合行业标准。以此合成的磷酸铁锂(LiFePO_(4))正极材料电化学性能较好,在1C倍率下,放电比容量可达到151.62mA·h/g,表明所制备的FePO_(4)完全满足LiFePO_(4)正极材料前体的要求。

Phosphorus iron slag is one of the by-products of the production of yellow phosphorus.It is often treated as solid waste due to its chemically stable,which not only pollutes the environment but also consumes a lot of manpower and material resources.How to rationally utilize the iron(Fe)and phosphorus(P)elements in iron phosphate slag is a problem that must be solved by phosphorus chemical enterprises.The traditional technology of preparing iron phosphate(FePO_(4))from iron phosphate slag has the disadvantages of high energy consumption,large safety hazards of by-products and difficulty in industrialized production.Thus,this paper adopted iron phosphate slag,phosphoric acid,hydrochloric acid and ammonia as raw materials,and prepared battery-grade FePO_(4)by a combination of high-temperature activated leaching-precipitation method.In the stage of high-temperature activated leaching,the correlation law between the leaching time,the leaching temperature,the concentration of hydrochloric acid,the liquid-solid ratio and the leaching ratio of iron phosphate slag was explored.The effects of reaction temperature,time,pH and feeding ratio on the performance of prepared FePO_(4)were also investigated.The concentrations of Fe and P elements in the leaching solution and the crystal structure,morphology and particle size of FePO_(4)were analyzed.The experimental results showed that the optimal conditions for the leaching of ferrophosphorus slag were:leaching time of 3h,leaching temperature of 90℃,hydrochloric acid concentration of 5.5mol/L and liquid-solid ratio of 20mL/g,under which the leaching rate of elemental Fe could be up to 93.55%,the rate of elemental P could be up to 82.21%,and the rate of solid slag leaching could be up to 90.06%.The optimal conditions of the precipitation reaction process were:reaction temperature 70℃,reaction time 2h,reaction pH=1.2 and Fe/P feeding ratio of 1.This condition of the preparation of iron phosphate(FePO_(4))materials with high crystallinity,uniform morphology,good dispersion,a particle size of 100—200nm,iron and phosphorus ratio of 0.97 and the content of impurities was in full compliance with the industry standards.The lithium iron phosphate(LiFePO_(4))cathode material synthesized in this way had good electrochemical performance,and the discharge specific capacity can reach 151.62mA·h/g at 1C multiplicity,indicating that the prepared FePO_(4)fully met the requirements of the precursor of LiFePO_(4)cathode material.