Process and application study on the preparation of battery-grade FePO4 by high-temperature activated leaching-precipitation of iron phosphate slag
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(FePO4)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 FePO4 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 FePO4 were also investigated.The concentrations of Fe and P elements in the leaching solution and the crystal structure,morphology and particle size of FePO4 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(FePO4)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(LiFePO4)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 FePO4 fully met the requirements of the precursor of LiFePO4 cathode material.
iron phosphate slagactivationleachprecipitation methodbattery-grade iron phosphate
国家科技期刊平台
NSTL
万方数据
