Study on process of recovery of Fe(Ⅲ)from spent lithium extractant and preparation of battery grade iron phosphate
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 solu-tion,reaction temperature and stirring speed on product yield,particle size(D50)and Fe/P molar ratio were studied.The re-search 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 perfor-mance of the LiFePO4/C prepared from self-made iron phosphate as the precursor was excellent.The initial discharge spe-cific 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 solu-tion for reverse extraction and precipitation could effectively recover Fe(Ⅲ)from spent lithium extractants and prepare bat-tery-grade iron phosphate.
lithium extractantiron phosphatelithium iron phosphate
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