Efficient recovery of high-purity 2D flaky R-FePO4 from lithium extraction slag leachate via solvent extraction and chemical precipitation

The recycling of spent lithium iron phosphate batteries (LFPs) has enormous market potential and great significance for environmental protection and sustainable development. Notably, lithium extraction slag (LES) recovery is a critical link in the full-process recycling of spent LFPs, while existing technologies are often limited by low impurity separation efficiency, poor environmental compatibility, or high costs. Herein, this study innovatively integrated solvent extraction with LES recovery and proposed a method for efficient impurity separation and preparation of high-purity 2D flaky regenerated iron phosphate (R-FePO 4 ). Three extractant systems were evaluated for purifying LES leachate, and TBP-kerosene was identified as the optimal extractant composition with corresponding optimal operating conditions determined. Fe and P could be co-extracted, and under conditions of 80% TBP volume fraction ( φ TBP  = 80%), 60 s extraction time, and initial phase ratio R  = 3, their single-stage extraction efficiencies reached approximately 99.20% and 38.50%, respectively, with excellent impurity separation performance. After cascaded extraction, the maximum extraction efficiencies of Fe and P reached 100% and 82.60%, respectively. McCabe-Thiele diagrams for Fe and P were constructed to determine the theoretical number of stripping stages. After three-stage countercurrent stripping, the maximum mass concentrations of Fe and P in the stripping solution reached 29.20 and 17.23 g L −1 , respectively, while contents of impurities (Al, Ni, Co, Mn, Cu, Ti) remained extremely low. HCl and R-FePO 4 were recovered from the stripping solution via evaporation and chemical precipitation, respectively. XRD, FT-IR, SEM, and EDS characterizations verified that the product was 2D flaky FePO 4 . Chemical titration and ICP-OES analysis showed the Fe/P molar ratio of R-FePO 4 was 0.969, and its impurity content met requirements of multiple standards simultaneously. Collectively, these results confirm the successful recovery of high-purity 2D flaky R-FePO 4 from LES via this method, with the comprehensive recovery rates of Fe and P reaching nearly 100%. Cyclic performance tests of the extractant demonstrate its excellent regenerative performance. The economic and environmental performance of the proposed process was evaluated, revealing its enormous industrial application potential. Eventually, a novel technical process is provided for the LES recycling industry to achieve maximum resource utilization.