Selective phosphate recovery from acidic phosphogypsum leachate via Fe(III) precipitation for lithium iron phosphate precursor production.

Industrial phosphogypsum leachate represents an underutilized secondary phosphorus resource but remains difficult to valorize due to its extremely acidic conditions and complex impurity composition. This study reports and demonstrates a selective and pretreatment-free strategy for phosphate recovery from real phosphogypsum leachate via Fe(III)-induced precipitation, enabling the production of high-value iron phosphate as a potential precursor for lithium iron phosphate (LiFePO4) batteries. Under optimized conditions, phosphate removal reached 98.1 % while co-precipitation of competing cations remained minimal, resulting in an iron phosphate purity of 93.5 % in the calcined recovered product. Mechanistic investigation revealed that phosphate removal was governed not only by FePO4 precipitation but also by additional adsorption onto amorphous iron phosphate, which contributed to removal beyond stoichiometric predictions. Fluoride was found to partially compete for adsorption sites but did not significantly affect phosphate removal at sufficient Fe dosing. Calcination effectively eliminated fluorine impurities, enabling the recovered product to meet battery precursor specifications. The LiFePO4/C cathode synthesized from the recovered material exhibited an initial specific discharge capacity of 42 mAh/g at 100 mA/g and maintained 99 % capacity after 100 cycles, demonstrating stable electrochemical performance. TEA showed a positive Net Present Value with a payback period of approximately 6 years, suggesting economic feasibility of phosphate recovery. This work provides practical technical and economic data for implementing Fe(III)-based phosphate recovery from phosphogypsum leachate, and demonstrates a technically feasible pathway for upgrading wastewater phosphorus to battery precursors in industrial practice.