Dual-functional recycling of LiFePO4: Lithium extraction and Fe-P photocatalyst wastewater treatment

The recycling of lithium iron phosphate (LiFePO₄, LFP) cathode-materials has garnered significant attention due to its considerable social and economic benefits. While most-research has focused on the efficient recovery of lithium, the sustainable management of residual iron-phosphorus components remains a relatively understudied challenge. To address this gap, this study proposes an air-calcination-assisted method for the selective leaching of Li from spent lithium iron phosphate cathode powder (s-LFP), along with the subsequent utilization of the resulting iron-phosphorus solid (r-FP) for the photocatalytic degradation of tetracycline hydrochloride (TC). Notably, atmospheric oxygen during calcination facilitates the oxidation of Fe(II) in LiFePO₄ to Fe(III), thereby effectively suppressing Fe leaching during the subsequent acid treatment and achieving a high lithium leaching efficiency of 98.15 %. Remarkably, the r-FP exhibits photocatalytic capability to degrade 76 % of TC within 60 min, outperforming commercial FePO₄. Combined experimental and theoretical calculations reveal that r-FP acts as an effective photocatalysts for TC-degradation, with superior performance attributed to enhanced carrier mobility. Furthermore, r-FP maintains its photocatalytic activity primarily through increased production of h⁺ and •O₂^-. This integrated strategy offers new insights into the sustainable recycling of Li, Fe, and P from end-of-life LFP.