Manipulating electrochemical phosphate recovery from acidic wastewater for synthesizing LiFePO₄/C cathode material

Phosphorus (P) recovery from wastewater offers a sustainable solution for mitigating pollution and securing resources for applications like lithium-ion batteries, where ferric phosphate is a valuable precursor. This study evaluates iron electrolysis for P removal and recovery from acidic wastewater with high phosphate concentrations and medium Ca²⁺ levels. The results suggested that effective P removal and high-purity iron phosphate production can be achieved by varying initial pH, current density, and oxidation conditions. Importantly, slow Fe release rates (0.02-0.04 mmol L⁻¹ min⁻¹) favored ferric phosphate formation (71%-77% removal), while faster rates (0.16-0.46 mmol L⁻¹ min⁻¹) predominantly produced vivianite (∼ 65% removal). In addition, air flush can enhance dissolved oxygen flux, achieving 89% P removal under rapid Fe release but with mixed products. H₂O₂ addition improved in situ Fe(II) oxidation, achieving 92% P removal and purer ferric phosphate. Compared to chemical precipitation, which required pH adjustment and suffered from Ca co-precipitation, iron electrolysis produced purer ferric phosphate directly, without pH pre-adjustment. The recovered ferric phosphate showed excellent potential as a precursor for high-performance LiFePO₄/C cathode material. These findings position iron electrolysis as a promising approach for sustainable P recovery and resource valorization from wastewater.