Simultaneous hypophosphite removal and phosphorus recovery by peroxymonosulfate coupled with core-shell structured...

Hypophosphite (P(I)) has been largely used in the industry, while it can contribute to eutrophication and pose significant public health risks. Conventional chemical precipitation processes struggle to remove and recover it due to the compound's high solubility. Iron-based advanced oxidation processes (AOPs) have gained attention for P(I) removal and recovery. This study developed a thin-layer Fe-Fe₂O₃ core-shell material to activate peroxymonosulfate (PMS) for highly efficient P(I) oxidation and simultaneous phosphorus recovery, which markedly accelerated the reaction kinetics. Specifically, 95.2 % P(I) removal was achieved within 20 min, with 87.3 % of the P(I) converted to P(V), accounting for the total phosphorus (TP) removal. Sulfate radicals (SO₄^•-) and hydroxyl radicals (^•OH) were the dominant reactive species, and ^•OH reacted approximately three times faster than SO₄^•- with P(I). Density functional theory (DFT) calculations elucidated the oxidation pathway of P(I), confirming the conversion from P(III) to P(V) as the rate-determining step. The system effectively suppressed Fe⁰ passivation and enhanced the Fe³⁺/Fe²⁺ redox cycle. Ultimately, the system demonstrates significant potential for simultaneous oxidation and recovery of P(I) from actual industrial wastewater, yielding FePO₄ and vivianite. This study provides a novel, efficient, and low-consumption strategy for the resource-oriented treatment of P(I)-laden industrial wastewater.