Heterogeneous photo-fenton system using Fe3O4@tourmaline for rapid and pH-tolerant mineralization of refractory organophosphorus pollutants: piezoelectric synergy with UV-driven iron cycling

Background The persistence and eutrophication risks posed by organophosphorus pollutants and P recovery have attracted great concern. To overcome the narrow pH window and poor Fe 2+ /Fe 3+ cycling of conventional Fenton processes for the decontamination of organophosphorus effluents, a novel heterogeneous fenton process is required. Methods Herein, a Fe 3 O 4 -modified tourmaline composite (Fe 3 O 4 @Tol) was prepared via hydrothermal reaction and a heterogeneous photo-Fenton system was established with UV assistance. Significant Findings The composite achieved 89.97% conversion rate of 1-hydroxyethylidene-1,1-diphosphonic acid(HEDP) within 10 min with >80% TOC removal under neutral conditions (pH=7). Density-functional theory calculations and mechanistic investigations revealed that the piezoelectric effect of tourmaline promotes H₂O₂ dissociation and electron transfer, while UV irradiation accelerates Fe³⁺/Fe²⁺ cycling and H₂O₂ decomposition. These synergistic effects elevated H₂O₂ utilization efficiency to 81.18%. The system rapidly degraded other organophosphorus compounds (phytic acid, nitrilotrimethylene triphosphonic acid) and tolerated common inorganic salts, maintaining conversion rates above 70%. Fe 3 O 4 @Tol retained 72.21% of its initial activity after five cycles. This pH-tolerant, recyclable, and highly efficient technology offers a promising solution for the removal of recalcitrant organophosphorus pollutants from industrial wastewater.