MIL-88A(Fe) Adsorption-Photocatalytic Synergistic Degradation of Phenanthrene-Pyrene Composite Pollutants in Soil
Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants ubiquitously present in soils, posing severe risks to ecosystems and human health. This study synthesized MIL-88A(Fe) via a hydrothermal solvent method and applied it to the photocatalytic degradation of phenanthrene-pyrene (PHE-PYR) composite contaminants in soil, investigating the adsorption-photocatalytic synergy. Results demonstrated that adsorption of PHE-PYR onto MIL-88A(Fe) was dominated by physical and monolayer surface adsorption, with a maximum adsorption capacity of 97.25 mg/kg. This strong adsorption increased pollutant concentration near active sites, accelerating photocatalytic degradation. Under optimal conditions—3% catalyst dosage, 40% soil water content, 60 min visible light irradiation, initial pollutant concentration of 200 mg/kg, and acidic soil—the total degradation efficiency reached 79.20%. Photoelectrochemical characterization revealed significant visible-light response (200–600 nm), a narrow bandgap of 3.04 eV, and favorable band structure facilitating efficient electron-hole separation. Quenching experiments identified superoxide radicals (·O2−) and holes (h+) as primary reactive species. GC-MS analysis of intermediates indicated that PYR undergoes hydroxylation, oxidation, and ring-opening to form PHE, which is further hydroxylated and oxidized, ultimately mineralizing to CO2 and H2O. This work provides an efficient strategy for remediating PAH-contaminated soils.