Efficiency and mechanism on photocatalytic degradation of fluoranthene in soil by Z-scheme g-C3N4/α-Fe2O3 photocatalyst under simulated sunlight

Polycyclic aromatic hydrocarbons (PAHs) in soil have potential harm on human health. However, remediation of PAH-contaminated soils through photocatalytic technology remains a challenge. Therefore, the photocatalyst g-C3N4/alpha-Fe2O3 was synthesized and applied to photocatalytic degradation of fluoranthene in soil. The physicochemical properties of g-C3N4/alpha-Fe2O3 and various degradation parameters, such as catalyst dosage, the ratio of water/soil, and initial pH, were investigated in detail. In soil slurry reaction system (water/soil=10:1, w/w), the optimal degradation efficiency on fluoranthene was 88.7% after simulated sunlight irradiation for 12 h (contaminated soil=2 g, initial fluoranthene concentration=36 mg/kg, catalyst dosage=5%, and pH=6.8), and the photocatalytic degradation followed pseudo-first-order kinetics. The degradation efficiency of g-C3N4/alpha-Fe2O3 was higher compared with P25. Degradation mechanism analysis showed that center dot O-2(-) and h(+) are the main active species in photocatalytic degradation process of fluoranthene by g-C3N4/alpha-Fe2O3. Coupling g-C3N4 and alpha-Fe2O3 enhances the interfacial charge transport capacity via Z-scheme charge transfer route and inhibits the recombination of photogenerated electrons and holes of g-C3N4 and alpha-Fe2O3, then significantly improves the production of active species and photocatalytic activity. Results showed that photocatalytic treatment of soil by g-C3N4/alpha-Fe2O3 is an effective strategy for remediation of soils contaminated by PAHs.