Remediation of PAHs-contaminated soil by coupling Triton X-100 assisted washing and BiOBr/g-C3N4 photocatalytic process: Insights to the degradation mechanism and soil washing recycling

A remediation strategy for polycyclic aromatic hydrocarbons (PAHs) in soil was proposed that combined soil washing (SW) and photocatalytic oxidation. In this study, naphthalene (2-ring Nap), phenanthrene (3-ring PHE), and pyrene (4-ring Pyr) served as model pollutants. We assessed the efficacy of Triton X-100 (TX-100) in desorbing PAHs from contaminated soil and its impact on subsequent photocatalytic degradation. TX-100 achieved desorption efficiencies of 72.1% for Nap, 63.3% for PHE, and 52.1% for Pyr during SW. The desorption process of PAHs from soil showed strong closely dependent on TX-100 concentration. Furthermore, a BiOBr/g-C 3 N 4 -30% (BOB/CN-30%) photocatalyst was employed to decompose PAHs in both synthetic and real SW effluents. Quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed the generation of active species (h + , OH, and O 2 − ) in the BOB/CN-30% system. Based on the photocatalytic treatment of PAHs in the synthetic SW effluent, the reactivity impact of TX-100 on PAH degradation by BOB/CN-30% depended on the TX-100 concentration. Optimal TX-100 levels enhanced PAH solubilization and decomposition, whereas excessive concentrations formed dense micelles that obstructed PAH degradation. Moreover, the coupled system exhibited efficient recirculation in real SW tests, underscoring its potential as a remediation option for PAHs-contaminated soils.