Polycyclic aromatic hydrocarbons (PAHs) entering into soils via sewage sludge could be posing arresting environmental risks. Photocatalytic remediation has been considered as a powerful tool of degrading PAHs in soils. In the present study, a synthesized nanometer mixed-crystal TiO₂ was employed to investigate its effects on PAHs degradation in soils by Ultra Violet (UV).Two typical substances of PAHs widely detected in sewage sludge (phenanthrene and pyrene), were added into soils from farmland to provide polluted soil for a series of simulated experiments. These polluted soil samples were mixed with five different levels of the synthesized TiO₂ (0, 1%, 2%, 3%, and 4%, wet weights) and the decreases of PAHs under different conditions were compared. The results showed that among the five treatments, the activities of the synthesized photocatalysts followed the order of 0<1%<2%<4%<3%, and the 3% of TiO₂ addition was determined as the optimum condition. Moreover, it was found that the degradation of PAHs could increase with the increasements of H₂O₂, photon flux, and humic substances in treated soils. Our findings supports the perspective of using nanometer synthesized mixed-crystal TiO₂ in the degradation of PAHs in contaminated soils by sewage sludge addition and provides hints on understanding the mechanism of developing photocatalytic remediation in PAHs-contaminated soils.

Photosensitized degradation of phenanthrene and pyrene using humic acid (HA) was applied for remediation of PAHs. The desired dosages of HA (0, 10, 20, 30, and 40 mg kg⁻¹) were added into the PAHs contaminated soil, and soil samples were randomly located in photodegradation chamber under the UV lamps for 25 h. The results suggested that the photosensitized degradation of phenanthrene and pyrene obeyed the pseudo-first-order kinetics. Moreover, the increased concentration of O₂, H₂O₂ and light intensity enhanced the fast degradation of phenanthrene and pyrene. All the results disclosed that HA-assisted photosensitized degradation of PAHs was an available choice for remediation of PAHs polluted soil in the practice.