Study On Fenton Oxidation Of Petroleum Hydrocarbons In Soil

Contaminated sites have received great attention because the contamination of these sites threatens the surrounding soil and underground water. Fenton oxidation methods have been successfully used to remove organic contaminants in soil, such as petroleum hydrocarbons / polycyclic aromatic hydrocarbons and so on. Although Fenton oxidation system has strong oxidation ability, but there are still many limiting factors when used alone. This paper regards desiel and PAHs of soil as the targeted pollutants. The experiments were carried out, as follow :(1) Fenton oxidation of diesel in neutral soil with lower content of iron;(2) biodegradation of diesel in Fenton oxidation pre-treated subsurface soil;(3) Fenton oxidation of PAHs in spiked soil and aged soil;(4) effect of surfactant Tween 80 on Fenton oxidation of PAHs in pre-oxidation soil. Results as following :(1) For the neutral soil with low iron content, apparent degradation of TPH(C10-C25) was not observed in the control treatment and Fenton-like treatment(3% H2O2). Apparent degradation of TPH(C10-C15) was observed in Fenton-like treatment(6% and 12% H2O2), while the degradation efficiency of TPH(C16-C25) was lower in Fenton-like treatment(6% and 12% H2O2). Chosing 6% H2O2 as Fenton regent, the more Fe2+ added, the higher degradation efficiency of TPH(C10-C25). Added 2%Fe2+ as catalyst, TPH(C10-C25) were degraded about 35%. Chosing 6% H2O2 and 1%Fe2 + as Fenton regent, the degradation efficiency of TPH(C10-C25) showed a rising trend with the decreasing pH value.(2) TPH(C10-C25) showed an obvious degradation in subsurface soil pre-treated with H2O2 after 5 days microbial incubation. After 30 days incubation, degradation efficiency of TPH in soil showed: unpreoxidied soil adding nutrients treatment > preoxidized soil adding nutrients treatment > preoxidized soil without adding nutrients treatment > unpreoxidized soil without adding nutrients treatment. In addition, this study found that low-carbon molecular weight contaminants in soil are relatively easily degradable, TPH(C10-C15) and TPH(C16-C20) were degraded up to 70%; while the degradation rate of TPH(C21-C25) was around 60%.(3) PAHs in spiked soil were easily degraded than PAHs in aged soil. Overall, the degradation efficiency of PAHs by three Fenton treatments showed: graded Fenton treatment > conventional Fenton treatment > Fenton-like treantment. The results of graded Fenton treatment(3 times oxidation) of PAHs in aged soil indicates that, after two times Fenton oxidation, the third time oxidation could not degrade the residual PAHs well, and it appeared "drag tail" phenomenon. The experiments that using Tween80 as surfacant to improve the degradation efficiency of PAHs in pre-oxidation(2 times) soil show that low dose Tween80 did not significantly enhance the Fenton oxidation degradation efficiency of PAHs in soil, while the high dose Tween80 can enhance the desorption and degradation of the 3, 4- rings PAHs of soil to a certain extent. However, high dose Tween80 can not enhance the desorption and degradation of the 5- rings PAHs of soil.