The Experimental Study Of Modified Fenton Chemical Oxidation Of Oil Contaminated Soils

Modified Fenton (MF) chemical oxidation does not need to change the pH value of soil, it can be repair oil contaminated soil in neutral condition and in situ, it is the most promising chemistry pre-oxidation technology. However, the MF chemical oxidation applies in different oil soil pollution intensity situation are rarely reports, especially the soil which the total petroleum hydrocarbon (TPH) concentration is more than 100 g/kg of heavy pollution almost hardly involved. This paper examines the MF oxidation of four different pollution intensity of petroleum contaminated soils and analyzes the oxidation of TPH and SOM; find the suitable scope of petroleum contaminated soil strength for MF chemical oxidation. And optimize the MF oxidation of oil contaminated soils, find the suitable MF chemical oxidation conditions of the subsequent bioremediation, this will provide the theory basis for repair of petroleum contaminated soil in the field. Test results shown as below:1. MF chemical oxidation of different concentration of oil contaminated soil(1) The oil concentration in polluted has important influence on modified Fenton chemical oxidation. The oil removal of low concentration contaminated soil is hgher than that of high concentration contaminated soil.(2) When the concentration of ferrous is 5.8mmol/L, and H2O2 concentration is 1100mmol/L, TPH removal efficiency of low concentration polluted soil (15g/kg 28g/kg) is 44.14% 45.77% while TPH removal efficiency of high concentration polluted soil (98g/kg ¹96g/kg) is only 5.35% 7.06%. The results indicated that is feasible for low polluted level to be oxidized by MF reagent.(3) Compare two addition methods of H2O2, the results indicated the TPH removal efficiency by graded MF is double of conventional addition mehod, and removal efficiency of SOM decreased to17%, it is a better addition of H₂O₂.2. Optimum of MF chemical oxidation of petroleum contaminated soils(1) The best molar rate of H₂O₂ / Fe is 1100/5.8, under this condition the TPH oxidation efficiency is 45.77% and SOM removal efficiency is 10.65%. When H₂O₂ concentration keep the same, the oxidation efficiency of TPH is twice times under 5.8 mmol/L of Fe2+ condition of 2.9 mmol/L. Optimal addition time of oxidant is 3 times, the TPH concentration from 26540mg/kg drop to 12812mg/kg, TPH oxidation rate reaches as high as 51.73%, SOM oxidation rate is low, only 6.62%. The amount of oxidant is fixed; SOM removal efficiency and TPH removal efficiency change trend is opposite, TPH are competitive relationship with SOM in soil.(2) Test found that the treatment effect in 8.5 pH value is superior to the pH of 3.5, TPH oxidation efficiency is increased to 10²0 percentage points, it proved that under the neutral pH condition, soil petroleum hydrocarbons was more easily oxidation by MF reagent.3.Combined process of MF chemical oxidation with bioremediation of oil contaminated soilAfter MF oxidation under optimal condition, bioremediation tests were carried out under inoculation and ono-vaccinated condition. The data shows that the TPH removal efficiency of two groups are 54.64% and 47.72%. MF reagent chemical oxidation will not reduce microbial activity in soil, but also can improve the subsequent bioremediation.