H₂O₂/Na₂S₂O₈ Double Oxidation System For Treatment Of Soil Contaminated By Petrolcum Hydrocarbon

The single hydrogen peroxide oxidation system and single sodium persulfate oxidation system are attracting much attention due to their strong oxidation capacity for the effective degradation of organic pollutants.However,they have restrictions in the application.Therefore,it is of great significance to study the treatment technology of hydrogen peroxide/sodium persulfate oxidation system for treating soil petroleum hydrocarbon pollution.In this paper,the activation of H₂O₂,Na2S2O8 and H₂O₂/Na2S2O8 by Fe2+ was investigated for degradation of petroleum hydrocarbons.The research mainly investigated the oxidation capacity of single and combined systems,the oxidation mechanism of the three oxidation systems,and the influence of TPH degradation by pH,temperature,oxidant dosage and activator dosage in the combined oxidation system.The specific research results are as follows:（1）The results show that the Fe2+/H₂O₂/Na2S2O8 oxidation system exhibited significantly higher oxidation capacity toward petroleum hydrocarbons degradation than the systems with a single oxidant.Moreover,the activator dosage was an important affecting factor of the three systems.Adding Fe2+,the oxidation capacity of the three oxidation systems were significantly improved.But,Fe2+ dosage was excessive,the oxidation effect of the oxidative system became worse.Therefore,the optimal molar ratio of oxidant to activator is 1:1.The degradation rate of petroleum hydrocarbons significantly improve with the increase of oxidant dosage.While oxidant dosage increasing from 0.05 mol/L to 0.5 mol/L,the degradation rates of the three oxidation systems for petroleum hydrocarbons degradation are increased by 50%,40%,and 47%,respectively.So the best oxidant dosage was 0.5mol/L.（2）The results of the study showed that the degradation process of the H₂O₂ oxidation system was mainly concentrated in the first hour of the reaction.The degradation process of Fe2+/Na2S2O8 system and Fe2+/H₂O₂/Na2S2O8 system can be divided into the rapid degradation stage in the early stage and the slow degradation stage in the later stage.The OH·played a major role in the Fe2+/H₂O₂ oxidation system,in the Fe2+/Na2S2O8 system,it existed OH·and SO4-·,SO4-· was the main free radical;in the Fe2+/H₂O₂/Na2S2O8 system,OH·and SO4-·played the same important role.It can be concluded that the oxidation system has a better degradation effect for short-chain hydrocarbons,the degradation effect of long-chain hydrocarbons was poor.And combined oxidation system improves the degradation efficiency of medium and long chain hydrocarbons（3）According to response surface design（RSD）experiment,the influence of single factor on the degradation of petroleum hydrocarbons was as follows:Na2S2O8 dosage>Fe2+dosage>H₂O₂ dosage,and the interaction was as follows:H₂O₂ dosage/Na2S2O8 dosage>Na2S2O8 dosage/Fe2+dosage>H₂O₂ dosage/Fe2+dosage.Moreover,the combined oxidation system showed better oxidation ability without adjusting the pH value.When the temperature was 30℃,the oxidation system got the better degradation of petroleum hydrocarbons.If the temperature was too high,the degradation efficiency would be inhibited.