Systematic Study On Remediation Of Petroleum Hydrocarbon Contaminated Soil Based On NZVI/CA/Air Method

At present,petroleum hydrocarbon pollution is becoming a more serious problem.When petroleum pollutants enter into the soil,they will seriously affect the quality of soil environmental and have great harm to the ecological environment and human health.The advanced oxidation processes（AOPs）has attracted extensive attention in the remediation of organic contaminated soil due to its high treatment efficiency and short remediation time.The effect of soil remediation by traditional AOP_S is affected by the type and concentration of oxidants,and the excessive use of oxidants will harm the structure and physical and chemical properties of soil.This paper proposes an environmentally friendly method—n ZVI/CA/Air method.In the n ZVI/CA/Air method,hydrogen peroxide can be generated by Fenton-like reaction of Fe⁰/O₂,and Fe²⁺and H₂O₂continue to react to produce active oxides（ROS）such as·OH,which can remove organic pollutants.Citric acid can generate more ROS by dissolving metals and destroying the oxidation process of iron ions.This method can reduce the secondary pollution caused by the addition of H₂O₂,and has less harm to the soil.This article uses n ZVI/CA/Air method to remediate petroleum hydrocarbon contaminated soil,by exploring the effects of n ZVI dosage,CA dosage,reoxygenation method,soil organic matter and other factors on the remediation efficiency,we explore the reaction mechanism of n ZVI/CA/Air method in the process of remediation of petroleum hydrocarbon contaminated soil.Finally,the feasibility of n ZVI/CA/Air method combine with chemical washing method/persulfate oxidation method to remediate petroleum hydrocarbon contaminated soil was also discussed.The research conclusions are as follows:（1）When using nZVI alone to remediate petroleum-hydrocarbon contaminated soil,the removal efficiency of TPHs in soil samples increases first and then decreases with the increase of n ZVI dosage.When the dosage of n ZVI was increased from 0g to 1g,the removal efficiency of soil A and soil B increased by 7.4%%and 3.8%,respectively.n ZVI can degrade petroleum hydrocarbons in soil,but the removal efficiency is low.Iron and organic matter in the soil can also degrade organic pollutants.（2）The nZVI/CA/Air method can degrade organic pollutants by generating hydroxyl radicals（·OH）and superoxide radicals（·O₂^—）,and the remediation efficiency of n ZVI/CA/Air method is better than n ZVI alone.When the dosage of n ZVI was 0.5g,the remediate efficiency of soil A and soil B when using n ZVI/CA/Air method was improved by 14.8%and 12.6%respectively.The increase of n ZVI and CA dosage can improve the remediation effciency of petroleum contaminated soil,while excessive n ZVI and CA will affect the reaction efficiency between ROS and organic pollutants.Both light and aeration conditions can improve the removal efficiency of n ZVI/CA/Air method.The concentration of organic matter in the soil is directly proportional to the removal efficiency of TPHs.（3）The remediation efficiency of nZVI/CA/Air method combined with chemical washing method is better than using n ZVI/CA/Air method alone.For soil A,the two remediation methods of first solubilization then oxidation and first oxidation then solubilization under aeration conditions increased by 35.0%and 34.7%compared with n ZVI/CA/Air method.For soil B,two remediation methods increased by 9.4%and10.5%respectively.When the n ZVI/CA/Air method and the chemical washing method are combined for remediate petroleum-hydrocarbon contaminated soil,aeration and first solubilization then oxidation should be adopted.（4）The remediation efficiency of nZVI/CA/Air method combined with persulfate oxidation method is better than using n ZVI/CA/Air method alone.For acid soil A,when the PS concentration is 5g/L,the remediation efficiency of petroleum hydrocarbon contaminated soil under the conditions of n ZVI and PS simultaneous dosing and n ZVI followed by PS are 49.2%and 56.3%,respectively.For alkaline soil B,the remediation efficiency of petroleum hydrocarbon contaminated soil increased to 51.2%and 58.6%in two cases.The remediation efficiency of PS after n ZVI is better than that when n ZVI and PS simultaneously added.