Remediation Of Typical Organic Pollution Soil Using Persulfate Oxidation Activated By Microwave

With the acceleration of urbanization and adjustment of industrial structures,contaminated sites left over from the relocation of enterprises have become an important issue that restricts the reuse of urban land resources.Such contaminated sites are widely distributed and the number continues to increase,and often show the characteristics of high concentration of compound organic pollution,and complete loss of habitat conditions.Therefore,it is urgent to develop rapid and high-efficient methods to remediate these sites.Compared with the traditional physical-chemical methods,in situ chemical oxidation based on persulfate（PS）repair technology can remove a variety of refractory organic compounds,gradually become the preferred technology for organic contaminated site remediation.However,compared with conventional thermo-activated PS,microwave（MW）heating has the advantages of fast and uniform heating,and relatively lower energy consumption.Therefore,this study is proposed to remediation of typical organic contamination soil by using MW activated PS oxidation.Parathion and pyrene were selected as target pollutants,the degradation rule of them in this system were explored,the optimum conditions were determined,the degradation of possible degradation pathways were proposed,and the toxic change of the product were predicted.Moreover,the removal performance of pyrene was improved by“manganese oxide enhancement-MW/PS”system,and the reaction mechanism was analyzed.Finally,the practicability of the MW/PS system was further verified by using a socket microwave transmitter to treat the actual polycyclic aromatic hydrocarbon（PAHs）contaminated soil,which provided theoretical and technical support for the remediation of organic contaminated sites.The main research work and the results are as follows:Firstly,for the typical organophosphorus pesticide parathion contaminated soil,the effects of PS concentration,MW temperature,soil moisture content on the degradation of parathion were investigated.The experimental results show that the degradation efficiency of parathion reached 90%after treatment at MW temperature of 80℃,PS concentration of 2 mol L^-1,soil moisture content of 20%and initial concentration of 50 mg kg^-1for 90 min.Relatively greater performances for parathion degradation were obtained in a relatively larger PS dosage,higher microwave temperature and appropriate soil moisture.Then,the degradation process conforms to the first-order kinetic model.From the two aspects of radical quenching experiment and EPR analysis,the contribution reactive oxygen species（ROS）were explored.The results indicate that SO₄^·-,^·OH,O₂^·-,and ¹O₂generated in the MW/PS system all participated in the degradation of parathion.Through UV-vis,FTIR,and GC-MS to speculate the possible degradation pathway of parathion.The P-O and P=S bonds in parathion were destroyed after MW/PS oxidation,accompanied by generation of hydroxylated and carbonylated byproducts.The T.E.S.T.toxicity analysis results showed that the toxicity of the by-products of parathion degradation was significantly reduced.In addition,other typical organic pollutants including ethion,phorate,terbufos and pyrene were also successfully degraded by the MW/PS oxidation.Secondly,aiming at the typical polycyclic aromatic hydrocarbons pyrene contaminated soil,a Mn_xO_y-MW/PS combined system was constructed for the remediation of pyrene contaminated soil.The effect of the dosage of Mnx Oy and MW temperature on the degradation effeciency of Pyrene in the combined system was investigated.Significant enhancement performance on pyrene removal was observed after adding manganese oxides,which ranked asβ-Mn O₂>α-Mn O₂>γ-Mn O₂>Mn₂O₃.Pyrene removal efficiency was enhanced from 65.7%to 85.6%within 15 min of treatment whenβ-Mn O₂dosage increased from 0 to 0.1 g.Through radical quenching experiment,EPR,FTIR,and XPS analysis,Mn_xO_yin the MW/PS system improved the production of active substances and converted radical process into non-radical process via conversion of Mn（IV）to Mn（III）and Mn-O-Mn to Mn-O-X.And ¹O₂played significant roles in pyrene degradation.The possible degradation pathways of pyrene was predicted by UV-vis,FTIR,and GC-MS.And the residual toxicity of pyrene and its degradation by-products were predicted.Thirdly,based on the above studies,with the help of socket microwave equipment developed,the MW/PS system was constructed to repair the actual PAHs polluted soil.The effects of PS concentration,MW power on the removal rate of PAHs and MW heating rate were investigated.The results showed that the temperature of MW increased with the increase of MW power,and higher PS concentration and MW power were beneficial to the removal of PAHs.It provides theoretical and technical support for in-situ remediation of contaminated site.