Degradation Of 2,4-dinitrotoluene In Contaminated Groundwater By Vanadium Minerals-activated Persulfate

Vanadium is a ubiquitous element in the environment.The effect of vanadium minerals(vanadium oxide,vanadium-titanium magnetite)on the degradation of organic pollutants by persulfate(PS)and its mechanism are still unclear.In this paper,vanadium trioxide(V2O3),vanadium dioxide(VO2),vanadium pentoxide(V2O5)and vanadium-titanium magnetite were used as research objects,explored the effect of different vanadium minerals/PS system on the degradation of 2,4-dinitrotoluene(2,4-DNT),main research results are as follows:PS activated by vanadium oxide to degrade 2,4-DNT.The degradation performance of 2,4-DNT in different PS/vanadium oxide systems was significantly different.Among them,PS/V2O3 system showed strong oxidation capacity.When the reaction time was 10 h,the degradation efficiency of 2,4-DNT was 77.2%.Compared with iron natural minerals,vanadium oxide has better activation performance.The hydroxyl radical(·OH)was the dominant reactive species for 2,4-DNT degradation by PS/V2O3 oxidation.V2O3 concentration,PS concentration and initial pH were important parameters affecting the degradation of 2,4-DNT.Cl-and humic acid(HA)could accelerate the degradation of 2,4-DNT in PS/V2O3 system,and soil particles would limit the activation of PS.According to the degradation experiment,XRD and XPS characterization data,it was found that there was valence transformation when PS activated by vanadium oxide,Ⅴ(Ⅲ)is oxidized to Ⅴ(Ⅳ),and Ⅴ(Ⅳ)is further oxidized to V(V).Through the continuous electron transfer,persulfate is provided with electrons to generate sulfate radical(SO4·-)and then generate ·OH to degrade 2,4-DNT.PS activated by vanadium-titanium magnetite to degrade 2,4-DNT.The experimental results showed the degradation rate of 2,4-DNT could reach 87.5%after 45 h.The degradation rates of 2,4-DNT were 88.1%and 87.4%when the amount of vanadium-titanium magnetite was 2.0 g·L-1 and 5.0 g·L-1 respectively;the PS concentration is positively correlated with the degradation rate of 2,4-DNT;the PS/vanadium-titanium magnetite system has a wide pH reaction range.·OH is the dominant radical for degradation of 2,4-DNT.The repeatability test of material life showed that the vanadium-titanium magnetite still has high activation performance after repeated utilization,and the degradation rate of 2,4-DNT is reduced by 15.6%.Finally,vanadium-titanium magnetite was characterized by SEM-EDS,FT-IR,XRD and XPS,and the potential mechanism of PS activation by vanadium titanomagnetite was analyzed.Fe(Ⅱ)provides electrons by oxidation reaction,which promotes the formation of SO4·-from S2O82-and subsequent generation of ·OH to degrade pollutants.Oxidation reaction may occur between Ⅴ(Ⅲ)/Ⅴ(Ⅳ)/Ⅴ(Ⅴ),which promotes the reduction reaction of Fe(Ⅲ)to Fe(Ⅱ).