Study On The Removal Of Chlorinated Hydrocarbons In Groundwater By Fenton And Potassium Ferrate

The serious pollutions and potentially harmful of chlorinated hydrocarbons in groundwater has become a hot research scholars. Select the widely existent pollutants (1,1-DCE,TCE and PCE) as the aim pollutants, Fenton reagent and potassium ferrate as oxidants. The removal efficiency, reaction kinetics, main influence factors and dechlorination mechanism of aim pollutants were investigated by batch experiment method. Conclusions are as follows:(1) The removal efficiency of 1,1-DCE, TCE, PCE by Fenton reagent can reach more than 95%. The early oxidations by Fenton reagent followed the pseudo-first order kinetics equations. The reaction rate constant were respectively 1.3432、1.1792、1.0122min-1, the half-life t1/2 were respectively 0.52、0.59、0.68min . The late oxidations by Fenton reagent followed the pseudo- second order kinetics equations. The reaction rate constant were respectively 0.0165、0.1462、0.1166min-1, the half-life t1/2 were respectively 60.51、17.83、11.45min. The maximum removal efficiency of 1,1-DCE, TCE and PCE by potassium ferrate were respectively 67.48%、88.73%、97.37% in the study. The oxidations by potassium ferrate followed the pseudo-first order kinetics equations. The reaction rate constant were respectively 0.0912、0.0675、0.053h-1, the half-life t1/2 were respectively 7.6、10.27、13.08h。.(2) Various pH values had obvious impact on Fenton reagent and potassium ferrate. The degradation rate and removal efficiency was highest at acidic (pH=3) and decreased with either an increase or a decrease in pH. The oxidations rate constants of 1,1-DCE, TCE, PCE by Fenton reagent and potassium ferrate were increased with increased system temperature, and early activation energy Ea by Fenton reagent were respectively 15.55、20.20、26.19 kJ/mol. Activation energy Ea by potassium ferrate were respectively 28.52、45.15、51.13 kJ/mol. Both Fenton reagent and potassium ferrate,ΔH*>0,ΔS*<0,ΔG*>0. The removal reaction rate of 1,1-DCE, TCE, PCE by Fenton reagent had promoted by Fe3+、Cu2+、Mn2+ and inhibited by Cl-、H2PO4-. Under the range of 0~0.2mol/L, the oxidation rate constants of 1,1-DCE, TCE, PCE by potassium ferrate was decreased with the increased iron strength. The early oxidations rate constants by Fenton reagent were increased linearly with the increased concentration of Fe2+. In contrast, the impact of H2O2 on the reaction rate was not obvious than the Fe2 +’s.(3) Under conditions of excess Fenton reagent, there was no organic compound in end products, and there will not be secondary pollution at the end of the reaction. Fenton early reaction is based on the oxidation of Fe4+aq, late reaction is based on the oxidation of·OH. The removal of chlorinated hydrocarbon oxidation by potassium ferrate is the interact results of oxidation and adsorption.