A Study On The Degradation Of Trichloroethylene And Hexavalent Chromium By Using Bentonite-supported Nanoscale Fe/Ni

The injection of nanoscale zero valent iron(nZVI)into groundwater has been newly developed as an in-situ groundwater remediation technology in recent years due to its high capacity for removal of heavy metals and chlorinated organics.But nZVI was easy to be oxidized and aggregated and showed poor activity and mobility,which limited the implication of nZVI.In this study,the bentonite-supported nanoscale Fe/Ni bimetal(B-Fe/Ni)was successfully synthesized by the loading and doping modification methods.The morphology and and physicochemical properties of B-Fe/Ni were characterized,and the batch experiments of adsorption of hexavalent chromium(Cr(?))and degradation of trichloroethylene(TCE)were conducted to investigate the performance and mechanisms of B-Fe/Ni on the removal of coexisting TCE and Cr(?).B-Fe/Ni was also used in advanced oxidation technology to activate persulfate for TCE degradation,in order to evaluate the implication potential of B-Fe/Ni in groundwater remediation..Here are the main achievements:The characterization of B-Fe/Ni by TEM-EDS,XPS,DLS/Zeta demonstrated that the chain-like B-Fe/Ni particles had enhanced dispersity than nZVI,which was aggregated in bulk.Iron was existed in B-Fe/Ni as Fe~0,Fe(II)and Fe(III),which composed the Fe~0 core-Fe oxides shell structure.B-Fe/Ni had smaller hydrodynamic size in well dispersion and slower sedimentation rate than nZVI under the efffect of bentonite.Coexisting TCE and Cr(?)were simultaneously and more efficiently removed by B-Fe/Ni compared to nZVI.The degradation of TCE by B-Fe/Ni was decreased with the rising initial concentration of Cr(?),while TCE showed little effect on the removal of Cr(?),because that the generated Fe-Cr co-precipitations from the fast interaction of B-Fe/Ni with Cr(?)covered the active sites on the particle surface of B-Fe/Ni mitigating the degradation of TCE.The increased initial concentration of B-Fe/Ni facilitated the degradation rate of TCE,and the presence of humic acid did not influence the removal of coexisting TCE and Cr(?).B-Fe/Ni showed better catalytic activity than nZVI,Fe/Ni and B-Fe,which could effectively activate persulfate to degrade TCE in alkalescent groundwater.The increased dose of persulfate and the presence of dissolved oxygen could accelerate the reaction.B-Fe/Ni has wide implication prospect in situ groundwater remediation with both great reductive adsorption capacity and catalytic oxidation ability.