铁锰二元氧化物改性粉煤灰对地下水中砷的吸附特性OA北大核心CSTPCD

High arsenic groundwater is widely distributed in inland basins and river deltas in China,and ad-sorption method has been widely used as a simple and efficient method for arsenic removal.However,the adsorption capacity of most adsorbents for As(Ⅲ)is weaker than that of As(Ⅴ),so it is of positive signifi-cance to develop efficient adsorption with the coupling effect of oxidation and adsorption.The fly ash modi-fied with Fe-Mn binary oxide(FMFA)was prepared by co-precipitation,and its adsorption properties and mechanism for As(Ⅲ)/As(Ⅴ)were studied.The adsorption performance of FMFA on As(Ⅲ)/As(Ⅴ)in solution was investigated by batch experiment.The surface morphology and structure of FMFA were ana-lyzed by XRD,SEM and BET,and the changes of elements and functional groups on FMFA surface before and after adsorption were analyzed by XPS and FT-IR.The experimental results show that both the Fe oxide and Mn oxide are loaded on the surface of fly ash in amorphous form,which greatly increases the spe-cific surface area of FMFA(up to 166.77 m2/g),and provides more active sites for As(Ⅲ)/As(Ⅴ)adsorp-tion.In neutral condition,the adsorption capacities of FMFA for As(Ⅲ)and As(Ⅴ)are 68.19 mg/g and 24.42 mg/g,and the adsorption isotherm model of As(Ⅲ)/As(Ⅴ)conforms to Freundlich model.The ad-sorption process of As(Ⅴ)follows the qseudo-second-order kinetic model,and the As(Ⅲ)is more consis-tent with the Elovich model.The alkaline environment with initial pH＞9 is not conductive to the adsorp-tion of As(Ⅲ)/As(Ⅴ)by FMFA which is more stable in the range of initial pH=5～9.The effect of the coexisting oxygen-containing anions on competitive adsorption of As(Ⅲ)/As(Ⅴ)in water is PC43-＞HCO3＞SO2-.FMFA can effectively remove arsenic from groundwater samples without causing seconda-ry pollution of iron and manganese,and has good recycling capacity.During the adsorption of As(Ⅲ)by FMFA,manganese dioxides mainly plays the role of oxidation and iron oxide plays the role of adsorption,and arse-nic is adsorbed by exchanging with metal active hydroxyl groups on the FMFA surface to form inner complex.This paper has successfully prepared a new green economic adsorbent which can effectively remove As(Ⅲ)/As(Ⅴ)from groundwater,which is of great significance to ensure the safety of drinking water for residents.