Effect And Mechanism Of Arsenic Adsorption By Zirconium-Manganese Oxide Nanocomposite Supported On Activated Charcoal

Arsenic,as a "three causes" substance(teratogenic,carcinogenic,mutagenesis),the treatment and prevention of its pollution has been the focus of scientific research scholars.Adsorption is one of the most common water treatment technologies and is widely used in the removal of various pollutants.Zirconia is an ideal adsorbent material for As(?),which can remove the target pollutants through electrostatic attraction and ligand exchange process.While manganese dioxide has a good removal effect on As(?)due to its strong oxidation ability.However,they are easy to agglomerate during the preparation process.In this study,a zirconium-manganese oxide nanocomposite supported on activated charcoal(Zr/Mn/C)was prepared.This material combines the advantages of activated charcoal,Zr-based and Mn-based materials,and solves the problems of easy agglomeration and difficult solid-liquid separation.The Zr/Mn/C nanocomposite was characterized and used as adsorbent in water containing arsenic.The adsorption mechanism and factors which will affect the adsorption process were studied,such as:pH values,initial concentrations,adsorbent dosage,coexisting ions and so on.The results are as follows:(1)The Zr/Mn/C nanocomposite was successfully prepared by co-precipitation-hydrothermal method.The results of SEM and TEM analysis showed that the Zr-Mn oxide nanoparticles were successfully loaded and evenly distributed on the surface of the supported activated charcoal.The Zr/Mn/C is an ideal adsorbent due to its nano-structure.According to the results of XRD,Raman and BET analysis,it was clear that the Zr/Mn/C nanocomposite is amorphous which has larger pores and more adsorption sites than crystalline materials.The specific surface area of Zr/Mn/C is 264.04 m2/g.(2)Single factor experimental method was adopted to study the removal mechanism of As(V).It was found that the Zr/Mn/C nanocomposite had the largest adsorption capacity when the pH=6.0.The experimental data were fitted into pseudo-second-order kinetic model and Langmuir adsorption isotherm model well.Indicating that chemical adsorption plays a dominant role in the adsorption process,and the whole reaction is easy to carry out.The optimum dosage of Zr/Mn/C is 0.4g/L,it has a high removal rate and a large adsorption capacity under this condition.At high initial concentration of the As(V)(30mg/L),the saturated adsorption capacity of the nanocomposite can reach to 95.60mg/g;at low initial concentration of As(V)(<9mg/L),the residual concentration after adsorption could reach the standard of drinking water(<10?g/L).The results of XPS and FTIR analysis showed that the adsorption mechanisms were as follows:the non-specific adsorption through electrostatic attraction and the specific adsorption by ligand exchange.Moreover,the material has strong anti-interference and is suitable for complex water environment.It can be seen that Zr/Mn/C nanocomposite has a good adsorption effect on As(?)and a good application prospects(3)Single factor experimental method was also adopted to study the removal mechanism of As(?).It was found that the Zr/Mn/C nanocomposite had the largest adsorption capacity when the pH=10.0.The experimental data were fitted into pseudo-second-order kinetic model and Langmuir adsorption isotherm model well.Indicating that chemical adsorption plays a dominant role in the adsorption process,and the whole reaction is easy to carry out.The optimum dosage of Zr/Mn/C is 0.4g/L,it has a high removal rate and a large adsorption capacity under this condition.At high initial concentration of the As(?)(30mg/L),the saturated adsorption capacity of the nanocomposite can reach to 132.28mg/g;at low initial concentration of As(?)(<lmg/L),the residual concentration after adsorption could reach the standard of drinking water(<10?g/L).The results of XPS and FTIR analysis showed that the adsorption mechanisms were as follows:the non-specific adsorption through electrostatic attraction,the specific adsorption by ligand exchange and redox reaction.Moreover,the material has strong anti-interference and is suitable for complex water environment.It can be seen that Zr/Mn/C nanocomposite has a good adsorption effect on As(III)and a good application prospects.