The Study Of Nanoscale Zerovalent Manganese And Zerovalent Manganese-iron Composite Remove Antimony From Water

Antimony is a kind of metalloid element.Antimony and its compounds are dangerous substances with chronic toxicity and potential carcinogenicity.Our country has the richest reserves of antimony in the world,and is also the main part of man-made antimony emissions in the world.With the over-exploitation of mineral resources,the wide application and the increasing demand of antimony will make antimony enter the environment through various ways.The antimony wastewater without treatment could pose a serious threat to ecological environment.Antimony and its compounds can enter the human body through respiratory tract,digestive tract,skin and food chain,causing toxicity to human body.Antimony pollution is the most widespread in water because antimony pollution in air and soil can affect water.Therefore,it is very important to remove antimony from water.In this study,zero-valent manganese and zero-valent manganese-iron composite materials were prepared by sodium borohydride reduction method.The adsorption properties and removal mechanism of matrials for antimony were investigated.Firstly,the zero-valent manganese material（nZVMn）prepared in this study consists of zero-valent manganese as the inner core and manganese oxide（MnO_x）and manganese hydroxyl oxide（MnOOH）as the outer shell.Experimental results show that when the initial pH rang 2 to 11,the removal efficiency of Sb（Ⅲ）and Sb（Ⅴ）were above 94%.The final pH stabilized between 7.7 and 8.5.Common anions in water such as CO₃^2-、SiO₃^2-、PO₄^3-and SO₄^2-,The inhibitory intensity of Sb（Ⅲ）and Sb（Ⅴ）removal efficiency is:PO₄^3->CO₃^2->SiO₃^2->SO₄^2-and PO₄^3->SiO₃^2->CO₃^2->SO₄^2-,respectively.The adsorption of antimony by nZVMnwere more suitable for the Pseudo-second-order kinetic model,and the isothermal adsorption process were more suitable for the Langmuir isothermal model.The maximum adsorption capacities of Sb（Ⅲ）and Sb（Ⅴ）are 377.1 mg/g and 371.8 mg/g,respectively.In order to explore the removal mechanism of antimony,Zeta potential,FTIR and XPS were used to characterize nZVMn.The research analysis indicates that the adsorption of Sb（Ⅲ）by nZVMnincludes electrostatic adsorption,oxidation and surface complexation,and Sb（Ⅴ）were directly complex with hydroxyl groups on the surface of nZVMn.Then,The 2-ZVMn/I composite material（the mass ratio is Mn:Fe=2:1）was prepared by the sodium borohydride reduction method.2-ZVMn/I consists of zero-valent manganese as the inner core and manganese oxide（MnO_x）and manganese hydroxyl oxide（MnOOH）as the outer shell,Zero-valent iron and iron oxide and hydroxyl iron oxide are attached to zero-valent manganese.Experimental results show that when the initial pH between 2 to 11,the removal efficiency of Sb（Ⅲ）and Sb（Ⅴ）were above 96.7%.The adsorption of antimony by 2-ZVMn/I were more suitable for the Pseudo-second-order kinetic model,and the isothermal adsorption process were more suitable for the Frendlich isothermal model.The maximum adsorption capacities of Sb（Ⅲ）and Sb（Ⅴ）are 614.6 mg/g and 241.7 mg/g,respectively.The addition of nZVI to 2-nZVMn/I enhanced the affinity of Sb（Ⅲ）.Coexisting anions have little effect on the removal efficiency of Sb（Ⅲ）.The inhibitory intensity of Sb（Ⅴ）removal efficiency is:PO₄^3-（29）SiO₃^2-（29）CO₃^2-（29）SO₄^2-.Sb（Ⅲ）and Sb（Ⅴ）mainly react with Fe-OH and Mn-OH on the surface of the material to form complexes.Finally,the 2-ZVI/Mncomposite material（the mass ratio is Mn:Fe=1:2）was prepared by the same method.The difference is 2-ZVI/Mnconsists of zero-valent iron as the inner core,iron oxide and hydroxyl iron oxide as the outer shell.Then,manganese oxide（MnO_x）and manganese hydroxyl oxide are attached to zero-valent iron.When the initial pH between 2 to 10,the removal efficiency of Sb（Ⅲ）were above 94.2%and the removal efficiency of Sb（Ⅴ）were above 92.8%.The adsorption of antimony by 2-ZVI/Mnwere more suitable for the Pseudo-second-order kinetic model,and the isothermal adsorption process were more suitable for the Langmuir isothermal model.The maximum adsorption capacities of Sb（Ⅲ）and Sb（Ⅴ）are 707.4 mg/g and 228.9 mg/g,respectively.The inhibitory intensity of Sb（Ⅲ）and Sb（Ⅴ）removal efficiency is:PO₄^3-（29）SiO₃^2-（29）CO₃^2-（29）SO₄^2-.Sb（Ⅲ）and Sb（Ⅴ）mainly react with Fe-OH and Mn-OH on the surface of the material to form complexes.