Study On The Removal Efficiency Of Trivalent Arsenic In Water By Hydrogen Peroxide-manganese Dioxide System

In the 21 st century,the problem of arsenic water pollution has gradually come into people's vision.Trivalent inorganic arsenic,as the main arsenic species in natural water bodies,has been widely studied in the removal of surface water and groundwater.In this paper,for the sodium arsenite solution,the preliminary study on the removal of trivalent arsenic by manganese dioxide-hydrogen peroxide system.In this article,three manganese dioxides were synthesized with reference to the methods in the existing literature,and their physical and chemical properties were determined by XRD and SEM analysis.It can be seen that the synthesized solid materials have obvious differences in morphology and crystal form,respectively Prepared manganese dioxide with crystal forms of ?-MnO₂,?-MnO₂and ?-MnO₂;through FTIR,RAM and other analysis,the physical and chemical properties were determined,all of which are mesoporous materials with pore diameters of 3.412 nm and 3.207 nm Compared with 3.406 nm,it has a large specific surface area of 288.487 m2/g,121.487 m2/g and 324.354 m2/g,respectively,with active radicals on the surface.The article examines the effects of various factors on the reaction,including pH,time,temperature,material concentration,and common ion concentrations in water.Several manganese dioxides have higher saturation adsorption capacity: ?-MnO₂: 37.07 mg/g;?-MnO₂: 15.11 mg/g;?-MnO₂: 24.1mg/g.The reaction can reach equilibrium in about 40 minutes,and the reaction is basically complete within 1 hour.The pH value of the system is in the range of 6-8.The system has the best effect of removing arsenic.Peracid and alkali will inhibit the removal of arsenic.Within 15?-45?,there is almost no obvious fluctuation in arsenic adsorption capacity.The high concentration of HCO₃^2-,Cl-,Si O₃^2-and HPO₄^2-significantly inhibited the removal rate of As???,the high concentration of Ca²⁺ and Mg²⁺ slightly inhibited the removal of As???,and the low concentration of Fe³⁺ had a significant effect on the adsorption of arsenic A certain degree of promotion effect,when the Fe³⁺ concentration is higher,it has a certain degree of inhibitory effect on the adsorption of arsenic,and low concentration of humic acid has an inhibitory effect on the adsorption of arsenic.Through the fitting of the data model,it is concluded that ?-MnO₂-H₂O₂ and ?-MnO₂-H₂O₂ adsorption isotherms can better fit the Freundlich model,mainly in the form of multi-molecular layer adsorption;?-MnO₂-H₂O₂ It can be better fitted with the Langmuir model,mainly in the form of monolayer adsorption.The H₂O₂-MnO₂ system absorbs heat during the process of arsenic adsorption,which is an entropy increasing reaction and is judged to be spontaneous.The presence of hydroxyl radicals and superoxide radicals was detected in the system,but the change in the free radical content on the solid surface of manganese dioxide before and after the reaction indicated that the hydroxyl group played a major role.Hydrogen peroxide can oxidize trivalent arsenic to a higher valence state,and manganese dioxide materials have both oxidation and adsorption properties for arsenic.The removal of trivalent arsenic by H₂O₂-MnO₂ system includes the oxidation of As???and the adsorption process of As???and As?V?.The H₂O₂-MnO₂ system has good removal efficiency for trace arsenic pollution in actual water bodies,such as groundwater,Songhua River water,and tap water,and the effect can reach the drinking water standard proposed by the WTO below 10 ug/L;The effluent,where the concentration of organic matter is too high,resulting in poor results.H₂O₂-MnO₂ system for removing arsenic similar to micro-motor with chemical self-driving method,it does not require an external mechanical stirring force,has the advantage of energy saving,the process is green and environmentally friendly,no harmful by-products are produced,it has a higher adsorption capacity for arsenic,and the application prospect is booming.