Study On Preparation Of High Active Manganese Oxide And Its Removal Of Manganese And Ammonia Nitrogen In Drinking Water

Manganese and ammonia nitrogen are currently the main pollutants in drinking water sources in our country.The pollution situation is becoming more and more serious,and they have great harm to human health and the environment.Manganese oxide has the characteristics of strong adsorption activity,large specific surface area,and good catalytic performance.As an active material that can efficiently remove manganese and ammonia nitrogen in water,it has received extensive attention^[1].However,how to prepare and select high-activity manganese oxide still needs to be solved urgently.In this thesis,by preparing manganese oxides with different structural characteristics and analyzing their structures,the effects of oxidation conditions and doping ions on the removal of manganese and ammonia nitrogen from manganese oxides in water are explored,and the effects of manganese oxides on manganese and ammonia in water are analyzed.The removal mechanism of ammonia nitrogen.The main conclusions are as follows:（1）Different oxidation conditions have a great influence on the structure and activity of manganese oxide.The samples prepared with KMnO₄as the oxidant under acidic,alkaline and neutral conditions are all Akhteskite type MnO₂（ε-MnO₂）,which has low crystallinity and large specific surface area;while the samples prepared with O₂as the oxidant are Hausmannite type Mn₃O₄^[2]has high crystallinity,dense oxide surface and small specific surface area.The removal efficiency of manganese oxide on ammonia nitrogen and manganese is affected by the p H,temperature and ionic strength of the water.Among them,the manganese oxide prepared by KMnO₄as the oxidant under alkaline conditions has the highest removal efficiency of ammonia nitrogen and manganese.（2）Doping ions such as Na⁺,Mg²⁺,Ca²⁺and Fe³⁺also have a greater impact on the structure and activity of manganese oxide.Doping ions does not change the oxide crystal structure.Under the action of different doping ions,the samples prepared with KMnO₄as the oxidant are still Akhtenskite type MnO₂;but the specific surface area and surface morphology of manganese oxide under different doping ions,Raman spectra and Zeta potential all showed significant differences.Among them,the incorporation of Fe³⁺makes the sample have a larger specific surface area,but its surface zeta potential is higher,so the corresponding manganese oxide removal activity is the lowest;the incorporation of Ca²⁺makes manganese oxide have a large specific surface area and a low isoelectric point,etc.Features,showing the best manganese and ammonia nitrogen removal activity.（3）The research results of the mechanism show that the removal of ammonia nitrogen by manganese oxide is only adsorption,and the removal of manganese includes both adsorption and catalytic oxidation capabilities.The removal of NH₄⁺by manganese oxide is mainly through the electrostatic adsorption of Mn-O^-on the surface of the oxide.Mn²⁺can be removed by electrostatic adsorption with Mn-O^-and ion exchange with H in Mn-OH on the oxide surface at the same time;at the same time,the adsorbed Mn²⁺can be further catalyzed into new manganese oxide.Among them,manganese oxide doped with Ca²⁺has the highest manganese catalytic activity.