Study On The Activity And Loading Efficiency Enhancement Of Simultaneous Catalytic Oxidation Removal Of Ammonium And Manganese By Mn-based Co-oxide Film

In recent years,due to human factors and urban development,groundwater is usually polluted by ammonium and manganese.The concentrations of ammonium and manganese of excessive standard in groundwater are not only harmful to human health,but also harmful to ecosystem.The Mn-based co-oxide film catalytic oxidation method studied by our research group can simultaneously remove ammonium and manganese in drinking water.However,there are still some problems in the technical promotion of production equipment,such as slow preparation speed of Mn-based co-oxide filter media in high alkalinity groundwater,poor activity and load of Mn-based co-oxide film on filter media surface.Starting from improving oxide film performance（activity and loading efficiency of oxide film）,batch pilot-scale experiments were carried out,the effects of different doping amounts（0、0.1and 1.0 mg/L）of two transition metals（copper and cobalt）in high alkalinity groundwater on the removal activity of ammonium and manganese by the Mn-based co-oxide film and its mechanism were investigate,the effect of drying at different temperatures on the loading efficiency of oxide film on the surface of Mn-based co-oxide filter media was studied.The main conclusions of the study are as follows:（1）The most suitable doping method of transition metal（copper,cobalt）was determined to promote the catalytic oxidation activity of ammonium/manganese by Mn-based co-oxide film.When copper doped oxide film,the low concentration（0.1mg/L）copper doping can significantly enhance the ability of oxide film to remove ammonium（ammonium removal efficiency increased from 65%to 100%）.While the high concentration（1.0mg/L）doping has no obvious promoting effect on the removal of ammonium,but will weaken its ability of removing manganese（manganese removal efficiency decreased from 95%to 60%）.When cobalt doped doped oxide film,low concentration cobalt doping can obviously shorten the starting period of the filter column（the effluent ammonium concentration reached the standard on the 6th day.）,but has no promotion effect on the removal of ammonium/manganese.While high concentration cobalt doping has no effect on the removal of manganese,but can enhance the ability of removing ammonium（ammonium removal efficiency increased from 65%to 90%）which is inferior to low concentration copper doping.Therefore,low concentration copper doping is the best transition metal doping method.（2）The mechanism of the effect of transition metal（copper,cobalt）doping on the catalytic oxidation activity of the Mn-based co-oxide film to remove ammonium/manganese was investigated.Copper elements exists in the form of Cu²⁺and Cu⁺in the copper doped filter column.A proper amount of copper doping is beneficial to the formation of Mn³⁺,which promotes the formation of catalytic oxidation ammonium activity.The increase of Mn²⁺ratio caused by large amount of copper doping is the key factor for the decrease of Mn removal ability.Furthermore,the content of Cu⁺in the Filter-Cu_1.0 is higher than that in the Filter-Cu_0.1.Cu⁺does not directly receive electrons and cannot participate in the electron cycle,and competes with the catalytic oxidation of manganese ion for oxygen.For the cobalt doped filter column,the substitution of Co and Mn⁴⁺is beneficial to the formation of Mn³⁺.The doped cobalt exists in the form of Co³⁺,and the Co³⁺/Co²⁺cycle participates in the electron cycle,thus improving its catalytic activity.（3）The best drying method to enhance the loading efficiency of Mn-based co-oxide film was determined.Mn-based co-oxide filter media by drying treatment can obviously shorten the recovery time of filter media activity,enhance the ability of removing ammonium/manganese,and significantly improve the initial film load strength,and the difference between different temperature drying filter media is not obvious.However,the drying has little effect on the initial film quantity of filter media.After 33 days of operation,the film load strength of filter media has been significantly improved and the strength is basically consistent,but at the moment the film load quantity of natural drying filter media is lower than that of other temperature drying filter media.Therefore,for the consideration of activity and film load efficiency of the filter media,the more economical natural or 30℃drying method should be used to deal with the wet filter media after production.