Effects Of Coagulants On The Catalytic Properties Of Ironmanganese Co-oxide Filter Films For Ammonium And Manganese Removal From Surface Water

In recent years,the pollution of ammonium and manganese in surface water has become increasingly serious,and the excessive ammonia nitrogen and manganese in drinking water not only poses a threat to human health,but also has a negative impact on the water treatment process.Therefore,it is of great significance to study the removal of ammonium and manganese in surface water for the safety of drinking water in China.This project is based on the chemical catalytic oxidation method proposed in recent years to achieve the removal of ammonium and manganese from surface water.A pilot-scale experiment was carried out with two parallel filter columns to compare the effects of three different coagulants?ferric chloride?FeCl₃?,polymerization ferric chloride?PFC?,and polymeric aluminum ferric chloride?PAFC??on the catalytic oxidation of an iron–manganese?Fe-Mn?co-oxide filter film for NH₄⁺and Mn²⁺removal from surface water,and the effect of bicarbonate alkalinity on the activity of Fe-Mn co-oxide for ammonium and manganese removal was studied.In addition,the mechanism of coagulant affecting filter media activity and alkalinity recovery filter media activity were discussed.The main conclusions of this study are as follows:?1?The optimal coagulant for the pre-coagulation stage of the Fe-Mn co-oxide filter column in surface water treatment was identified.FeCl₃ was not conducive to the removal of NH₄⁺and Mn²⁺,PFC had a negligible effect on the catalytic activity of the Fe-Mn co-oxide for NH₄⁺and Mn²⁺removal.With PAFC,the NH4⁺removal efficiency of filter began to decrease after 50 days,but the catalytic activity of the Fe-Mn co-oxide for Mn²⁺removal remained unchanged.Therefore,FeCl3 and PAFC are not recommended to be used as coagulants when the Fe-Mn co-oxide filter medium is applied to remove NH₄⁺and Mn²⁺from surface water.PFC,based on removal performance over time,was concluded to be the most suitable coagulant among the three tested.?2?The mechanism of the effect of different coagulants on the catalytic oxidation ammonium activity of Fe-Mn oxide film was investigated.Analysis of the water quality parameters and filter media characterization indicated that FeCl₃ was not favorable for the removal of NH₄⁺and Mn²⁺mainly due to the decrease in pH after its hydrolysis.The main reason for the decrease in NH4⁺removal activity with PAFC might have been the structural change caused by Al.Specifically,the difference in bonding interactions between aluminum?Al?and the Fe-Mn co-oxide with different running times may have caused the difference in activity.?3?The influence of alkalinity on catalytic efficiency of deactivated filter media and the recovery mechanism of catalytic activity were clarified.The removal effect of filter under different alkalinity showed that the addition of alkalinity significantly promoted the activity of the Fe-Mn co-oxide.The ammonium and manganese removal efficiencies of the filter increased from 40%to 95%and 85%to100%,respectively.After alkalinity was no longer added,the activity of the filter column remained.Further characterization analysis of the Fe-Mn co-oxide filter film showed that after alkalinity was added,the accumulation of aluminum on the filter media surface decreased and the oxide functional groups changed.This was due to the action of bicarbonate and the residual aluminum salt coagulant in the filter,which caused the loss of Al from the surface of the filter media and weakened the influence of the aluminum salt coagulant on the activity of the Fe-Mn co-oxide;hence,the activity was recovered.