Efficiency and mechanism of removing ammonium from groundwater by manganese oxides with different crystal forms
The efficiency and mechanism of removing ammonium from groundwater by manganese dioxide with three different crystal forms(α-MnO2,γ-MnO2,δ-MnO2)were studied,and the practical application efficiency of the filter column filled with γ-MnO2 coated filter media was investigated.The experimental results showed that γ-MnO2 possessed the best catalytic oxidation activity for removing ammonium(γ-MnO2>α-MnO2>δ-MnO2),5mg/L NH4+-N could be completely removed on the 20th day,and the accumulation time of nitrite was the shortest and the peak value was the lowest.The filter column filled with γ-MnO2 coated filter media could quickly(the 6th day)form excellent catalytic activity,when the influent NH4+-N was 2.0mg/L,the effluent NH4+-N was lower than the standard limit(<0.5mg/L).Combined with the characterization analysis,it was found that the highest catalytic activity of γ-MnO2 was mainly due to its higher average manganese oxidation state and abundant surface hydroxy oxygen,and its electron transport ability was the strongest.This study provides theoretical guidance for the application of manganese oxides in the field of ammonium removal from drinking water.γ-MnO2 coated filter media has good catalytic oxidation stability and efficiency,and provides a new perspective for the preparation of catalytic oxidation active filter media in practical engineering.
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