Removal Of Fe???,Mn???,and NH₄⁺-N By Using MnO₂ Coated Zeolite

It was very common phenomenon that the concentrations of Fe²⁺,Mn²⁺and NH₄⁺-N from groundwater in Northeast China simultaneously exceed the maximum limit in drinking water,which was seriously affecting the safety of local drinking water.Nano-manganese oxide was loaded on the surface of zeolite,which has broad application prospects in the simultaneous removal Fe²⁺,Mn²⁺and NH₄⁺-N in the groundwater.MnO₂/zeolite nanocomposites were prepared with natural zeolite,potassium permanganate and manganese sulfate by oxidation-reduction precipitation,which were used to simultaneously remove Fe²⁺,Mn²⁺,and NH₄⁺-N from groundwater.To investigate the removal performance and mechanism of Fe²⁺,Mn²⁺,and NH₄⁺-N from groundwater by MnO₂/zeolite nanocomposites,batch static and dynamic experiments were conducted under different environmental conditions at no-oxygen atmosphere using SEM,TEM,Zeta potential,FTIR,and XPS techniques.The variation of microbial polpulations in the column during process was also investigated using high-throughput sequencing technology.The main research findings were listed as follows:?1?To select cost-effective and stable materials,the effect of different synthesis conditions of MnO₂/zeolite on the removal of Fe²⁺,Mn²⁺,and NH₄⁺-N was investigated by simulating groundwater.The results of experimental analysis showed that the best synthesis conditions were 20%MnO₂ loading on zeolite with 24 hours reaction time.?2?The static experimental results showed that the manganese oxide coated natural nanocomposites could be better described with pseudo-second-order kinetic model and Langmuir model.In addition,the maximum adsorption capacities of Fe²⁺,Mn²⁺,and NH₄⁺-N were calculated to be 215.1,23.6,and 7.6 mg·g^-1,respectively.The removal mechanism of NH₄⁺-N from solutions by zeolite was the action of iron exchange,and the adsorption and oxidation catalysis of MnO₂ coated zeolite were responsible for the removal of Fe²⁺and Mn²⁺from solutions.?3?The membrane of biological nitrifying bacteria was carried out,and the intermittent dynamic column was run according to the four stages of adsorption,drainage,biological regeneration,and leaching nitrate.The results of column experiments showed that the simultaneous removal of these contaminants could be obtained with one-stage column,while the effluent concentration was lower than the maximum limits of 0.5mg/L,0.3mg/L and 0.1mg/L in drinking water,respectively.Among them,the removal mechanism of NH₄⁺-N was mainly dominated by the ion exchange and biological nitrification of MnO₂/zeolite column,and the adsorption and catalytic oxidation catalysis were responsible for the removal of iron and manganese.The final conversion products of iron and manganese were composite oxides and hydroxides.?4?The main microbes in the MnO₂/zeolite dynamic column were Proteobacteria,Actinobacteria,Planctomycetes,Nitrospirae and Bacteroidetes.The results indicated that the main functional microbes for ammonia and manganese removal were Nitrospira,Nitrosomonas,and Hyphomicrobium,respectively.