[Removal of Fe(Ⅱ), Mn(Ⅱ), and NH4+-N by Using δ-MnO2 Coated Zeolite].

δ-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 performance and mechanism of Fe2+, Mn2+, and NH4+-N removal from groundwater by δ-MnO2/zeolite nanocomposites, static batch experiments were conducted under different environmental conditions in a zero-oxygen atmosphere using SEM, TEM, Zeta potential, FTIR, and XPS techniques. The experimental results showed that the manganese-oxide-coated natural zeolite was δ-MnO2, and Fe2+, Mn2+, and NH4+-N adsorption on the δ-MnO2/zeolite nanocomposites could be best described with the pseudo-second-order kinetic model and the Langmuir model. In addition, the maximum adsorption capacities of Fe2+, Mn2+, and NH4+-N were calculated to be 215.1, 23.6, and 7.64 mg·g-1, respectively. The removal mechanism of NH4+-N from the solutions by zeolite was via the action of ion exchange, and the adsorption and oxidation catalysis of δ-MnO2-coated zeolite were responsible for the removal of Fe2+ and Mn2+. This research indicates that δ-MnO2/zeolite nanocomposites could be used as highly efficient adsorbents to simultaneously remove Fe2+, Mn2+, and NH4+-N from water.