Exceeding the permitted manganese (Mn2+) and ammonium (NH4+-N) levels is a frequent seasonal occurrence in a water treatment plant in south China. An iron Fe-Mn complex oxide film was found capable of removing more than 95% of Mn2+ and NH4+-N at a water temperature of 20 °C and an alkalinity level of 30 mg/L. It could remove up to 5.5 mg/L of Mn2+ and up to 3.5 mg/L of NH4+-N in a stable manner. Alkalinity is a crucial factor in the removal process. The morphology, elemental composition, and micro-structure of the oxide film were investigated using a scanning electron microscope, an energy-dispersive spectrometer, a Brunauer-Emmett-Teller specific surface-area analyzer, an X-ray diffractometer, and a Fourier-transform infrared spectrometer. The capacity of the Fe-Mn complex oxide film on the surface of the filter medium increased appreciably as its content and specific surface area increased. This research, which provides a theoretical basis for simultaneous manganese and NH4+-N removal by catalytic oxidation, demonstrates an engineering reference value.
Keywords: alkalinity; catalytic oxidation; iron–manganese complex oxide film; surface water.