Simultaneous removal of tetracycline and manganese (II) ions from groundwater using manganese oxide filters: Efficiency and mechanisms

Co-contamination of antibiotics and manganese (Mn2+) prevailing in groundwater enhances the difficulties for water treatment. In this study, a manganese oxide (MnOx) filter media, which was developed for the removal of Mn2+ and ammonium by catalytic oxidation, was adopted to simultaneously remove Tetracycline (TET) and Mn2+ from groundwater. The experimental results show that TET removal is the result of the synthesis of adsorption and oxidation, and the presence of a certain concentration of Mn2+ (1 and 5 mg/L) in the influent significantly reduces the TET removal capacity of the filter media. Similarly, the presence of TET decreases the Mn2+ removal capacity. The breakthrough curves could be fully described with the Thomas model. The surface characteristics and structures of the MnOx filter samples were determined using scanning electron microscopy, Xray diffraction, and X-ray photoelectron spectroscopy. Various analysis results reveal that the high-valence manganese in the crystal lattice of MnOx is consumed during TET removal, which leads to lattice enlargement. However, during the simultaneous removal of Mn2+ and TET, TET consumes high-valence manganese produced by autocatalysis, especially trivalent manganese. The mechanism underlying the simultaneous removal of Mn2+ and TET by the MnOx filter media is revealed in this study. Therefore, this work provides guidance for the prevention and control of antibiotic contaminants during groundwater treatment.