Electrodeposited manganese oxides as efficient photocatalyst for the degradation of tetracycline antibiotics pollutant

One of the important environmental challenges of the 21st century is the effective removal of pollutants from the aquatic environment. In this study, electrodeposited manganese oxides (Mn_yO_x) films were applied as visible-light-driven photocatalyst for the removal and mineralization of Tetracycline (TC) antibiotics. The photocatalytic activity of as-deposited and annealed Mn_yO_x was tested at different pH values using LED visible illumination, resulting in 92.4 % of TC mineralization efficiency after 180 min for the best performing manganese oxide. Quenching experiments showed that hydroxyl radicals (OH) are the main active species responsible for the TC degradation. The photocorrosion of Mn_yO_x has been studied by quantifying the concentration of the dissolved manganese cations during the photocatalytic experiments. By comparing the catalyst mass loss with the % of TC mineralization, we revealed that the degradation of the oxide surface structure is the factor that, more than the photocorrosion, is limiting the photocatalytic activity of Mn_yO_x films. Finally, the photocatalytic mechanism of TC mineralization is proposed based on the detection of the intermediates species of the mineralization process by High-Performance Liquid Chromatography Mass-Spectroscopy. The facile synthesis process and the superior mineralization rate can open up a new approach for the possible large-scale utilization of electrodeposited Mn_yO_x films as an effective visible light photocatalyst.