Quantification of the local magnetized nanotube domains accelerating the photocatalytic removal of the emerging pollutant tetracycline

Abstract

Evidence is presented for the enhanced photodegradation of tetracycline (TC) by AgxO/FeOx/ZnO nanotubes (NTs) compared to AgxO/ZnO nanotubes under low-intensity solar light irradiation. A higher amount of the local magnetic domains with random orientation in the AgxO/FeOx/ZnO NTs lead to a faster TC-degradation. Fe introduces intra-gap states in the ZnO NTs facilitating the e-transport under light. The AgxO/FeOx/ZnO nanotubes were observed to present predominantly semiconductor behavior during the light induced TC-degradation. The nature of the interaction between non-polarized photos with the local domains due the addition of Fe is discussed. By X-ray photoelectron spectroscopy (XPS) redox reactions were observed on the nanotube surface NTs leading to the reactive oxygen radical species (ROS). The ROS-intermediates were identified by appropriate scavengers. Fast TC-degradation kinetics was attained by a catalyst with a composition AgOx(5.8%)FeOx(21.9%)ZnO (72.3%) as determined by X-ray fluorescence (XRF). A scheme for the interfacial charge transfer (IFCT) between the oxides on the nanotube surface is presented. Magnetized nanotubes present a practical potential in environmental cleaning avoiding the high cost separation of the catalyst from the reaction media at the end of the process