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

• Published in: Applied catalysis. B, Environmental Environmental, 2019-07, Vol.248, p.450-458
• Main Authors: Yu, Jiajie, Kiwi, John, Zivkovic, Ivica, Rønnow, Henrik M., Wang, Tianhe, Rtimi, Sami
• Format: Article
• Language: English
• Subjects: AgxO/FeOx/ZnO magnetic nanotubes; Catalysis; Catalysts; Charge transfer; Fluorescence; Interfacial charge transfer (IFCT); Intermediates; Iron; Irradiation; Kinetics; Light irradiation; Luminous intensity; Magnetic domains; Nanotechnology; Nanotubes; Oxides; Photo-degradation; Photodegradation; Photoelectron spectroscopy; Photoelectrons; Pollutant removal; Pollutants; Reaction kinetics; Reactive oxygen species; Redox reactions; Tetracycline (TC); X ray photoelectron spectroscopy; X-ray fluorescence; XPS; XRD; Zinc oxide; ZnO-FeOx intra-gap states
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2019.02.046

[Display omitted] •Photodegradation of tetracycline (TC) by AgOx-FeOx-ZnO nanotubes is investigated.•Fe seems to introduce intra-gap states in the ZnO NTs enabling e-transport under light.•Redox catalysis was observed leading to the ROS within the TC-degradation time.•The photogenerated ROS were identified using appropriate scavengers 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