Synergistic adsorption-photocatalytic degradation effect and norfloxacin mechanism of ZnO/ZnS@BC under UV-light irradiation
Wen Liu, Tianpei He, Yonghong Wang, Ning Ge, Zhenggang Xu, Xiaoyong Chen, Xinjiang Hu, Yaohui Wu, Yunlin Zhao
Abstract
Abstract Norfloxacin (NOF) is an environmentally harmful and ubiquitous aquatic pollutant with extensive production and application. In this study, a novel composition named carbon-based composite photocatalytic material of zinc oxide and zinc sulphide (ZnO/ZnS@BC) was successfully obtained by the impregnation-roasting method to remove NOF under UV-light. Scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive spectrometer characterised the composition. ZnO/ZnS was successfully decorated on the surface of biochar (BC). The pH, the ZnSO 4 /PS ratio, and ions and quenchers, were investigated. High removal efficiency was obtained with a pH of 7 and a ZnSO 4 /PS ratio of 1:1, and the removal ratio of NOF reached 95% within three hours; the adsorption and degradation ratios reached 46% and 49%, respectively. Fe 2+ promoted the degradation of NOF, whereas other ions inhibited it, with NO 3 − showing the strongest inhibitory effect. Three reactive species (tert-butanol, quinone, and ammonium oxala) were identified in the catalytic system. The decreasing order of the contribution of each reactive species was: O 2 − > ·OH − > h + . Additionally, a recycling experiment demonstrated the stability of the catalyst; the catalytic degradation ratio of NOF reached 78% after five successive runs. Therefore, ZnO/ZnS@BC possessed strong adsorption capacity and high ultraviolet photocatalysis ability.