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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 ZnSO4/PS ratio, and ions and quenchers, were investigated. High removal efficiency was obtained with a pH of 7 and a ZnSO4/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. Fe2+ promoted the degradation of NOF, whereas other ions inhibited it, with NO3− 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: O2− > ·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. [ABSTRACT FROM AUTHOR]

Abstract A novel ternary composite of graphitic carbon nitride (g-C 3 N 4)/graphene oxide (GO) sheets/BiFeO 3 (CNGB) with highly enhanced visible-light photocatalytic activity toward Cr(VI) photoreduction is prepared and characterized. The characterization and photocatalysis experiments corroborate its reasonable band gap, efficient charge separation and transfer, widened visible-light adsorption, easy solid-liquid separation, good stability and superior catalytic activity of CNGB. Three CNGB samples with different ratios of g-C 3 N 4 and BiFeO 3 (CNGB-1, -2, -3 with 2:4, 3:3, and 4:2, respectively), though possessing different adsorption ability, eventually remove all Cr(VI) ions via photocatalysis within 90 min. The catalytic efficiency of the composite is the highest at pH 2; increases in pH decrease the catalytic ability. The inorganic anions such as SO 4 −, Cl−, and NO 3 − only slightly affects the photocatalytic process. The matching of the band structure between BiFeO 3 and g-C 3 N 4 generates efficient photogenerated electron migration from the conduction band of g-C 3 N 4 to that of BiFeO 3 , which is also facilitated by the electron bridging and collecting effects of GO, and holes transfer from the valence band of BiFeO 3 to that of g-C 3 N 4 , yielding the efficient separation of photogenerated electron-hole pairs and the subsequent enhancement of photocatalytic activity. The research provides a theoretical basis and technical support for the development of photocatalytic technologies for effective application in wastewater treatment and Cr-contaminated water restoration. Highlights • g-C 3 N 4 /graphene oxide/BiFeO 3 (CNGB) ternary assembly is easily prepared. • CNGB shows excellent photocatalysis of Cr (Ⅵ) reduction and easy removal from water. • CNGB shows maximized efficiency at low pH. • CNGB have little chance of electron-hole recombination. • CNGB shows great visible-light response. [ABSTRACT FROM AUTHOR]

Developing efficient and economical photocatalysts was considered as an efficient and economical strategy for pollution remediation. Herein, magnetically separable ZnFe 2 O 4 /CuWO 4 composites (ZW) had been developed via combining ZnFe 2 O 4 with CuWO 4. The composite with a mass ratio of 40% CuWO 4 (ZW-40) performed best, and the tetracycline hydrochloride (TC) removal by adsorption-photocatalysis of ZW-40 reached 86.5%. The photocatalytic degradation rated constant of it was 9.44 × 10−3 min−1, which was approximately 5.04 and 3.28 times compared to the ZnFe 2 O 4 and CuWO 4 samples, respectively. Pseudo-second-order kinetic models could describe well the TC adsorption process, in which chemisorption was the major driving factor, with the maximum adsorption at 23.56 mg g−1. The improved photo-catalytic capability owed to the formation of Z-scheme heterojunctions with ZnFe 2 O 4 and CuWO 4 , which improved the intensity of visible light absorption and enhanced the separation electron-hole pairs as well as the redox capability of the composite. ZW-40 was high stability as its removal ability of TC in different water conditions slightly dropped about 15% after 5 cycles. ZW-40 could effectively remove TC in different water matrix, its removal ability for 40 mg/L was as follows: super-pure water> municipal wastewater> swine farm wastewater. Hence, the complexation of ZnFe 2 O 4 with CuWO 4 provides a valuable strategy to improve the photocatalytic potential for ZnFe 2 O 4 -based catalysts as well as providing a promising pathway for water clarification. • A novel ZnFe 2 O 4 /CuWO 4 (ZW) Z-scheme heterojunction was successfully constructed. • Heterojunction between ZnFe 2 O 4 and CuWO 4 promotes the electron-hole pair separation. • Synergistic adsorption-photocatalysis could more effectively remove tetracycline. • The ZW composite was relatively effective to remove TC from the wastewater. [ABSTRACT FROM AUTHOR]