Hydrothermal nanoarchitectonics of Z-scheme g-C3N4/Bi2WO6 heterojunction with enhanced adsorption and photocatalytic activity for fluoroquinolone antibiotics removal: Kinetics, mechanism and degradation pathway

The heterogeneous photocatalysis provided a sustainable and environmentally friendly approach for rapid elimination of fluoroquinolone antibiotics in water, but the low specific surface area and adsorption capacity of traditional photocatalysts restricted their interfacial reactions with contaminants. Herein, a novel g-C3N4/Bi2WO6 photocatalyst with remarkable adsorption capacity was synthesized through hydrothermal method. The characterization analysis demonstrated that layered g-C3N4 were uniformly assembled on Bi2WO6 microsphere surface and formed tight g-C3N4/Bi2WO6 heterojunction. Compared to the pure g-C3N4 and Bi2WO6, g-C3N4/Bi2WO6 had larger specific surface area, and the adsorption efficiency to norfloxacin (NOR) and levofloxacin (LEV) could reach 54.53% and 43.73% under 40-min dark condition. The adsorption behavior was consistent with pseudo-second-order model, demonstrating that the adsorption process was mainly dominated by chemical adsorption. The NOR and LEV removal efficiency increased to 85.75% and 85.82% after 120-min visible-light irradiation. The enhanced photocatalytic activities were ascribed to the improved visible-light utilization and suppressed carriers recombination owing to the formation of Z-scheme heterojunction. Holes and •O2- played major roles during the photocatalytic degradation of NOR and LEV. Three main degradation pathways of NOR were proposed, and the acute toxicity and bioaccumulation of its intermediates declined after photocatalytic degradation.