Performance and mechanism of adsorption during synergistic photocatalytic degradation of tetracycline in water under visible (solar) irradiation

The removal of antibiotics from water using solar (visible) light catalytic technology has the advantages of high efficiency, safety, and environmental friendliness. The bismuth tungstate semiconductor catalyst Bi2WO6 exhibits superior performance; however, further research is required to elucidate its synergistic catalytic effects and to better understand its adsorption performance. Herein, a series of modified bismuth tungstate catalysts were prepared by introducing various dispersants. Advanced characterization methods were employed to reveal the structure and composition of the Bi2WO6 catalyst, and the preparation conditions of modified Bi2WO6 were optimized by investigating the adsorption and photocatalytic properties of the catalysts. The synergistic effects of catalyst adsorption and visible light catalysis significantly enhanced the removal of tetracycline through a mechanism whereby the pollutants were enriched on the surface of the catalyst owing to its superior adsorption capacity; this provided a sufficient reaction microenvironment for photocatalytic degradation. The catalyst was loaded onto a sponge surface and subjected to continuous-stream catalysis in a reactor for the degradation of tetracycline-containing wastewater (influent pollutant concentration = 0.8 mg/L). This sponge-loaded Bi2WO6 catalyst was used with a dosage of 0.6 g/L under a light source intensity of 140000 Lux and illumination for 2-h intervals. A hydraulic retention time (HRT) of more than 6 h was observed, and the system achieved a degradation efficiency for trace tetracycline up to 97%, while exhibiting good operational effects after continuous operation for 12 d.