Highly efficient thermo-photocatalytic degradation of tetracycline catalyzed by tungsten disulfide under visible light

Antibiotics are water and soil contaminants causing the development of multi-resistant bacteria, calling for advanced water treatments. For instance, photocatalysis is a promising technology to remove antibiotics at low cost. The tungsten disulfide (WS2) catalyst should be efficient because it possesses a small band gap of 1.35 eV which allows a wide range of light absorption; however, in practice, WS2 shows poor efficiency for antibiotic degradations. Here, we hypothesized that this drawback is due to the insufficient generation of reactive oxygen species. Therefore, we designed a thermo-photocatalytic process with in situ-generated heat under illumination for tetracycline degradation over WS2. We studied catalytic activities, the catalytic mechanism, reactive species, the degradation pathway, and the toxicity of degradation products. Results show that the removal of tetracycline reached 87.4%, which is 2.4 times that of individual thermal catalysis and 3.5 times that of room-temperature photocatalysis. Remarkably, mineralization was enhanced by 7.6 times and 30.9 times, respectively. Moreover, the acute toxicity, developmental toxicity, and mutagenicity of the aqueous solution were reduced after the thermo-photocatalytic degradation. This is the first time that WS2 is demonstrated as an efficient catalyst for visible-light-driven degradation of antibiotics.