Photocatalytic degradation of thiobencarb by a visible light-driven MoS₂ photocatalyst

In this study, molybdenum disulfide (MoS₂) microsphere was prepared and employed as a visible-light catalyst for the photocatalytic degradation of thiobencarb (TBC), a carbamate pesticide. The as-prepared MoS₂ photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). TBC elimination using MoS₂ proved to be efficient and practical in both deionized and environmental water samples. This photocatalytic method presented a set of advantages over other TBC removal processes such as using visible light source without the need of costly additives (e.g.·H₂O₂). Optimization studies of this process showed that the degradation efficiency could reach 95% in 12 h at a pH range of 6–9. Further, the effect of anions (Cl⁻ and NO₃⁻) was minor on the photocatalytic activity of MoS₂. Experiments using radical scavengers indicated that hydroxyl radicals and holes are the prevailing reactive species involved in this process. Three possible photodegradation pathways were proposed based on the major intermediates as verified by gas chromatography/mass spectrometry technique. The practicality of this MoS₂ photocatalyst was validated by its use in the removal of TBC from real water samples and by its stability and reusability in three successive runs, evidencing its prospective applications in the treatment of environmental water and contaminated wastewater samples.