Photocatalytic degradation of ethiofencarb by a visible light-driven snin₄s₈ photocatalyst

This work reports the preparation and detailed characterization of stannum indium sulfide (SnIn₄S₈) semiconductor photocatalyst for degradation of ethiofencarb (toxic insecticide) under visible-light irradiation. The as-prepared SnIn₄ S₈ showed catalytic efficiency of 98% in 24 h under optimal operating conditions (pH = 3, catalyst dosage of 0.5 g L⁻¹). The photodegradation reaction followed pseudo-first-order kinetics. The major intermediates have been identified using gas chromatography/mass spectrometry.^•O₂⁻ and^•OH radicals appeared to be the primary active species in the degradation process as revealed by scavenger and electronic spin resonance studies, while photogenerated holes had a secondary role in this process. A plausible mechanism involving two routes was proposed for ethiofencarb degradation by SnIn₄S₈ after identifying the major intermediate species: oxidative cleavage of the CH₂-S and the amide bonds of the carbamate moiety. Lastly, SnIn₄ S₈ was found to be efficient, stable, and reusable in treating real water samples in three successive photodegradation experiments. This study demonstrates the prospect of SnIn₄ S₈ photocatalysis in treatment of natural and contaminated water from extremely toxic organic carbamates as ethiofencarb.