Accelerated ZnMoO4 photocatalytic degradation of pirimicarb under UV light mediated by peroxymonosulfate
Résumé
This paper reports the optimized synthesis of zinc molybdates by the hydrothermal method and the combination of ZnMoO4 and peroxymonosulfate (PMS) under UV irradiation for the degradation of pirimicarb. The as‐prepared ZnMoO4 photocatalyst was characterized using X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy and UV–visible diffuse reflectance spectroscopy. The effects of operational parameters in the ZnMoO4/PMS/UV system were evaluated and the results indicated the highest performance is achieved with pH = 9.0, 1 mM PMS and 1 g l−1 ZnMoO4. The degradation efficiency of pirimicarb was 98% after 3 h in the photocatalytic process. A photodegradation mechanism is proposed based on scavenger and electron spin resonance studies to decide the main active species and by using chromatography–mass spectrometry to identify the major intermediates. Pirimicarb degradation is found to be mainly driven by holes and •O2− radicals, with the contribution of •OH and SO4•− radicals enhancing the process in the tested catalytic system. The mechanism is proposed involving two routes, dealkylation and decarbamoylation. Lastly, the zinc molybdate photocatalyst is shown to be stable, reusable and efficient in the removal of pirimicarb from real water samples in the presence of PMS, demonstrating potential application in the treatment of contaminated and/or environmental water.