Efficient photocatalytic treatment of pesticide industry wastewater using TiO2/ZSM-5 zeolite hybrid photocatalysts

Abstract

The widespread agricultural activity and increased pesticide use resulted in water source pollution due to their toxicity. The removal of pesticides from the wastewater can save water resources and is therefore an important research direction. In particular, the treatment of pesticide industry wastewater is a challenging task. The efficiency of two hybrid photocatalysts based on TiO<inf>2</inf> and ZSM-5 zeolite was investigated for the removal of widely used herbicide clomazone from an aqueous solution and a mixture of herbicides from an industrial wastewater sample. Eco-friendly materials, prepared using an ultrasound solid-state dispersion method, contained 20 wt% of commercial P25 TiO<inf>2</inf> Degussa nanoparticles and TiO<inf>2</inf> nanocrystals synthetized from nanotubes (TNT) as one component and ZSM-5 zeolite (Si/Al = 40) as the other one. The hybrid photocatalysts were characterised combining X-ray powder diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy and low temperature nitrogen adsorption. Gas chromatography coupled with mass spectrometry was employed for investigation of the occurrence and removal of pesticides. The industrial wastewater sample contained clomazone as the major contaminant along with terbuthylazine, metamitron, metribuzin, bentazon, metalaxyl, haloxyfop-methyl, mefenpyr-diethyl, dithiocarbamates and co-formulants. A complete removal of clomazone from an aqueous solution was achieved in the presence of P25–ZSM5, while 96.4% removal is observed when using TNT–ZSM5 photocatalyst after 60 min of sun simulated irradiation. TiO<inf>2</inf>/ZSM-5 zeolite hybrid photocatalysts proved to be efficient, as total pesticide removal from the industrial wastewater of 86.7% was achieved for P25–ZSM5 and 68.6% for TNT–ZSM5 after 180 min of irradiation.