Performance of UV/TiO2/PS, US/TiO2/PS and UV/US/TiO2/PS processes on the diazinon degradation from aqueous solutions and toxicity assay
Samaneh Bakhshaei, Mehrnoush Ghafari, Hasti Daraei
Abstract
Diazinon is a highly dangerous organophosphorus pesticide that conventional treatment methods cannot remove from wastewater. This study aims to investigate ultrasound-chemical-photocatalysis as an eco-friendly method for the effective decomposition of diazinon. The combination of ultrasound and ultraviolet leads to the formation of higher oxidizer agents and faster diazinon decomposition. To assess the efficiency of processes, experiments with AOP based on ultrasound, AOP based on ultraviolet, and a sonophotocatalytic process were conducted. The experiments were done in a glass photoreactor equipped with a UVC lamp and an ultrasonic device. The residual diazinon and intermediates were read by GC-MS. The results indicate that the highest degradation in all processes occurred at Time = 30 min, PS = 3 mmol, and pH = 3. Notably, the sonophotocatalyst process required the lowest catalyst usage. Since the efficiency of photocatalytic processes is significantly influenced by the amount and rate of generation of strong oxidizer radicals; consequently, the highest efficiency was observed in the UV/US/TiO2/PS process. Moreover, the electric energy consumption followed the order US/TiO2/PS> UV/US/TiO2/PS > UV/TiO2/PS. Additionally, with ATU < 1, the toxicity of the wastewater to the environment was found to be low.