Degradation of dichlorvos using hybrid advanced oxidation processes based on ultrasound

Degradation of dichlorvos pesticide has been investigated in an ultrasonic bath having operating power of 150 W and operating frequency of 36 kHz with a capacity of 7 L. All the experiments have been performed using 20 mg/L solution of commercially available dichlorvos at an operating pH of 3 under ambient conditions. Different combined treatment processes such as ultrasound (US)/TiO2, solar/TiO2, US/solar/TiO2, US/H2O2, US/Fenton and US/ozone have been applied with an objective of achieving effective and complete degradation of dichlorvos. The removal of dichlorvos was found to be significant in the case of TiO2/solar (78.42%) and US/Fenton (81.19%) in 2 h treatment as compared to only ultrasound (6.4%) or only TiO2 (3%) which is a clear indication of the efficacy of combined treatment processes. Complete degradation of dichlorvos was obtained by using combination of ozone and ultrasound. TOC analysis at optimum conditions was also performed to quantify the extent of mineralization and it has been observed that a maximum of 93% TOC reduction is obtained in the case of combination of ozone and ultrasound. Integral method of analysis was followed and it has been observed that pseudo-first order kinetics explains the degradation reaction very well. The present work has conclusively established that cavitation in the presence of additives can be effectively used for complete removal of dichlorvos pesticide at pilot scale operation.