Synergistic effects of the combined use of ozone and sodium percarbonate for the oxidative degradation of dichlorvos

Dichlorvos or 2,2-dichlorovinyl dimethyl phosphate (DDVP) is a chlorinated organophosphorus pesticide which is frequently detected in the aqueous environment. In this study, an environmentally friendly and highly efficient oxidant, i.e., sodium percarbonate (SPC, Na2CO3 center dot 1.5H(2)O(2)) was introduced to an ozonation process for the degradation of dichlorvos (DDVP). Experimental results revealed an enhancement of DDVP degradation efficiency via the O-3/SPC process compared with O-3 alone due to the generation of reactive species (OH- and CO3 center dot-) under various conditions. Both processes fitted the pseudo-first-order kinetic model and the reaction rate constant of the O-3/SPC process under low SPC dosage (30 mg L-1) was more than two times higher than for O-3 alone. The DDVP removal performance was evaluated in terms of initial pH, O-3 dosage, SPC dosage and water matrix. The pH played a significant role in DDVP degradation during the O-3/SPC process, especially on the occurrence of the different types of reactive species. Based on radical scavenger experiments, OH- were observed over the full pH range but dominated under neutral and alkaline conditions, while less oxidative CO3 center dot- emerged at lower pH. Furthermore, the complex matrix of real wastewater inhibited the oxidation process due to the competition for oxidative species between organic matter and DDVP. A modified kinetic model based on a steady-state hypothesis was established to predict DDVP degradation via the O-3/SPC treatment and provided a fair result under different conditions. This observation suggested that eco-friendly SPC could be considered as a promising alternative for H2O2 in developing sustainable ozone-based oxidation processes for recalcitrant compounds elimination in wastewater treatment.

Automated summary

In this study, a combination of SPC and ozone was found to be more efficient in degrading DDVP compared to ozone alone, providing a promising alternative for the elimination of recalcitrant compounds in wastewater treatment. The presence of reactive species such as OH- and CO3 center dot- was crucial in enhancing the degradation process, with pH playing a significant role in the generation of these species. This environmentally friendly approach could potentially improve the sustainability of ozone-based oxidation processes.