Degradation of the chlorophenoxyacetic herbicide 2,4-D by plasma-ozonation system

•Novel AOP based on the combination of ozonation with non-thermal plasma.•Improved degradation and mineralization of 2,4-D by O3+plasma as compared to O3.•Two times faster 2,4-D removal by O3+plasma than by ozonation.•Almost complete mineralization of 2,4-D after 60min O3+plasma treatment.•Enhanced energy efficiency obtained by reducing discharge pulse duration. A novel advanced oxidation process based on the combination of ozonation with non-thermal plasma generated in a pulsed corona discharge was developed for the oxidative degradation of recalcitrant organic pollutants in water. The pulsed corona discharge in contact with liquid, operated in oxygen, produced 3.5mgL−1 ozone, which was subsequently introduced in the ozonation reactor. The solution to be treated was continuously circulated between the plasma reactor and the ozonation reactor. The system was tested for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and considerably improved performance as compared to ozonation alone, both with respect to the removal of the target compound and to mineralization. The apparent reaction rate constant for 2,4-D removal was 0.195min−1, more than two times higher than the value obtained in ozonation experiments. The mineralization reached more than 90% after 60min treatment and the chlorine balance confirms the absence of quantifiable amounts of chlorinated by-products. The energy efficiency was considerably enhanced by shortening the duration of the discharge pulses, which opens the way for further optimization of the electrical circuit design.