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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 3.5 mg L −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 0.195 min −1 , more than two times higher than the value obtained in ozonation experiments. The mineralization reached more than 90% after 60 min 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. [ABSTRACT FROM AUTHOR]

Highlights: [•] Efficient removal of diclofenac in water was obtained by pulsed corona discharge. [•] Diclofenac in solution was completely removed after 15min plasma treatment. [•] Total Organic Carbon (TOC) decreased by 50% after 30min exposure to plasma. [•] No chlorinated degradation products are present at the end of plasma treatment. [•] Short-chain carboxylic acids were detected as by-products in the treated solution. [ABSTRACT FROM AUTHOR]

A pulsed corona discharge above liquid combined with ozonation has been investigated for the degradation of organic pollutants in water, as well as regarding the generation of several oxidizing species: ozone in gas phase, hydrogen peroxide and hydroxyl radicals in the liquid. A considerable improvement in the energy efficiency for organic compounds removal has been observed when reducing the width of the discharge pulses. This finding was correlated with the efficient formation of oxidizing species in case of short pulses. Recycling of the effluent gas from the plasma also enhances contaminants degradation. This was mainly attributed to an in situ peroxone process, i.e. the reaction between plasma-generated O 3 and H 2 O 2 , forming highly reactive OH radicals, largely responsible for organic compounds degradation. This assumption is supported by the decline in O 3 and H 2 O 2 concentrations and simultaneous increase in OH concentration detected in plasma-ozonation experiments as compared to results obtained with plasma alone. • The formation of O 3 , H 2 O 2 ,. OH was investigated in a corona discharge above liquid. • Pollutants removal efficiency can be enhanced by reducing discharge pulse width. • Formation of oxidizers in plasma is favoured for short pulse durations. • Efficiency of plasma treatment of water can be improved by plasma gas recycling. • In-situ peroxone process is essential in plasma-ozonation configuration. [ABSTRACT FROM AUTHOR]