Quantification of OH radicals generated by nanosecond pulsed discharge plasma

In conventional water treatment, wastewater is purified by a biological method. However, this method has some problems, such as dissipation of time, high cost for treatment, necessity of large facilities, and existence of some pollutants that are not easily to be decomposed. Therefore, the development of advanced water treatment technologies that can solve those problems is required. In recent years, discharge plasmas have been used as effective method for purifying environmentally polluted water. Some researchers reported that the species which have high oxidation potential, such as OH radical, O radical, O₃ and etc., are produced by pulsed discharge plasmas generated in water surface. Among them, OH radicals have the highest oxidizing power. In this work, OH radicals generated by the nanosecond pulsed discharge was evaluated using a chemical prove method. In this method, terephthalic acid (TA) was used as an OH radical scavenger and the given fluorescence of the resulted 2-hydroxyterephthalic acid (HTA) was measured. However, it can be estimated that the HTA in the reaction process could be decomposed by discharge afterwards. Furthermore, there is no report of OH radical measurement based on the amount of HTA decomposition. This means, the accuracy of OH radical evaluation needs room to improve. Therefore, we measured the amount of HTA decomposition by nanosecond pulsed discharge, and successfully examined the decomposition amount of HTA. As the result, the generated OH radicals with consideration of HTA decomposition is successfully evaluated.