Generation of hydroxyl radical on water treatment using nanosecond pulsed powers and its effect

Recently, water pollution is one of environment issues around the world. We have studied a water treatment using nanosecond pulsed powers. The water treatment utilizes not only active species such as hydroxyl radical produced by electric discharges but also direct actions of discharges such as ultraviolet rays, shock wave and so on. In treatment for surfactant solution using pulsed power system, purified water and tap water was used as solvents of the solution. As a result, when purified water was used as solvent of solution, foaming which is a typical property of surfactants disappeared faster than in the case of using tap water as solvent. To investigate reasons of this result, disodium terephthalate was added to the solution. Disodium terephthalate was used to evaluate production of hydroxyl radical. Disodium terephthalate in purified water would react with more hydroxyl radical than in tap water. When an external ozonizer was used for water treatment instead of pulsed power system, production of hydroxyl radical in purified water was as much as in tap water. This is considered that more hydroxyl radical was generated by electric discharge in purified water because the conductivity of purified water was lower than that of tap water. On the other hand, in case of using external ozonizer without electric discharge, water treatment was unaffected by the conductivity of solution. Consequently, it seemed that electric discharges and lower conductivity of solution contributed treatment of organic compounds such as surfactant.