Description
Recently, improvements of drainage water treatment technology has been required. The streamer discharges generated by nanosecond pulsed power was applied to treat surfactant solution as a persistent chemical. Radicals with a high redox potential, such as especially hydroxyl radical, is expected for degradative treatment of the persistent chemical. The effects on production of hydroxyl radical and the treatment of the surfactant solution was studied, by changing the ozone concentration in the treatment reactor when oxygen gas was used as a surrounding gas. The treatment experiment of anionic surfactant was carried out with a coaxial cylindrical reactor by changing the flow rate of oxygen gas. The voltage pulses of 1.5-ns pulse-width were applied on a solution of 1 L of purified water dissolved with 0.1 g of sodium dodecyl benzene sulfonate (DBS) as an anionic surfactant for 80 minutes. The concentration of anionic surfactant was evaluated with a methylene blue visual colorimetric method. The concentration of the surfactant decreased with treatment time. The absorbance at 225 nm, where was a peak absorbance of DBS, decreased with treatment time, and then, treatment of the anionic surfactant was confirmed with the two methods. On the other hand, the absorbance at 260 nm of the solution increased with treatment time. Because ozone in water had a peak absorbance at 260 nm, it implied that ozone was dissolved in the solution and hydroxyl radical was produced as a result. The ozone concentration ejected from the treatment reactor decreased with increase of flow rate of oxygen gas. On the other hand, treatment speed of surfactant was not significantly changed with the flow rate. The electrical conductivity significantly increased from 26.3 μS/cm to 126.1 μS/cm in the treatment. The change in conductivity might affect the generation of streamer discharges on the solution surface.
