Regular Article

Experimental and theoretical study on chemical reactions and species diffusion by a nano-pulse discharged bubble for water treatment

¹ Graduate School of Engineering, Tohoku University, 6-6-01, Aza-Aoba Aramaki, Aoba, Sendai, Miyagi 980-8579, Japan
² Institute of Fluid Science, Tohoku University, 2-1-1, Katahira, Aoba, Sendai, Miyagi 980-8577, Japan

^a e-mail: he@paris.ifs.tohoku.ac.jp

Received: 6 April 2017
Received in final form: 14 September 2017
Published online: 18 January 2018

Abstract

Advanced oxidation processes using hydroxyl radicals (⋅OH) generated inside bubbles in water has drawn widely interest for the high oxidation potential of OH radical to decompose persistent organic pollutants such as dioxins and humic acid for water purification. In this study, a two-dimensional diffusion model for a nano-pulse discharged bubble in water is established. Based on the experimental results of streamer propagation inside a bubble, the diffusion processes around the bubble interface and reactions of chemical species in liquids are simulated. The simulation results show that OH radicals can diffuse only several micrometers away from the bubble interface in water. Furthermore, the optimal operating voltage and frequency conditions for OH generation is obtained by comparing the OH concentration in water obtained from numerical simulation with that measured by spectroscopy in experiment.