Advanced oxidation effect of ozonation combined with electrolysis

The advanced oxidation effect of ozonation combined with electrolysis (electrolysis–ozonation) was discussed through the treatment of 4-chlorobenzoic acid (4-CBA) as a hydroxyl radical probe. The mechanism of hydroxyl radical production by electrolysis–ozonation process was also estimated with a mathematical model. The experimental results revealed that the electrolysis–ozonation process had a synergistic effect on the degradation of 4-CBA. The advanced oxidation effect of electrolysis–ozonation was inferred from standard potentials of relevant electrochemical reactions and mathematical model analysis to be mainly attributed to O3− promotion of O3 at the cathodes. An increase in electric current improved the degradation rate of 4-CBA. However, the pseudo-first order degradation rate constant reached a plateau at high electric current densities, as O3− promotion of O3 at the cathodes was regulated by O3 transport process from the bulk to the cathodes in the range exceeding an electric current density of 10 A m−2. Accordingly, the balance of O3 transport flux and electric current is important for the efficient operation of the electrolysis–ozonation reactor.