The promotions on radical formation and micropollutant degradation by the synergies between ozone and chemical reagents (synergistic ozonation): A review

Abstract The combination of ozone (O3) and chemical reagents (such as H2O2) shows synergies on the radical formation and micropollutant degradation. The promoting performance was associated with various parameters including chemical reagents, micropollutants, solution pH, and the water matrix. In this review, we summarized existing knowledge on radical formation pathways, radical yields, and radical oxidation for different synergistic ozonation processes in various water matrices (such as groundwater, surface water, and wastewater). The increase of radical yields by synergistic ozonation processes was positively related to the increase of O3-decay, with the increase being 1.1–4.4 folds than ozonation alone (0.2). Thus, synergistic ozonation can promote the degradation rate and efficiency of O3-resistant micropollutants (second order rate constant, kP,O3 200 M−1 s−1). The water matrices, such as the dissolved organic matters, negatively suppressed the degradation of micropollutant by quenching O3-oxidation and radical oxidation (i.e. maximum promoting was decreased by 1.3 times), but may positively extend the promoting effects of synergistic ozonation to micropollutants that are more reactive to O3 (i.e. kP,O3 was extended from