Ozonation is a process widely applied in drinking or wastewater treatment where it can be used as a cost-effective disinfectant or for micropollutant removals. Additionally to these uses, ozone reacts with dissolved organic matter (DOM) present in the water matrix affecting both DOM optical properties and the generation potential of reactive intermediates such as singlet oxygen (1O2) and hydroxyl radicals (●OH). Our experiments show that ozonation induced a large decrease (factor ≤ 50) in the absorption properties of DOM while an important increase in 1O2 and ●OH quantum yields (Φ1O2 and Φ●OH respectively) was observed (factor ≤ 8 and 28 respectively). The decrease was attributed to the preferential reaction of ozone with the phenolic and aromatic moieties of DOM while the increase in Φ1O2 to the production of quinone moieties from the ozonation of phenolic compounds. Several pathways that lead to the formation of ●OH from DOM irradiation were proposed. They include H2O2 dependent pathways such as the Fenton reaction and H2O2 independent pathways that include the irradiation of hydroxy-substituted benzoic acid and the oxidation of water or hydroxyl by 3DOM*. The observed increase in Φ●OH upon ozonation indicates that the later process is more plausible as ozonation of DOM should lead to the disappearance of hydroxy-substituted benzoic acids and to the formation of quinones that have high triplet quantum yield under photo-irradiation. This study is a step forward in understanding the effects of ozone on DOM and hope to give some insights in DOM photochemistry.

Effects of ozonation on the dissolved organic matter and the photoproduction of reactive intermediates

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.