Oxidation and mineralization rates of harmful organic chemicals in hydroxyl radical induced reactions

• Published in: Ecotoxicology and environmental safety Vol. 281; p. 116669
• Main Authors: Wojnárovits, László, Homlok, Renáta, Kovács, Krisztina, Tegze, Anna, Takács, Erzsébet
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.08.2024; Elsevier
• Subjects: Chemical oxygen demand; Hydroxyl radical; Mineralization rate; Oxidation rate; Total organic carbon; AOP; AOS; Chemical oxygen demand; Mineralization rate; COD; TOC; Total organic carbon; Oxidation rate; Hydroxyl radical
• ISSN: 0147-6513; 1090-2414; 1090-2414
• DOI: 10.1016/j.ecoenv.2024.116669

In most of advanced oxidation processes (AOPs) used to destroy harmful organic chemicals in water/wastewater hydroxyl radical (•OH) reactions oxidize (increasing the oxygen/carbon ratio in the molecules) and mineralize (transforming them to inorganic molecules, H2O, CO2, etc.) these contaminants. In this paper, we used the radiolysis of water to produce •OH and characterised the rate of oxidation and mineralization by the dose dependences of the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) content values. Analysis of the dose dependences for 34 harmful organic compounds showed large differences in the oxidation and mineralization rates and these parameters are characteristic to the given group of chemicals. E.g., the rate of oxidation is relatively low for fluoroquinolone antibiotics; it is high for β-blocker medicines. Mineralization rates are low for both fluoroquinolones and β-blockers. The one-electron-oxidant •OH in most cases induces two − four-electron-oxidations. Most of the degradation takes place gradually, through several stable molecule intermediates. However, based on the results it is likely, that some part of the oxidation and mineralization takes place parallel. The organic radicals formed in •OH reactions react with several O2 molecules and release several inorganic fragments during the radical life cycle. [Display omitted] •Slopes of COD and TOC vs. dose characterize rate of oxidation and mineralization.•Slopes allow calculation of oxidation number induced by one-electron-oxidant •OH.•Slope values are characteristics to the groups of chemicals with similar structure.•In fluoroquinolones on average •OH induces two-electron-oxidations.•This number for β-blockers and macrolides is four.