Experimental and theoretical insight into hydroxyl and sulfate radicals-mediated degradation of carbamazepine
| Autor: | Ruiyang Xiao, Zonghao Luo, Zongsu Wei, Wei-Ping Hu, Weizhi Zeng, Junye Ma, Dionysios D. Dionysiou, Richard Spinney |
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| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Reaction mechanism
010504 meteorology & atmospheric sciences Health Toxicology and Mutagenesis Kinetics Wastewater treatment Wastewater 010501 environmental sciences Toxicology 01 natural sciences DFT chemistry.chemical_compound Reaction rate constant Computational chemistry Molecule 0105 earth and related environmental sciences Sewage Hydroxyl Radical Sulfates Advanced oxidation processes General Medicine Biodegradation Pollution Carbamazepine chemistry Sulfate radical Thermodynamics Degradation (geology) Density functional theory Hydroxyl radical Oxidation-Reduction Water Pollutants Chemical |
| Zdroj: | Xiao, R, Ma, J, Luo, Z, Zeng, W, Wei, Z, Spinney, R, Hu, WP P & Dionysiou, D D 2020, ' Experimental and theoretical insight into hydroxyl and sulfate radicals-mediated degradation of carbamazepine ', Environmental Pollution, vol. 257, 113498 . https://doi.org/10.1016/j.envpol.2019.113498 |
| DOI: | 10.1016/j.envpol.2019.113498 |
| Popis: | Carbamazepine (CBZ), a widely detected pharmaceutical in wastewaters, cannot currently be treated by conventional activated sludge technologies, as it is highly resistant to biodegradation. In this study, the degradation kinetics and reaction mechanisms of CBZ by hydroxyl radical ([rad]OH) and sulfate radical ([Formula presented])–based advanced oxidation processes (AOPs) were investigated with a combined experimental/theoretical approach. We first measured the UV absorption spectrum of CBZ and compared it to the theoretical spectrum. The agreement of two spectra reveals an extended π–conjugation system on CBZ molecular structure. The second–order rate constants of [rad]OH and [Formula presented] with CBZ, measured by competition kinetics method, were (4.63 ± 0.01) × 109 M−1 s−1 and (8.27 ± 0.01) × 108 M−1 s−1, respectively at pH 3. The energetics of the initial steps of CBZ reaction with [rad]OH and [Formula presented] were also calculated by density functional theory (DFT) at SMD/M05–2X/6–311++G**//M05–2X/6–31 + G**level. Our results reveal that radical addition is the dominant pathway for both [rad]OH and [Formula presented]. Further, compared to the positive ΔGR0 value for the single electron transfer (SET) reaction pathway between CBZ and [rad]OH, the ΔGR0 value for SET reaction between CBZ and [Formula presented] is negative, showing that this reaction route is thermodynamically favorable. Our results demonstrated the remarkable advantages of AOPs for the removal of refractory organic contaminants during wastewater treatment processes. The elucidation of the pathways for the reaction of [rad]OH and [Formula presented] with CBZ are beneficial to predict byproducts formation and assess associated ecotoxicity, providing an evaluation mean for the feasibility of AOPs application. The k values of [rad]OH and [Formula presented] reacting with CBZ were measured to be 4.63 × 109 and 8.27 × 108 M−1 s−1, respectively. Radical addition is dominant reaction pathway. |
| Databáze: | OpenAIRE |
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