Direct Determination of Absolute Radical Quantum Yields in Hydroxyl and Sulfate Radical-Based Treatment Processes.
Environ Sci Technol
; 58(20): 8966-8975, 2024 May 21.
Article
em En
| MEDLINE
| ID: mdl-38722667
ABSTRACT
The absolute radical quantum yield (Φ) is a critical parameter to evaluate the efficiency of radical-based processes in engineered water treatment. However, measuring Φ is fraught with challenges, as current quantification methods lack selectivity, specificity, and anti-interference capabilities, resulting in significant error propagation. Herein, we report a direct and reliable time-resolved technique to determine Φ at pH 7.0 for commonly used radical precursors in advanced oxidation processes. For H2O2 and peroxydisulfate (PDS), the values of Φâ¢OH and ΦSO4â¢- at 266 nm were measured to be 1.10 ± 0.01 and 1.46 ± 0.05, respectively. For peroxymonosulfate (PMS), we developed a new approach to determine Φâ¢OHPMS with terephthalic acid as a trap-and-trigger probe in the nonsteady state system. For the first time, the Φâ¢OHPMS value was measured to be 0.56 by the direct method, which is stoichiometrically equal to ΦSO4â¢-PMS (0.57 ± 0.02). Additionally, radical formation mechanisms were elucidated by density functional theory (DFT) calculations. The theoretical results showed that the highest occupied molecular orbitals of the radical precursors are O-O antibonding orbitals, facilitating the destabilization of the peroxy bond for radical formation. Electronic structures of these precursors were compared, aiming to rationalize the tendency of the Φ values we observed. Overall, this time-resolved technique with specific probes can be used as a reliable tool to determine Φ, serving as a scientific basis for the accurate performance evaluation of diverse radical-based treatment processes.
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Base de dados:
MEDLINE
Assunto principal:
Sulfatos
/
Radical Hidroxila
Idioma:
En
Ano de publicação:
2024
Tipo de documento:
Article