Uncertainty and misinterpretation over identification, quantification and transformation of reactive species generated in catalytic oxidation processes: A review

• Published in: Journal of hazardous materials Vol. 408; p. 124436
• Main Authors: Wang, Lingli, Lan, Xu, Peng, Wenya, Wang, Zhaohui
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.04.2021
• Subjects: catalysts; electron paramagnetic resonance spectroscopy; EPR; oxidation; Probe; Quenching test; Radicals; Transformation; uncertainty; Quenching test; Transformation; Probe; EPR; Radicals
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2020.124436

The identification of reactive radical species using quenching and electron paramagnetic resonance (EPR) tests has attracted extensive attention, but some mistakes or misinterpretations are often present in recent literature. This review aims to clarify the corresponding issues through surveying literature, including the uncertainty about the identity of radicals in the bulk solution or adsorbed on the catalyst surface in quenching tests, selection of proper scavengers, data explanation for incomplete inhibition, the inconsistent results between quenching and EPR tests (e.g., SO4•− is predominant in quenching test while the signal of •OH predominates in EPR test), and the incorrect identification of EPR signals (e.g., SO4•− is identified by indiscernible or incorrect signals). In addition, this review outlines the transformation of radicals for better tracing the origin of radicals. It is anticipated that this review can help in avoiding mistakes while investigating catalytic oxidative mechanism with quenching and EPR tests. [Display omitted] •The determination methods for detecting reactive radical species are summarized.•The uncertainty about the identity of radicals in quenching tests is proposed.•The misinterpretations over the radical identification in EPR tests are reviewed.•The transformation and interconversion of radicals are concluded.