Caveats in the Use of Tertiary Butyl Alcohol as a Probe for Hydroxyl Radical Involvement in Conventional Ozonation and Catalytic Ozonation Processes

Abstract

In this study, we enunciate the limitations associated with the use of tert-butanol (TBA) to deduce the contribution of hydroxyl radicals ( • OH) in organic oxidation during conventional ozonation and/or heterogeneous catalytic ozonation (HCO). Our results show that TBA is unable to access surface-located • OH formed during HCO. Furthermore, TBA may also interfere with the adsorption of organic compounds on the catalyst surface and decrease the adsorptive as well as concomitant oxidative removal of organics via nonradical-mediated pathways (if important). Our results also demonstrate that TBA scavenging results are inconclusive for mildly ozone reactive compounds due to switching from O 3 / • OH-mediated oxidation in the absence of TBA to O 3 -driven oxidation in the presence of TBA. The presence of TBA may also decrease the rate of ozone decay with the increased stability of O 3 in the presence of TBA, facilitating (i) direct oxidation of ozone-reactive organics in the bulk solution and/or (ii) diffusion of O 3 to the catalyst surface and subsequent surface-mediated oxidation of organics. Overall, we conclude that caution needs to be exercised when interpreting the observations made in the presence of TBA and also describe the further experimentation required to confirm/reject the role of • OH in organic oxidation. The findings of this work should assist in preventing researchers from reaching erroneous conclusions regarding the involvement of • OH in catalytic or conventional ozonation processes.

Kinetic Modeling-Assisted Optimization of the Peroxone (O3/H2O2) Water Treatment Process

“…As a result, O 3 decay and associated generation of • OH in the presence of TBA occur via the H 2 O 2 –O 3 reaction. As reported in various earlier studies, − the influence of TBA and its intermediate products on O 3 decay and associated • OH generation is minimal.…”

Dimethyl Sulfoxide: An Ideal Electrochemical Probe for Hydroxyl Radical Detection

“…The electrochemically active substance (MSIA) produced by the reaction of DMSO with • OH is the key component to achieve quantification. Similar to DMSO, IPA and TBA are also electrochemically inert in the potential windows applied and they were used as • OH scavengers with reaction rates of 6 × 10 9 and 5 × 10 8 M –1 s –1 , respectively. − However, no electrochemically active substances are produced by their reaction with • OH, so these compounds cannot be used for the determination of • OH (Figure S2). Although IPA and TBA could also react with • OH, DMSO exhibits a higher affinity for • OH.…”

Tailored Metal–Organic Frameworks for Water Purification: Perfluorinated Fe–MOFs for Enhanced Heterogeneous Catalytic Ozonation

“… The contribution of sorption to C 2 O 4 2– removal was determined based on the difference between the total C 2 O 4 2– removal and CO 2 production (see Section S1 for the method used for measurement of CO 2 production). TBA was employed as a bulk • OH scavenger to probe the contribution of bulk • OH to the oxidation of C 2 O 4 2– by HCO. , …”