Insights into ultrasound-promoted degradation of naphthenic acid compounds in oil sands process affected water. Part I: Accelerated H-abstraction and decarboxylation of aromatic and alicyclic compounds

Abstract

Graphical abstract

Insights into ultrasound-promoted degradation of naphthenic acid compounds in oil sands process affected water. Part II: In silico quantum screening of hydroxyl radical initiated and propagated degradation of benzoic acid

“…These modifications presented in Part 1 of this study were confirmed by the Fukui calculations and an additional NEB-TS calculation of benzoic acid to phenol by OH radical attacks yielded 3hBA as a transition state [5] . The Fukui coefficients of 3-hydroxybenzoic acid suggested 3, 4-dihydroxybenzoic acid as the product rather than the suggested 2, 3-dihydroxybenzoic acid.…”

“…A reaction shift towards OH • radicals may be enhanced by the introduction of ozone or similar oxidants into the process. It was reported and confirmed [5] that during sonication, model organic acids such as benzoic acid, due to their volatile and hydrophobic nature, diffuse to the cavitation bubble and decompose by pyrolysis and/or OH • degradation by a range of steps as shown in Fig. 1 .…”

“…Ten NEB images were used to create a detailed reaction profile. Based on the empirical identification of degradation compounds from Part I [5] , a suggested transition state was applied in ring-opening reaction steps to facilitate the reaction progress within NEB-TS and avoid radical attacks expected due to the limitations of the NEB-TS approach. Avogadro auto optimization was used to obtain the suggested transition states of the targeted reaction by selecting an arbitrary step immediately following radical attack.…”

“…This study explores the QM screening strategy through the known degradation pathway of benzoic acid and its intermediates via a theoretical approach using DFT studies to complete mineralization from previous works and our previous study [5] . Geometry optimizations, frequency calculations, transitions states, interaction energies, Mulliken charges, Hirshfeld population analysis, dipole moments, and polarizabilities have all been calculated by DFT method.…”

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Fig. 1 Initial sonochemical degradation mechanism for BA through H-abstraction and decarboxylation reactions [2] , [5] .

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