TY - JOUR
T1 - Electrochemical oxidation of benzoic acid and its aromatic intermediates on boron doped diamond electrodes
AU - Arts, Anke
AU - van den Berg, Kevin P.
AU - de Groot, Matheus T.
AU - van der Schaaf, John
N1 - Funding Information:
This work was performed as part of the HIGHSINC program, a collaboration between Nouryon and Eindhoven University of Technology.
PY - 2021/1
Y1 - 2021/1
N2 - Electrochemical oxidation using Boron-doped diamond (BDD) electrodes is a promising purification technique to remove organic pollutants, such as benzoic acid, from wastewaters. In this study the oxidation of benzoic acid has been investigated on rotating disk electrodes and in flow cells with well-defined mass transfer. The oxidation of benzoic acid on BDD proceeds via the formation of 4-hydroxybenzoic acid, which reacts in consecutive steps towards hydroquinone and benzoquinone. The ring opening in the oxidation of benzoquinone results in the formation of aliphatic carboxylic acids. It was shown that the intermediates 4-hydroxybenzoic acid and hydroquinone can be oxidized prior to water oxidation, which suggests the reaction occurs via a DET mechanism. Benzoquinone is not oxidized before water oxidation and can presumably solely be oxidized by [rad]OH radicals. This means that in order to oxidize benzoic acid completely to CO2 the formation of [rad]OH radicals is needed. Finally, the effects of mass transfer were analyzed. It was shown that the conversion rates of benzoic acid, benzoquinone and 4-hydroxybenzoic acid were below the limiting mass transfer rates, implying that these reactions are primarily limited by kinetics.
AB - Electrochemical oxidation using Boron-doped diamond (BDD) electrodes is a promising purification technique to remove organic pollutants, such as benzoic acid, from wastewaters. In this study the oxidation of benzoic acid has been investigated on rotating disk electrodes and in flow cells with well-defined mass transfer. The oxidation of benzoic acid on BDD proceeds via the formation of 4-hydroxybenzoic acid, which reacts in consecutive steps towards hydroquinone and benzoquinone. The ring opening in the oxidation of benzoquinone results in the formation of aliphatic carboxylic acids. It was shown that the intermediates 4-hydroxybenzoic acid and hydroquinone can be oxidized prior to water oxidation, which suggests the reaction occurs via a DET mechanism. Benzoquinone is not oxidized before water oxidation and can presumably solely be oxidized by [rad]OH radicals. This means that in order to oxidize benzoic acid completely to CO2 the formation of [rad]OH radicals is needed. Finally, the effects of mass transfer were analyzed. It was shown that the conversion rates of benzoic acid, benzoquinone and 4-hydroxybenzoic acid were below the limiting mass transfer rates, implying that these reactions are primarily limited by kinetics.
KW - Benzoic acid
KW - Boron doped diamond
KW - Electrooxidation
KW - Flow cell
KW - Mass transfer
KW - Rotating disk
UR - https://www.scopus.com/pages/publications/85119344337
U2 - 10.1016/j.crgsc.2021.100217
DO - 10.1016/j.crgsc.2021.100217
M3 - Article
AN - SCOPUS:85119344337
SN - 2666-0865
VL - 4
JO - Current Research in Green and Sustainable Chemistry
JF - Current Research in Green and Sustainable Chemistry
M1 - 100217
ER -