Electrochemical degradation of vanillin using lead dioxide electrode: influencing factors and reaction pathways

ABSTRACT

In this study, a novel PbO₂-CeO₂ composite electrode was applied it to the electrocatalytic degradation of vanillin. The operating parameters such as applied current density, initial vanillin concentration, supporting electrolyte concentration and pH value were investigated and optimised. After 120 min, in a 0.10 mol L⁻¹ Na₂SO₄ solution with a current density of 50 mA cm⁻² and a pH value of 5.0 containing 30 mg L⁻¹ vanillin, the vanillin removal efficiency can reach 98.03%, the COD removal efficiency is up to 73.28%. The results indicate that electrochemical degradation has a high ability to remove vanillin in aqueous solution. The reaction follows a pseudo-first-order reaction kinetics model with rate constants of 0.03036 min⁻¹. In the process of electrochemical degradation, up to eight hydroxylated or polyhydroxylated oxidation by-products were identified through hydroxylation, dealkylation and substitution reactions. Furthermore, the degradation pathways were proposed, which eventually mineralised into inorganic water and carbon dioxide.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electrochemical degradation
• vanillin
• PbO₂ electrodes
• intermediates
• reaction pathway

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (No. 21576065, 21402038) and the Natural Science Foundation of Hebei Province of China (B2015202289, B2019202003, B2020202016).