Mechanistic insights for the electro-Fenton regeneration of carbon materials saturated with methyl orange: Dominance of electrodesorption

Abstract

Adsorption followed by regeneration of the adsorbent is a sustainable way to remove pollutants from water systems. In this study, the electro-Fenton regeneration of activated carbon and mesoporous carbon loaded with magnetic γ-Fe₂O₃ and then saturated with an anionic adsorbate, methyl orange, has been studied. The saturated adsorbents were regenerated and the influence of several factors on the regeneration efficiency and pore structure recovery was systematically investigated. Regeneration was improved with a higher cathodic potential, better contact with the cathode, and larger pores. The addition of an electrochemical potential improved the regeneration of adsorption sites within micropores. A mathematical model based on electrostatic, solvation, and dispersion interaction energies was developed to explain the regeneration process. Cationic (methylene blue) and neutral (benzoic acid) adsorbates were also tested to further test the model predictions. Overall, the results support electro-desorption being the dominant pathway during electro-Fenton regeneration of the carbon materials, with cathodic reduction and electro-Fenton oxidation contributing a minor part to the regeneration via degradation of the desorbed methyl orange.

Keywords: Adsorption; Carbon; Electro-Fenton; Electro-desorption; Regeneration.