Highly efficient application of activated carbon as catalyst for wet peroxide oxidation

Abstract

This paper addresses the improved performance of activated carbons in catalytic wet peroxide oxidation (CWPO) of phenol as target compound. Initial cyclic voltammetry experiments show that hydrogen peroxide and phenol compete for the same active sites on the carbon surface. Then, a significant coverage of the carbon surface by phenol molecules is the approach attempted to increase the efficiency of hydrogen peroxide and the performance of the oxidation process.In this work, two commercial activated carbons, with different physical and electrochemical properties have been tested. The results demonstrate that working at high phenol concentration (5g/L) and phenol/carbon mass ratio (2), unprecedented hydrogen peroxide efficiencies of around 100% are achieved, allowing high oxidation and mineralization degrees, i.e. 97% phenol and 70% TOC conversions at 80°C with the stoichiometric dose of hydrogen peroxide required for complete mineralization of phenol. The oxidation route of phenol in the presence of activated carbon is also studied and a reaction pathway proposed. Resorcinol was a new by-product detected whose formation occurs upon reaction on the carbon surface. Condensation by-products, typically formed in Fenton oxidation of phenol, were not found in the effluents but adsorbed on the carbon surface causing a progressive deactivation upon use. The activity can be easily recovered by oxidative thermal regeneration (350°C, 24h).