New insights into the influence of activated carbon surface oxygen groups on H2O2 decomposition and oxidation of pre-adsorbed volatile organic compounds

Abstract

In this study, the influence of the surface oxygen groups of activated carbons (ACs) on the decomposition of H2O2 and the consequent OH radicals generation is investigated. The oxidation of pre-adsorbed volatile organic compounds by H2O2 is also studied. Four ACs, with low percentage of inorganic matter (<0.2%), similar textural properties but differing in their surface oxygen content were evaluated. The surface oxygen groups of the ACs were characterised by using appropriate characterisation techniques (temperature programmed desorption and X-ray photoelectron spectroscopy). The kinetic curves of H2O2 decomposition were very similar for all the ACs. However, different profiles in the production of OH radicals were observed. OH radicals generation seemed to be promoted by low surface oxygen contents. Oxidation of two volatile organic compounds (VOCs) of different polarity, methyl ethyl ketone (MEK) and toluene, pre-adsorbed onto the ACs was finally investigated. H2O2 was used as oxidising agent. Both VOCs presented similar maximum oxidation rates, around 70%, in spite of their different hydrophobicity. Some evidences are provided supporting that oxidation of pre-adsorbed VOCs can take place in the inner pore structure of the ACs