Photochemical behaviour of activated carbons under UV irradiation

A series of activated carbons were used to investigate the photochemical behaviour of carbons under UV light as catalysts in the photo-oxidation of phenol in the absence of semiconductor additives. Conventional photocatalytic tests showed an improved photo-oxidation in the presence of activated carbons, beyond the so-called synergistic effect reported in the literature for carbon/titania composites. A novel approach based on UV irradiation of carbons pre-loaded with phenol was used to demonstrate the anomalous photochemical response of carbon materials towards phenol degradation. Analysis of the catalytic reaction from a different standpoint (inside the carbonaceous matrix) demonstrated the catalytic activity of certain carbon materials for phenol photodegradation, without considering photolytic breakdown and adsorption kinetics. The pseudo photochemical quantum yield of several activated carbons was higher than that of photolysis under the same conditions; the nature of the degradation intermediates was also modified in the presence of the carbon materials. Moreover, the degradation of the adsorbed fraction retained inside the pore structure of the carbons has been demonstrated. Our results suggest the occurrence of carbon–photon interactions which could be propagated through the graphene sheets of the materials, and could reach the adsorbed molecules inside the pores.