Oxidized activated carbon as support for titanium dioxide in UV-assisted degradation of 3-chlorophenol

Strong adsorption of pollutants on activated carbon may inhibit their diffusion to the catalyst on the surface of the adsorbent and hence reduce the whole photocatalytic process. Oxidation of the carbon surface will change the adsorption properties of the carbon; and increase the capability of carbon surface to carry more titanium dioxide. In this work, activated carbon was oxidized with different oxidizing agents (nitric acid, ammonium persulfate, and hydrogen peroxide) to produce carbons with different surface chemistries. Titanium dioxide was deposited on oxidized and non-oxidized carbons, in which titanium dioxide loading was higher in the oxidized carbons. The produced materials were tested in UV-assisted mineralization of 3-chlorophenol in aqueous medium. Results showed that 1 g of the product made by deposition of titanium dioxide on hydrogen peroxide-oxidized carbon (23.5% titanium dioxide) caused photo-mineralization of 40% of the 3-chlorophenol within 5 h; while half gram of titanium dioxide (pure anatase) caused photo-mineralization of 58% of 3-chlorophenol within the same period. It seems that 3-chlorophenol decomposed entirely with titanium dioxide deposited on other oxidized and non-oxidized carbons, but complete mineralization into chloride, CO2 and H2O was not achieved. A mixture of titanium dioxide (anatase) and non-oxidized carbon showed that mineralization is taking place even when all 3-chlorophenol was adsorbed on carbon surface. This suggests that adsorbed 3-chlorophenol is involved in the mineralization process. (C) 2006 Elsevier B.V. All rights reserved.