Influence of Water Vapor on the Adsorption of VOCs on Lignin-Based Activated Carbons Jose ´ Rodrı ´guez-Mirasol, Jorge Bedia, and Toma ´s Cordero Chemical Engineering Department, School of Industrial Engineering, University of Ma ´laga, Ma ´laga, Spain Juan J. Rodrı ´guez Chemical Engineering, University Auto ´noma of Madrid, Madrid, Spain Abstract: Activated carbons with a wide range of burn-off degrees obtained from Euca- lyptus kraft lignin have been used to study the influence of the presence of water vapor on VOCs adsorption. The amount adsorbed and the rate of adsorption of both benzene and water vapor increase with activated carbon burn-off as a consequence of an increase of micropore volume, broadening of micropore size distribution and increasing development of meso- and macroporosity. Similar results were found for MEK and methanol. Benzene is only partially desorbed at the adsorption temperature and an appreciable amount of it remains in the carbon, most likely in the narrow micropores. On the contrary, water vapor is completely desorbed at the adsorption temperature and its adsorption profile clearly exhibits two steps with different adsorption rates, associated to water molecules adsorbed on the active sites given rise to cluster formation and further migration and filling of the micropores. Adsorption with mixtures of VOC and water vapor has been carried out. The total amount adsorbed by the carbon, near the equilibrium point, is higher than in the case of the stream containing only the VOC. The adsorption rates for the mixtures streams are similar to that for the corresponding streams containing only the VOC in the case of carbons with a well developed porous structure. However, the presence of water vapor increases the rate of adsorption on the activated carbons with narrower microporosity. Saturation of the activated carbon with water vapor prior to the adsorption of a mixture containing benzene and water vapor has shown little effect Received 6 February 2005, Accepted 2 September 2005 Address correspondence to Jose ´ Rodrı ´guez-Mirasol, Chemical Engineering Depart- ment, School of Industrial Engineering, University of Ma ´laga, Campus de El Ejido, 29013 Ma ´laga, Spain. E-mail: mirasol@uma.es Separation Science and Technology, 40: 3113–3135, 2005 Copyright # Taylor & Francis LLC ISSN 0149-6395 print/1520-5754 online DOI: 10.1080/01496390500385277 3113