The influence of surface modification of activated carbon on the adsorption of methyl mercaptan in N-2 was investigated. The modification of the activated carbon was carried out by treatment with HNO3/H2SO4 solutions, heat-treatment in Ar, and adsorption of cetylamine. Acid-treatment increased the adsorption of methyl mercaptan compared with the original activated carbon, and the adsorbed amounts increased with ratio of H2SO4 in HNO3/H2SO4 solutions. This result suggests that hydrogen bonding between acidic groups formed by acid-treatment and thiol groups of methyl mercaptan plays a role in adsorption of methyl mercaptan on activated carbon. (c) 2006 Elsevier Inc. All rights reserved.