KOH activation of a mesophase pitch produces very efficient carbons for the removal of sulfide in aqueous solution, increasing the sulfur oxidation rate with the degree of activation of the carbon. These carbons are characterized by their graphitic structures, with domains of sizes of around 20 nm, and a moderate concentration of surface oxygen groups (0.2-0.5 mmol.g(-1)) dominating the basic groups. Because the activation leads first to a strong development of the micropores and later to a development of the mesopores, the surface area values are always high, reaching values of as high as 3250 m(2).g(-1) in the most activated carbon, with a volume of mesopores of as high as 44% of the total pore volume. In the presence of this carbon, the sulfide oxidation rate is 100 times higher than that found for a commercial activated carbon, the results indicating that the porosity of the carbon, especially mesoporosity, plays a role more important than the structure or the chemical nature of the carbon in the kinetics of sulfide oxidation to different polysulfides.