Abstract: A fibrous activated carbon having high adsorptivity and excellent mechanical properties is produced by preoxidizing an acrylonitrile-based fiber containing a specific amount of an iron compound at a specific initial heat-treatment temperature and then activating.

Abstract: A process for producing activated carbon fibers of high adsorption capacity which comprises oxidizing an acrylonitrile based fiber, wherein the acrylonitrile based fiber is a homopolymer of acrylonitrile, a copolymer containing about 60% by weight or more of acrylonitrile, or a mixture of polymers such that about 60% by weight or more of acrylonitrile is present in the mixture, in an oxidizing atmosphere at a temperature of about 200.degree. C. to about 300.degree. C. while applying a tension to the fiber until the amount of bonded oxygen reaches about 65% to about 95% of the saturated amount of bonded oxygen of the fiber, wherein the tension applied is such that the shrinkage of the fiber during oxidation reaches about 70% to about 90% of the degree of free shrinkage at the same temperature, and then activating the fiber.

Abstract: A process for producing activated carbon fibers comprising subjecting an acrylonitrile based fiber to oxidation processing in an oxidizing atmosphere at a temperature of about 200.degree. C. to about 300.degree. C. while applying a tension to the fiber until the amount of bonded oxygen reaches about 50% to about 90% of the saturated amount of bonded oxygen followed by activation processing.

Abstract: A tobacco smoke filter capable of selectively removing irritating materials and unpleasant bitter components from tobacco smoke and containing as a filter element nitrogen-containing activated carbon fibers produced by oxidizing acrylonitrile polymer fibers and then activating the oxidized fibers.