Process for production of activated carbon fibers

A process for producing activated carbon fibers of high adsorption capacity which contain about 80 to about 90 weight percent carbon, about 3 to about 15 weight percent nitrogen, about 2 to about 10 weight percent oxygen and less than 1 weight percent hydrogen, which comprises oxidizing an acrylonitrile based polymer which is a homopolymer of acrylonitrile, a copolymer containing about 60% by weight or more 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, wherein activation is by heating the oxidized fiber in a gas selected from CO.sub.2, NH.sub.3, steam or a mixture thereof at a temperature of about 700.degree. C. to about 1,000.degree. C. for 1 minute to 3 hours while the fiber is allowed to shrink freely, to thereby provide a specific surface area to said carbon fiber of from 300 m.sup.2 /g to 2,000 m.sup.2 /g, a tensile strength of about 20 to about 80 Kg/mm.sup.2, a tensile elongation of about 0.5 to 3% and a tensile modulus of about 1,500 to about 5,000 Kg/mm.sup.2.