Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation time of a precursor fiber on the microstructure, specific surface area, pore-size distribution, and adsorption properties of PAN-based activated carbon hollow fibers (PAN-ACHF) were studied in this work. The BET surface area of PAN-ACHF and surface area of mesopores gradually increase with activation time extending, and reach the maximum values, 780 and 180 m(2) g(-1), respectively, when fibers are activated at 800 degrees C for 100 min. The adsorption ratio to creatinine changes little with activation time extending and all values over all activation time are above 90%. The adsorption ratio to VB12 gradually increases with activation time extending before 60 min, and then becomes relatively constant from 60 to 100 min. The number of pores on the surface of PAN-ACHF increases with activation time extending. The amount of mesopores in PAN-ACHF made of fibers activated for different time increases with activation time extending and the dominant pore sizes of mesopores in PAN-ACHF range from 2 to 5 nm. (c) 2005 Wiley Periodicals, Inc.