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 temperature of a precursor fiber on the microstructure, specific surface, pore-size distribution, and adsorption properties of PAN-based activated carbon hollow fibers (PAN-ACHF) were studied in this work. After the activation process, the BET surface area of the PAN-ACHF and surface area of mesopores in the PAN-ACHF increased very remarkably and reached 1422 m(2) g(-1) and 1234 m(2) g(-1), respectively, when activation temperature is 1000 degrees C. The adsorptions to creatinine and VB12 of PAN-ACHF were much high and reached 99 and 84% respectively. In PAN-ACHF which went through the activation at 700 degrees C and 800 degrees C, the micropore filling mainly occurred at low relative pressures, multimolecular layer adsorption occurred with the increasing of relative pressure, and the filling and emptying of the mesopores by capillary condensation occurred at high relative pressures. But in PAN-ACHF which went through the activation at 900 degrees C, a mass of mesopores resulted in the large pore filling by capillary condensation. The dominant pore sizes of mesopores in PAN-ACHF are from 2 nm to 5 nm. (c) 2006 Wiley Periodicals, Inc.