Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate aqueous solution, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of pretreatment concentration Of ammonium dibasic phosphate aqueous solution 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 Brunaner-Emmett-Teller (BET) surface area of the PAN-ACHF and Surface area of mesopores in the PAN-ACHF increases and reaches 513 m(2) g (1) and 66 m(2) g(-1) respectively when the concentration of ammonium dibasic phosphate aqueous solution is 4%, (wt %). The adsorptions to creatinine are much high, reach more than 90% over all the concentration Of ammonium dibasic phosphate aqueous solution. The adsorptions to VB12 of PAN-ACHF reach 86% when the concentration of ammonium dibasic phosphate aqueous solution is 4% (wt %). The dominant pore sizes of mesopores in PAN-ACHF range from 2 to 5 nm. (C) 2010 Periodicals, Inc. J Appl Polym Sci 116: 2023-2028, 2010