In this study, an adsorbent including double amidoxime groups was prepared by graft copolymerization of glycidly methacrylate (GMA) onto poly(ethyleneterepthalate) (PET) fibers using benzoyl peroxide (Bz(2)O(2)) as initiator in aqueous solution. Grafted PET fibers were modified with iminodiacetonitrile (IDAN) in ethanol at 80 degrees C. Afterwards, the nitrile groups were amidoximated by using 6% (m/v) hydroxylamine hydrochloride in methanol solution. The grafted and modificated fibers were characterized by FTIR, SEM and TGA analysis. The removal of Cr(VI) ions from aqueous solution onto amidoximated fibers was studied. The important parameters such as pH, initial concentration, contact time and adsorption temperature on uptake of Cr(VI) ion were investigated. All adsorption experiments of Cr(VI) ions from aqueous solution onto amidoximated fibers were studied by using the batch adsorption method. The results show that the adsorption amount of Cr(VI) ions increased with initial ion concentration, shaking time, temperature but decreased with increasing pH of the medium. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were employed to discuss the adsorption behavior. The adsorption isotherms of Cr(VI) on amidoximated fiber were well described by Langmuir isotherm and the maximum adsorption capacity calculated from Langmuir isotherm model was 125 mg/g. Adsorption processes for Cr(VI) ions onto amidoximated was found to follow pseudo-second order type adsorption kinetics. Thermodynamic parameters, such as change in standard free energy (Delta G), enthalpy (Delta H) and entropy (Delta S), have also been evaluated and it has been found that adsorption spontaneous and endothermic in nature. It was observed that the amidoximated fibers are regenerable by KOH and it is more selective for Cr(VI) ions in the mixed solution of Cr- Pb- Co-Ni -Cd-Cu at pH 2.