In this study, a reactive fibrous adsorbent was prepared through the grafting of 4-vinyl pyridine monomer onto poly(ethylene terephthalate) (PET) fibers for the removal of Congo red (CR) dye from an aqueous solution with the batch adsorption method. Effects of various parameters such as the grafting yield, pH, treatment time, and initial dye concentration on the amount of adsorption of the dye onto the reactive fibers were investigated. The effective pH was 4.0 for adsorption on grafted PET fibers. The sufficient time to attain equilibrium was 150 min. The maximum adsorption capacity of the reactive fibers for CR was 17.3 mg/g of fiber. The rates of adsorption conformed to pseudo-second-order kinetics with good correlation. The adsorption isotherm of CR fit a Langmuir-type isotherm. The reactive fibers were stable and regenerable by acid and base without loss of activity. (c) 2007 Wiley Periodicals, Inc.