Reactive Green HE 4BD was immobilized on polyamide (PA) hollow fibers for beta-Casein adsorption from aqueous solutions. Different amounts of Reactive Green HE 4BD were incorporated on the PA hollow fibers by changing the dye attachment conditions, i.e. the initial dye concentration and the addition of sodium carbonate and sodium chloride. The maximum amount of dye attachment was obtained as 39.4 mu mol/g when the hollow fibers were treated with 3 M HCl for 30 min before performing the dye attachment. beta-Casein adsorption onto unmodified and dye-attached hollow fibers was investigated batchwise. The non-specific adsorption of beta-Casein was low (6.0 mg/g hollow fiber). Dye attachment onto the hollow fibers significantly increased the beta-Casein adsorption (80.7 mg/g). The maximum beta-Casein adsorption was observed at pH 5.0. The desorptions were performed by adding 0.1 M Tris/HCl buffer containing 0.5 M NaSCN or 1.0 M NaCl to the beta-Casein solutions in which adsorption equilibria had been reached. The desorption results demonstrated that the adsorption of beta-Casein to the adsorbent was reversible. (C) 2007 Elsevier Ltd. All rights reserved.