A diol group and tannin were immobilized on a polyethylene microfiltration (MF) membrane by radiation-induced grafting of glycidyl methacrylate (GMA) and subsequent chemical modifications. A quantitative hydrolysis of the GMA-grafted membrane with sulfuric acid provided a diol group density of 7.7 mol per kg of the starting MF membrane. Coupling of the GMA-grafted membrane with tannin resulted in a 4% molar conversion of the epoxide group. Breakthrough curves of bovine serum albumin (BSA) and ferrous ions during permeation of their solution across the modified membrane were compared. The breakthrough curves resulting from BSA adsorption onto the grafted polymer branches containing the diol group and tannin were insensitive to the residence time of the solution across the membranes, whereas the breakthrough curve of the ferrous ions was dependent on the residence time because of their lower binding rate to the tannin immobilized on the grafted polymer branches.