A porous hollow fiber membrane was modified with diethanolamine (DEtA) group by radiation-induced graft polymerization and subsequent chemical modifications. Adsorption behavior of anions was investigated by permeating anion solutions through the membrane. The binary anions (NO₃^- and SO₄^2-) were transported tothe DEtA group by permeating the aqueous solutions. Negligible diffusional mass-transfer resistance of NO₃^- and SO₄^2- ions to the DEtA group and instantaneous displacement of the sorbed NO₃^- with SO₄^2- ions were demonstrated in the permeation mode.