The removal and separation of Co-60, Sr-90, and Cs-137 radioisotopes from nitrate aqueous solutions were studied by competitive transport across cellulose triacetate plasticized membranes using organophosphorous acids compounds (D2EHPA, Cyanex 272, Cyanex 301 and Cyanex 302). Competitive transport of trace radionuclides ions from 0.10 M NaNO3 aqueous solutions across polymer inclusion membranes containing cellulose triacetate as the support, D2EHPA as the ion carrier and o-nitrophenyl pentyl ether as the plasticizer provide the selectivity order: Co(II) > Cs(I) > Sr(H). The affinities of the radioisotopes investigated for Cyanex 272 and Cyanex 302 follow the order Cs(l) > Sr(II) > Co(H). The influence of ion carrier acidity on cation transport selectivity and effectiveness was explored. The results show a linear decrease of permeability coefficient values for Co(II) with an increase of pK(a) values of ion carriers. A long-term transport experiment was carried out to demonstrate the durability of polymer inclusion membranes.