Liquid-phase polymer-based retention (LPR) is a novel technique for eliminating, concentrating and separating pollutants from aqueous effluents. Using the washing method, LPR can provide a retention profile that contains the contributions of all the factors associated with the retention. To advance the LPR technique and further our understanding of polymeric systems in aqueous solutions, a model of the retention profile was developed and applied to Cu2+ retention. The removal of Cu2+ was studied with LPR experiments employing various polymers, a range of pH values (2.0, 3.5, and 5.0) and different interfering species (Co2+, Ni2+, and Zn2+). The resulting retention profiles were simulated from the experimental data. The results revealed constant R (syst) values at pH 5.0. However, at pH 3.5 and 2.0, R (syst) by PVPA exhibited the following behavior: Cu2+ > Zn2+ > Co2+ > Ni2+ and Cu2+ > Co2+ a parts per thousand Ni2+ > Zn2+, respectively. In addition, our results suggested that at pH 6.0, Co2+, Zn2+ and Ni2+ affected the Cu2+ retention by PVPA by decreasing the retention capacity due to the competition of ions for functional groups on the polymer chains, whereas at pH 2.0, the preferential retention of Cu2+ and Ni2+ was observed.