Currently, the use of polymers marks a strong growth in several areas namely the industry, the Medicine, this is due to its various features such as their low cost, light weight and excellent chemical stability. Polysulfone (PSU) is one of the classes of technical polymers with high thermal, oxidative and hydrolytic stability, moreover it is more resistant to molecular degradation, it is for the reason of these excellent properties that the best way to treat waste using it in the synthesis of polymer membranes. For the present work we have studied the effect of the weight average mass (Wm) of the PSU polymer support on the evolution of the Cr (VI) ion extraction process. Indeed, to develop the membranes, we adopted the same polysulfone PSU polymer with the following three masses Mp: 35,000, 26,000 and 22,000 g / mole, and the same extractive agent EDTA. The prepared membranes were characterized, using the IR spectroscopic technique which shows the integration of the EDTA agent into the polymer matrix, whereas the SEM technique made it possible to characterize the morphology as well as the porosity of these membranes. These membranes were adopted to carry out the process of the extraction and the elimination of Cr (VI) ions, in order to study the influence, of the weight average mass (Wm) of the support polymer, of the initial concentration C0 in substrate and temperature factor on the evolution of the macroscopic parameters (initial flow J0, permeability P) and microscopic (association constant Kass and apparent diffusion coefficient D*), as well as the determination of the activation parameters (Energy Ea , entropy ΔS♯, enthalpy ΔH♯). The results show that there is a clear influence mass average weight factor (length of support polymer chains (PSU)) on the evolution of these parameters, when the(Wm)of the PSU polymer decreases the performance of the membrane becomes better