Macroporous polypropylene (MPP) membranes incorporating poly[sodium (styrene sulphonate)], P(SSNa), and poly[(ar-vinylbenzyl) trimethylammonium chloride],P(ClVBTA) were modified via “in situ” radical polymerization. Modified and unmodified MPP were characterized using SEM and charge density properties. Donnan dialysis was used to transport chromium ions. The results show that the degree of modification varied between 2.5% and 4.0%, and the water uptake percentage varied between 15% and 20%. Experimental data for chromium ion transport (Cr(III) and Cr(VI)) were fitted to a mathematical model, and a correlation coefficient very close to 1 was obtained. The main parameters of this mathematical fit are k and a. These parameters report the concentration of chromium ions that converge in the Donnan equilibrium (k) and the response rate of the modified membrane (a).