Water-soluble polymer poly[3-methacryloylamine)propyl)trimethyl ammonium chloride, P(ClMPTA) and the copolymer with 4-vinyl pyridine, poly[(3-methacryloylamine)propyl) trimethylammonium chloride-co-4-vinyl pyridine], P(ClMPTA-co-4VP) were synthesized by radical polymerization, at different feed mole ratios ClMPTA:4VP 1:1, 1:2, and 2:1. The copolymer compositions were determined by FT-IR and H-NMR spectroscopy and analyzed by TG-DSC. The liquid-phase polymer-based retention (LPR) technique was used to study the water-soluble polymers' arsenic removal properties. The solution's conductivity properties were evaluated at different pH. The copolymers can bind more selectively divalent anionic arsenic species from an aqueous solution (pH 8 a parts per thousand yen pH 6 > pH 4). Assays for the mol ratio copolymer: As(V) 75:1, 37.5:1, 20:1, 10:1, and 5:1 at arsenic concentrations of 10 and 37.5 ppm were carried out. Apparently, the behavior of the copolymers with the solution's pH was similar to pure cationic homopolymer; however, when the retention capacity was expressed as real mass of quaternary ammonium comonomer, the retention values were enhanced for lowest mol ratio 10:1 and 5:1. The retention capacity of exchanger with quaternary ammonium group was improved in presence of a weak base 4-vinyl pyridine comonomer, differently to the behavior showed by those copolymers of ClMPTA with acrylic acid groups as comonomer.