The iron oxide ion exchanger Ferrix A33E was successfully modified with cerium(III) ions to obtain Ferrix A33E-Ce(III) providing much better sorption properties in relation to the As(V) species. The new material has been characterized using a number of techniques including scanning electron microscopy SEM, nitrogen adsorption/desorption isotherms, Fourier transform infrared spectroscopy FTIR and X-ray photoelectron spectroscopy XPS. At optimal pH 6 the main mechanism of arsenate adsorption on A33E-Ce(III) was electrostatic attraction and formation of monodentate and bidentate surface complexes. The process was exothermic and spontaneous. Unlike the unmodified ion exchanger, A33E-Ce(III) could completely remove arsenic from the arsenate solution at a concentration of 50 mg/dm3 in 60 minutes. Furthermore, the maximum sorption capacity for As(V) was determined to be 60.41 mg/g which almost doubled after modification with cerium(III) ions. It is also worth noting that even after three cycles of sorption/desorption A33E-Ce(III) exhibited a higher sorption capacity than unmodified A33E before the arsenate adsorption. It can be concluded that modifying the sorbent with a small amount of cerium(III) ions boosts its sorption properties significantly, improves effectiveness of water purification and reduces the overall operation cost.