Highly porous cerium oxide prepared via a one-step hard template method as an extremely effective adsorbent for arsenic species removal from water

In contrast to the previously proposed methods for the production of cerium oxide, most of which are complex and highly demanding, this study describes an easy and relatively inexpensive approach to the synthesis of highly porous (SBET > 170 m2 g–1) cerium oxide beads via the one-step hard template method. The product of the synthesis is an extremely effective adsorbent of arsenic species from water. The beads exhibit relatively high mechanical strength and can be used in adsorption directly. A comprehensive study of the effect of synthesis conditions on the properties of the final cerium oxide is presented. This study reveals that the point of zero charge of the ceria reaches 10 (the highest among already reported). The UV–Vis and XRD results indicate that beads are composed of CeO2 nanoparticles, on the surface of which the atomic percentage of Ce(III) determined by XPS is 26 %. The adsorption capacities of As(III) and As(V) species at pH 7 are 230 mg g−1 and 111 mg g−1, respectively; and outperform most reported adsorbents. It has been demonstrated that more than 50 % of As(III) is oxidised towards As(V) on the surface of ceria, while Ce(IV) on the surface is reduced, and the atomic percentage of Ce(III) increases by about 9 %. The composition of the ceria surface at the nano level is crucial in the As species adsorption due to the complexity of the process.