A novel halloysite-CeOx nanohybrid for efficient arsenic removal

In this work, halloysite-CeOx (x = 1.5-2.0) nanocomposites were prepared using a redox-precipitation method, and the As(III) removal performance of the obtained materials was evaluated. These composites were formed by supporting CeO2 nanoparticles on the chemically modified halloysite substrate. The modification of halloysite using a facile NaOH treatment dramatically increased the inner-surface and inner hydroxyl groups. These increased groups significantly enhanced the dispersion of the coating of CeO2 nanoparticles due to electrostatic interactions. The specific surface area and pore volume of the optimized Hal(0.01)Ce composite was 91.1 m(2)/g and 0.16 cm(3)/g, respectively. This composite exhibited an excellent As(III) adsorption capacity (209.3 mg/g CeO2), which was much higher than the unmodified halloysite-CeOx composite (158.5 mg/g CeO2) and unsupported CeO2 nanoparticles (61.9 mg/g). The As(III) adsorption mechanisms on this composite involved the formation of surface complexes and oxidation of partial As(III) followed by As(V) adsorption. In addition, the Hal(0.01)Ce composite also possessed selective adsorption for As(III) in the presence of coexisting ions and maintained 91.4% of the As(III) removal efficiency after three regeneration cycles. These results demonstrate that this composite can be used as a potential candidate for As(III) removal from contaminated water.