Adsorption of Arsenate in Water by Zirconia-halloysite Nanotube Material

Drinking water contaminated with arsenic for a long time will inevitably lead to serious human health problems. Suitable adsorbent for arsenic removal from water is an urgent but a challenging task. In this study, halloysite nanotubes-supported ZrO2 (ZrO2/HNT), a novel and efficient arsenate adsorbent, was prepared using a straightforward hydrothermal method. Its morphology and structure were characterized. ZrO2 nanoparticles with monoclinic phase were well dispersed on the outer walls of halloysite nanotubes. And the ZrO2/HNT could effectively remove As(V), achieving adsorption equilibrium within 30 min. The saturation As(V) adsorption capacity was 27.46 mg/g at 25 degrees C. Its adsorption capacity decreased with the increase of the solution's pH. Coexistent ions (except phosphate) showed little effect on adsorption performance of As(V). The As(V) adsorption kinetics fitted well with pseudo-second-order modeland the As(V) removal processes were endothermic which was verified as chemisorption reactions based on calculation of Gibbs free energy and Dubinin-Radushkevich (D-R) isotherm model. Fourier transform infrared (FT-IR) and X-ray photoelectron spectrometer (XPS) study indicated that the As(V) adsorption processes mainly proceeded through ligand exchange between As(V) and hydroxyl groups on the surface of ZrO2 in the ZrO2/HNT and formation of inner-sphere surface complexes. This study suggest that the as-synthesized ZrO2/HNT is a potential candidate for practical applications of As(V) removal from water.