| Summary: | Halloysite/Ag<sub>2</sub>O (Hal/Ag<sub>2</sub>O) nanomaterials were prepared by growing Ag<sub>2</sub>O nanoparticles on the surface of nanotubular halloysite using silver nitrate solution under alkaline conditions. The nanomaterials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N<sub>2</sub> adsorption. Good dispersion of Ag<sub>2</sub>O nanoparticles with average sizes of 6.07 ± 2.5 nm and 8.04 ± 3.8 nm was achieved in the nanomaterials when using different concentrations of alkali. The nanomaterial with 6.36% Ag<sub>2</sub>O (Hal/Ag<sub>2</sub>O-2) exhibited rapid adsorption to iodide (I<sup>−</sup>); adsorption equilibrium can be reached within 100 min. The adsorption capacity of I<sup>−</sup> on Hal/Ag<sub>2</sub>O-2 is 57.5 mg/g, which is more than 143 times higher than that of halloysite. The nanomaterial also showed a better adsorption capacity per unit mass of Ag<sub>2</sub>O due to the better dispersion and less coaggregation of Ag<sub>2</sub>O in the nanomaterial than in the pure Ag<sub>2</sub>O nanoparticles. Importantly, Hal/Ag<sub>2</sub>O-2 exhibited high selectivity for I<sup>−</sup>, and its I<sup>−</sup> removal efficiency was hardly affected by the coexistence of Cl<sup>−</sup>, Br<sup>−</sup>, or SO<sub>4</sub><sup>2−</sup>, as well as the initial pH of the solution. With an excellent adsorption performance, the prepared Hal/Ag<sub>2</sub>O nanomaterial could be a new and efficient adsorbent capable of the adsorption of radioactive I<sup>−</sup> from aqueous solution.
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