Removal of iodide from aqueous solutions using a silver-modified ZnAl layered double hydroxide

Abstract

The removal of radioactive iodine from aqueous solutions is of great concern due to its high environmental mobility and toxicity. To improve the removal ability of layer double hydroxide (LDH) for iodide (I−), Ag-modified Zn3Al1-LDH (Ag@Zn3Al1-LDH) was prepared, characterized, and applied as an adsorbent for I−. Results indicated that the silver was included in Zn3Al1-LDH hybrid materials in the form of Ag2CO3, Ag2O, and Ag (0) nanoparticles and that the Ag contents in the Ag@Zn3Al1-LDH could be easily controlled by the amounts of Ag source added in the synthesis process. The Ag@Zn3Al1-LDH exhibited high adsorption capacity to iodide, and the adsorption capacity of the sample containing 12.2 wt% Ag was as high as 256.0 mg/g, which is 35.6 times higher than that of Zn3Al1-LDH. Furthermore, the Ag@Zn3Al1-LDH exhibited high selectivity for iodide and could function in a wide range of pH. Iodide was removed through cooperative effects mechanisms including the chemical adsorption of Ag2O and Ag2CO3, ion exchange of Zn3Al1-LDH, and the surface complexation of Zn3Al1-LDH for iodide. This work indicated that Ag@Zn3Al1-LDH could be a potentially efficient material for the removal of iodide from wastewater.