Nanometer mixed-valence silver oxide enhancing adsorption of ZIF-8 for removal of iodide in solution.

Abstract Nano mixed-valence silver oxide (Ag 2 O-Ag 2 O 3 ) modified the zeolitic imidazolate framework-8 (ZIF-8) composite (Ag 2 O-Ag 2 O 3 @ZIF-8) was firstly prepared via a simple and efficient method, characterized and applied for iodide ion (I − ) uptake from simulated radioactive wastewater. The results showed that Ag 2 O-Ag 2 O 3 nanoparticles doped and uniformly dispersed on the surface of ZIF-8 matrix. The adsorption capacity of the as-synthesized adsorbents increased with the increasing Ag doped amount, and the maximum adsorption capacity for 20%-Ag 2 O-Ag 2 O 3 @ZIF-8 was 232.12 mg/g. The calculated thermodynamic parameters indicating that the adsorption was a spontaneous and exothermic. It was worth mentioning that each Ag-based adsorbent exhibited high uptake rate of I − , and all the adsorption tests were equilibrated for a few minutes. This could be ascribed to its large specific surface area and the absolutely dominant position of chemical adsorption for as-prepared samples. Furthermore, the adsorption was barely affected by pH and competitive anions (e.g. Cl − , SO 4 2− , CO 3 2− ), even in simulated salt lake water. Additionally, a mechanism explaining the excellent properties for adsorbents could be epitomized into three aspects, namely, the uptake performance of Ag 2 O for I − , the strong oxidization of Ag 2 O 3 for I − , and the adsorption of AgI for I 2 .