Silver-decorated ZIF-8 derived ZnO concave nanocubes for efficient photooxidation-adsorption of iodide anions: An in-depth experimental and theoretical investigation

Elimination of radioactive iodide (I) from complex solution of used nuclear fuel directly is the optimum scheme in the remediation of iodide released into the environment. However, this assignment represents a tremendous challenge given the combined harsh conditions of strong acidity, high ionic strength, and strong ionizing radiation field. Here, we surmount the challenge by applying silver-decorated ZIF-8 derived ZnO concave nanocubes (CNCs) (denoted as AZ) as a potential photocatalyst and adsorbent for photooxidation-adsorption of I- from simulated radioactive wastewater. The as-synthesized product showed a prominent I- uptake capacity of 129.3 mg g(-1) under visible light with relatively fast kinetic adsorption process as well as remarkable selectivity, strong acid resistance and excellent gamma radiation resistance. The uptake process, with spontaneity and exothermic, followed the pseudo-second-order kinetics and Langmuir isotherm models. The mechanism explaining the excellent properties was investigated systematically and could be epitomized into the following: AZ nanocomposites possessed the cumulative effects of the uptake performance of Ag2O for I-, the photooxidation property of Ag(0)@ZnO CNCs for oxidation of I- to I-2 under visible light. Density functional theory (DFT) calculations further revealed that I-2 was more likely to bind to nearby Ag site yielding AgI, or be trapped readily by AgI to form AgI3. Overall, our work provides a facile and useful pathway toward radioactive iodine elimination.