Bimetal ZIFs-derived Cu0 embedded in nitrogen-doped carbon framework activation of molecular oxygen for efficient iodide elimination

Effectively removing radioiodine from radioactive wastewater is of great significance for the environment and human health. In this work, nitrogen-doped carbon matrix embedded zero-valent copper (CuxZn1−x@NC) nanocomposites was successfully prepared from copper-zinc bimetal zeolitic imidazole frameworks precursors (CuxZn1−x-ZIFs) through a pyrolysis method and applied to efficiently remove iodide. The physicochemical properties of the resultant materials were completely characterized and the results clearly implied that the morphology, Cu0 contents, pour structure and specific surface area could be tuned by regulating the Cu/Zn molar ration in ZIFs precursors. Adsorption experiments revealed that the as-fabricated nanocomposites displayed high adsorption capacity of 235.5 mg g−1 at pH = 3, as well as relatively fast dynamics and high selectivity. Interestingly, CuxZn1−x@NC exhibited an excellent reusability. The iodide adsorption amounts of regenerated materials was nearly 2 times superior to that of the initial one. Based on the characterization results of the regenerated adsorbent before and after adsorption, the iodide removal mechanism was proposed to be electrostatic adsorption of iodide in the material surface, followed by oxidation reaction of iodide to iodate by reactive oxygen species generated from zero-valent copper activated molecular oxygen reaction. The findings of this study offer a feasible strategy for the intensive treatment of radioactive iodine containing wastewater.