Removal of radioactive iodine by Cu2O prepared with PVP as an active agent: Role of crystal facets and oxygen vacancy in adsorption mechanisms

Radioactive iodine removal continues to pose significant challenges. In this study, the advantages of crystal facet and defect engineering were utilized to synthesize six types of Cu2O nanocrystals with varying crystal facet exposed, crystal edge exposed, and abundant oxygen vacancies (OVs). Compared to pure {100} and {111} exposed Cu2O, {100}+{111} co-exposed Cu2O exhibited superior adsorption capacity and adsorption rate for iodide ions (I−), achieving a removal efficiency of 96 % for trace I− (0.1 mg/L). Moreover, OVs significantly contribute to iodide ion (I−) adsorption. Experimental and density functional theory (DFT) analyses confirmed that the active sites on {100}/{111} crystal edges possess the highest affinity for I−. The OVs disrupts the charge balance of the Cu2O surface and increases unsaturated coordination sites of Cu, therefore, it significantly enhanced the affinity for I−. This research offers insights into the design of effective I− adsorption materials using crystal facet and defect engineering strategies.