Consolidation of Iodine-Laden Adsorbents into Cementitious Waste Forms Suitable for Geological Disposal

Formulation of iodine-laden materials into waste forms suitable for permanent geological disposal is a daunting challenge. In this work, we present a feasible method for incorporating iodine-loaded UiO-66-NH2 and Al2O3-DMAPS (3-N,N-dimethylaminopropyl-trimethoxysilane) adsorbents into low-calcium alkaline cement (type III) to produce consolidated waste forms. The UiO-66-NH2 and Al2O3-DMAPS adsorbents exhibited 248 and 241 mg/g iodine capacity, respectively, upon exposure to iodine in aqueous phase at 25 °C for 48 h. After incorporation into cement matrix, the consolidated waste forms were characterized by X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), and X-ray computed tomography (XCT). The results confirmed the presence of crystalline phases and uniform distribution of iodine-laden adsorbents within the cement matrix. Additionally, the effect of adsorbents loading on the mechanical integrity of the composites was investigated, and the results showed that the total porosity correlated strongly with the compressive strength. However, as the iodine-adsorbent/cement weight ratio increased, the compressive strength decreased, which also reduced the thermal stability of the composite. Lastly, the iodine leaching tests in deionized water confirmed the efficacy of the cementitious waste forms in permanently trapping iodine for safe geological disposal.