Uranium contaminations, both originated from anthropogenic and natural sources, have brought major safety concerns globally. As a prevalent disposal method for low and intermediate-level radioactive waste, solidifying uranium in a cementitous material may fail to immobilize uranium waste due to the material’s porous structure, low thermal stability and poor corrosion resistance. In this study, different dosages (0%, 1%, 3% and 5%) of hematite nanoparticles were added in uranium (VI) contained mortar samples (1.75% added as uranyl nitrate) in order to study the influence of iron oxide nanoparticle on the uranium encapsulation potential. After 28 days of curing the mortar, semi-dynamic leaching experiments were carried out at 90 °C over a period of 28 days. Atomic Absorption Spectroscopy and PERALS spectrometer were utilized to measure the leaching rates of Na and U from the samples, respectively. X-ray Diffraction, Fourier transform infrared spectroscopy and mercury intrusion porosimetry were used to characterize the microstructures and chemical properties of uranium-contained mortar with hematite nanoparticles. In addition, isothermal calorimetry was performed at early ages to evaluate the impacts of hematite nanoparticles on the cement hydration kinetics. Interestingly, compared with samples without hematite nanoparticles, the leached uranium amount from samples containing 1%, 3%, 5% of hematite nanoparticles were decreased by 58%, 17% and 18%, respectively, due to the adsorption of uranium by hematite nanoparticles. Furthermore, the slowest uranium leaching with 1% hematite samples may due to the lowered porosity of the samples, based on Na diffusion and porosity measurements. Calorimetry results showed that adding hematite increased the peak reaction rate and the degree of hydration at 12 h and 24 h. These findings showed that hematite modified mortar can enhance the immobilization effect of uranium, providing a promising safer way of disposing low and intermediated radioactive waste.

Hematite modified cementitious material for uranium (VI) immobilization

251st National Meeting (2016)

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