Volume 110, Issue 3

The activated carbon (AC) was modified by molecules of quinoline (Q) and the new prepared AC impregnated by Q was characterized using Fourier transform infrared (FTIR), Raman spectroscopy, surface measurements, scanning electron microscope (SEM) and transmission electron microscope (TEM). These analytical techniques demonstrated a successful preparation of AC-Q as a new material which was examined for its sorption behavior for natural uranium. The sorption results by batch mode indicated the optimum conditions for 94.5% removal of U(VI) ions at pH 4.7 and an equilibrium contact time of 90 min. The analysis of sorption data revealed that the pseudo-second-order and Langmuir were more fitted than other estimated models. The sorption capacity of U(VI) was ∼63 mg/g onto AC-Q as adsorbent martial. The thermodynamic data demonstrated that the sorption of uranium is endothermic and spontaneous. New mechanism was supposed based on the role of the abrasive material quinoline on the mechanical removal of uranium from aqueous solution.

AlBaNi-LDH nanoparticles have been synthesized by the co-precipitation method. A series of characterization analyses (Scanning Electron Microscope, Energy Dispersive X-ray, Transmission Electron Microscope, X-ray Diffraction, Atomic Force Microscope, and Infrared spectroscopy) proved that the surface structure of AlBaNi-LDH nano-particles was the key mechanism for UO 2 2+ adsorption. The synthesized product showed good performance in UO 2 2+ adsorption efficiency in neutral pH with a maximal adsorption capacity of 137 mg/g. The results demonstrated the adsorption process fitted well with pseudo-second-order and Langmuir isotherm models. Also, the effects of coexisting ions and different eluents are briefly described. These results confirm that AlBaNi-LDH is an effective material for the adsorption of UO 2 2+ from an aqueous solution with reusable availability.

In this work the separation efficiency of the DGA and Ln extraction chromatographic resins has been investigated as a function of absorbed dose induced by alpha radiation. It was found that the resins show good stability towards alpha radiolysis, both maintaining high weight distribution ratios (and resin capacity factors) with the absorbed dose, calculated as if the complete alpha energy would be absorbed only in the resin material. However, the results obtained for Ln resin indicates that the method used in this work (extractive distribution ratio) to investigate alpha radiolytic behaviour is not appropriate. The reason is likely the strong acid dependency of this particular extraction system. The behaviour of the DGA resin towards alpha radiolysis was compared to alpha radiolysis in ordinary liquid-liquid extraction of an organic solvent based on the same extractant, TODGA, dissolved in n -dodecan. It was found that the alpha radiolysis rate of TODGA is about 5 times higher in liquid-liquid extraction where the complete energy of the alpha particle is deposited within the solvent, compared to the DGA resin. This indicates that in the heterogeneous DGA resin system, only 20% of the alpha energy is actually deposited to the organic solvent layered onto the particles of the DGA resin.

A new glass solidification process aims at radioactive iodine waste was explored in order to reduce the possible harm to environment. Samples with different iodine content in silver-coated silica gel were pretreated by hydration device at 300 °C and then sintered at relatively low temperatures (500, 550 and 600 °C). XRD results show that AgI is mainly chemically fixed in the glass network with some AgI particles being physically wrapped by the glass. Moreover, as the sintering temperature reached to 550 °C, B element crystallized. SEM-EDS results show that Ag and I elements are enriched, while the other elements are evenly distributed. AFM results showed that the sample surface becomes rougher as the iodine content increases in the silver coated silica gel. The FT-IR results show that the structure of the sintered sample is mainly composed of [BiO 3 ], [BiO 6 ] and [BO 3 ]. This study provides a new sintering method by hydration device for the treatment of radioactive iodine waste.

This study investigates the physicochemical and thermal properties of styrene–butadiene rubber (SBR) nanocomposite foam. Nano-calcium carbonate (CaCO 3 ) was prepared from eggshells (ESs) waste. Sponge rubber nanocomposites were prepared and were irradiated by electron beam (EB) radiation at 25, 75, and 150 kGy. Their physicochemical properties, including foam density, compression set (CS), hardness, abrasion loss, and expansion ratio, and their thermal stability were investigated. The physicochemical properties were enhanced by adding 2.5 phr of a foaming agent. Among the composites examined, the foam composites containing nano-CaCO 3 had the lowest CS, abrasion loss, and expansion ratio and the highest hardness and foam density. The results confirmed that the thermal stability was improved by incorporating nano-CaCO 3 into the SBR foam and as the radiation dose increased. The sponge containing nanoclay demonstrated an intermediate behavior, whereas that with CaCO 3 nanoparticles showed low average cell diameter and size and high cell wall thickness. The radiation process enhanced the foam density, CS, abrasion loss, hardness, and thermal property of the developed nanocomposites by inducing the formation of intermolecular crosslinks within the composite matrix . The results showed that physicochemical properties improved by increasing the radiation dose at 25 kGy.

China is considering Beishan granitic formation (Gansu Province, China) as the site for high-level radioactive waste (HLW) repositories. Thus, it is crucial to understand the transport behavior of radionuclide in Beishan granitic media under disposal conditions. In this context, the co-transport of U(VI) (as the representative of radionuclides) and bentonite colloid (BC, from erosion of compacted bentonite) in particulate Beishan granite was studied as a function of important in-situ factors, such as BC concentration, ionic strength, pH and flow rate. We found that the increase of BC concentration (BC = 240–480 mg/L) did not affect the transport of individual BC, whereas it significantly facilitated the transport of U(VI). The increase of ionic strength ( I  = 0.001–0.01 M NaCl) or decrease of pH (pH = 7.50–5.40) obviously inhibited the BC transport, where these inhibiting effects were relatively slight for the transport of U(VI). The increase of flow rate significantly facilitated both the transport of BC and U(VI). Finally, a two-site kinetic attachment/detachment model was applied to describe the breakthrough curves of individual and co-transport of BC. The experimental and modeling results of this study have a significant implication on the safety assessment of HLW repositories built in granitic formation.