Perspectives for the Study of the Diffusion of Radionuclides into Minerals Using the Nuclear Microprobe Techniques

Abstract

The aqueous sorption of cadmium solutions on hydroxyapatite (HAP) single crystals has been studied with the Nuclear Microprobe facility of the Laboratoire Pierre Siie in Saclay (France).By coupling Proton Induced X-ray Emission (PIXE) and Rutherford Backscattering (RBS) analyses, the concentration and distribution of cadmium in the HAP crystals have been measured. The use of different incident proton energies allowed to model the incorporation of cadmium as a function of the analyzed depth. A one dimensional simple diffusion models the incorporation of cadmium along the crystallographic c-axis. The study of sorption kinetics allowed to derive a lower limit (some 10 3 μιτι 2 /5) of the diffusion coefficient according to the shortest contact time of one minute with the solution. The coupling of diffusion with cation exchange as the active sorption processes has been identified, other surface mechanisms being limited. The advantages of using apatites to trap or retard the diffusion of radionuclides in the near and the far field of a nuclear waste repository are discussed.

Applications of NAA, PIXE and XPS for the quantification and characterization of the humic substances/iodine association

“…Its applications to nuclear waste disposal studies [25,26] and to the organic matter behaviour have been already reported in the literature [23,27].…”

Cadmium Uptake by Hydroxyapatite Synthesized in Different Conditions and Submitted to Thermal Treatment

“…However, controversy related to metal sorption mechanisms still remains in the literature (11)(12)(13)(14)(15). Such controversy is certainly related to the insufficient understanding of the physicochemical properties of the HA surface.…”

“…On the other hand, HA shows strong variability in crystallinity, morphology, texture, stability, and solubility when synthesized in different ways and conditions. In the case of cadmium, previous works suggested the occurrence of several sorption mechanisms such as ion exchange (11,12,15), surface complexation (13), diffusion through the solid (15), and coprecipitation (13). However, it is not simple to determine the importance of each mechanism along the sorption kinetic once the amount of Ca 2+ and PO4 3-measured in the solution is partially due to the HA dissolution.…”

In Silico Study of Hydroxyapatite and Bioglass®: How Computational Science Sheds Light on Biomaterials

“…Hydroxyapatite [HA,Ca 10 (PO 4 ) 6 (OH) 2 ] owes its relevance and use as a biomaterial since it constitutes the majority of the mineral phase of bones and tooth enamel in mammalians (Young & Brown, 1982). For sake of completeness, we mention that hydroxyapatite is also studied as an environmental adsorbent of metals and a catalyst (Matsumura & Moffat, 1996;Toulhat et al, 1996). One of the first applications of HA in biomedicine dates back to 1969, when Levitt et al hot-pressed it in powders for biological experimentations (Levitt et al, 1969).…”