[en] In this study polyacrylonitrile fiber (PANF) was hydrolyzed both with sodium and potassium hydroxide solutions using alkali hydrolysing method and hydrolyzed polyacrylonitrile fibers (HPANF) were obtained. These two types of hydrolyzed fibers were compared taking into consideration strontium adsorption capacities and it was decided that the hydrolysis with KOH solution is more convenient. The hydrolyzed polyacrylonitrile fiber was characterized by DTA/TGA, FTIR and SEM analysis. The adsorption behaviors of HPANF towards Sr ions was investigated by batch technique, the parameters affect the strontium adsorption such as the initial pH of the solution, Sr concentration, temperature, shaking time, adsorbent dose (V/m ratio) were determined. The adaptation of the obtained adsorption equilibrium data to Langmuir and Freundlich isotherm models were investigated and some of the thermodynamic values of the system (ΔGo, ΔHo, ΔSo) were calculated.

[en] Sr-90 is a typical fission product with a half life of approximately 30 years. The removal of long lived radiotoxic strontium from liquid radioactive waste is an important issue for the health safety. Besides, it reduces the storage problems and facilitates the disposal of the waste. Several methods are utilized for the removal of strontium from liquid radioactive waste. One of the important methods is adsorption processes using metal oxides. Especially, sorbents such as hydrous oxides of titanium, silicium and zirconium and their mixtures, titanium and zirconium phosphates, crystalline silico-titanate(CST) have a good thermal and radiation stability, chemical stability even in strong acidic media, high sorption capacity and compatibility to immobilisation step. The major disadvantage of synthetic inorganic sorbents is their unsuitable granulometric and mechanical properties to use in column applications. Preparation of homogen and uniform spherical particles of these composite sorbents by sol-gel method improves the flow dynamics for column operation and extends its practical applications in industry. In this study, ZrO₂-SiO₂ composite microspheres were synthesized by sol-gel method. for the sorption of Sr²+. The optimum Sr²+ adsorption conditions were determined by 'Central Composite Design' (CCD). Thermodynamic parameters related to adsorption such as ΔHo, ΔSo and ΔGo were calculated. The adsorption data have been interpreted in terms of Langmuir, Freundlich and D-R isotherms.

[en] A combination of spatially-resolved synchrotron based techniques (μ-XRF, μ-XRD, μ-XANES) was used to study the distribution and speciation of Pu on Opalinus Clay (OPA) after sorption and diffusion processes. μ-XRF maps showed Ca, Fe, and Pu hot spots on the OPA surface of all investigated thin sections. Pu LIII-edge μ-XANES spectra on Pu hot spots confirmed that Pu(IV) is the dominating species on OPA, i.e., the highly soluble Pu(VI) was retained by OPA in the reduced and less mobile tetravalent oxidation state of Pu. Preliminary μ-XRD results indicate that Pu is localized on or in the close vicinity of the Fe(II) mineral siderite and the clay mineral kaolinite. For all samples fluorescence maps with good signal intensity were collected for Pu, Ca, and Fe. In the regions where Pu localizes, the correlation between Pu and Fe was analyzed using the program XY-MAP DISPLAY. The resulting correlation plots do not immediately point towards an unequivocally correlation between the local concentrations of Pu and Fe. However, in all cases where elevated levels of Pu were detected, a moderately enhanced Fe concentration could be established as well. Areas of highest Fe concentrations, however, turned out to be free of Pu. Similar correlated detection of Pu and Fe was observed also in the diffusion sample. Pu L_III-edge μ-XANES spectra of Pu hot spots show a complete reduction of Pu(VI) to Pu(IV) in all samples. Pu(IV) is the dominating oxidation state after sorption and diffusion processes. Preliminary results of μ-XRD measurements indicate that Pu potentially localizes on siderite and kaolinite mineral phases contained in OPA

[en] In argillaceous rocks, which are considered as a potential host rock for nuclear waste repositories, sorption and diffusion processes govern the migration behaviour of actinides like neptunium. For the safety analysis of such a repository, a molecular-level understanding of the transport and retardation phenomena of radioactive contaminants in the host rock is mandatory. The speciation of Np during sorption and diffusion in Opalinus Clay was studied at near neutral pH using a combination of spatially resolved synchrotron radiation techniques. During the sorption and diffusion experiments, the interaction of 8 μ M Np(V) solutions with the clay lead to the formation of spots at the clay-water interface with increased Np concentrations as determined by μ -XRF. Several of these spots are correlated with areas of increased Fe concentration. Np L₃-edge μ -XANES spectra revealed that up to 85% of the initial Np(V) was reduced to Np(IV). Pyrite could be identified by μ -XRD as a redox-active mineral phase responsible for the formation of Np(IV). The analysis of the diffusion profile within the clay matrix after an in-diffusion experiment for two months showed that Np(V) is progressively reduced with diffusion distance, i.e. Np(IV) amounted to ≈12% and ≈26% at 30 μ m and 525 μ m, respectively. (paper)