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We explored the use of selected layered double hydroxides (LDHs) of different compositions and obtained by means of different routes (i.e., coprecipitation, anionic exchange and reconstruction) as iodine/iodate adsorbents. The influence of speciation (iodide vs. iodate) on iodine uptake was rather strong, resulting in much lower iodide incorporation. The Fourier transform of iodine K X-ray absorption edge data (EXAFS) of all iodate-LDHs showed a single I-O scattering path of 1.8 Å. Thermal stability and leaching experiments showed that the incorporated iodate and iodide were rather loosely bound in the interlayer space and were easily released under heating to 180 °C and leaching with Milli-Q water and brine solution. [ABSTRACT FROM AUTHOR]

In this work, the kinetics of barium sulfate recrystallization has been studied in acidic 0.01 mol dm sodium sulfate solution using Ra and Ba tracers at very low total radium concentration, i.e. less than 10 mol dm. It was found that the system follows the homogeneous recrystallization model and that recrystallization rates, inferred by the decrease of Ra and Ba in the aqueous solution, are fast. Therefore, even at very low concentrations, below the solubility limit, radium will be retained by barium sulfate-a mineral present in the deep underground repository. [ABSTRACT FROM AUTHOR]