The uptake of radioisotopes onto clays and other natural materials

Abstract

Montmorillonite and illite clays were examined for their ability to take up cesium and strontium radioisotopes from solution. Uptakes onto near homoionic Na, Ca, Mg and Sr clays were assessed by distribution coefficients measured at different Na, Cs, Mg, Ca and Sr solution concentrations. Some experiments were carried out at different pH, and to check the effect of differing anions. In addition measurements of the uptake of ruthenium species were made.

The uptake of radioisotopes onto clays and other natural materials

“…12 The results for 9~ leaching from clinoptilolite/cement employed synthetic sea water as leachant and was several orders of magnitude faster than those reported in this study. The zeolite had been calcined prior to encapsulation but this has been shown to have only a small effect on the leach rate.…”

“…12,13 Preparation of radioactive forms of the clays 5.0 g of each clay were tared into separate plastic bottles, and 50 ml of carrier free solutions of 137Cs or 9~ in doionised water added. The bottles were sealed and rotated on a mineralogical roller for at least 2 days.…”

The uptake of caesium and strontium radioisotopes onto clays

“…The high cation exchange capacity (0.75 meq g 21 ) may arise from isomorphous substitution of Fe 2z into octahedral sheet positions. 2 Diffractograms of the Surrey Earth showed sharp peaks at 1.54,0.45,0.33 and 0.30 nm, and those of the illite showed peaks at 0.99,0.50,0.45 and 0.35 nm. Both sets of data corresponded to literature values.…”

“…The changes in selectivity as a function of concentration have been noted above and further evidence of similar changes can be found in earlier work. 2 Comparison to other work. Table 5 lists the free energy values obtained by other workers for similar cation exchanges in other montmorillonites.…”

27 Radiochemistry

“…This is a very complex business but work has been done on the behaviour of caesium, 203,204 strontium, 203 samarium, 205 and neptunyl 204 cations and iodide 203,204 and selenide 205 anions on various types of bentonite, so that in some cases apparent diffusion rates for ion movement could be measured. Similar work has been done for neptunyl ions on silica gels 206 and on illite, 207 caesium, strontium and ruthenium ions on illite and montmorillonite, 208 caesium, 209 [ 32 Si]silicate, 210 thorium and uranium 211 on clay and radium 212 on kaolinite and montmorillonite. More detailed studies in which the effect of variation of pH and carbonate ion concentrations upon the adsorption of neptunyl(V) onto hydragilite 213 and neptunyl(V) and cobalt(II) onto titania 214 have also been reported.…”