The uptake of caesium and strontium radioisotopes onto clays

Clay mineral weathering and contaminant dynamics in a caustic aqueous system

“…13a-c). This result is consistent with high illite selectivity for Cs relative to Sr (Jeong et al, 1996;Dyer et al, 2000;Zachara et al, 2002) and the limited density of accessible charged sites in illite (Ͻ 150 mmol c kg Ϫ1 ) for sorption of the hydrated Sr ion. Both Sr and Cs showed near complete sorption to vermiculite platelets after 1 y reaction time as indicated by wet chemistry data (Fig.…”

Clay mineral weathering and contaminant dynamics in a caustic aqueous system

“…As with Ca 2ϩ , adsorption to a wide range of mineral surfaces-including layer silicates and hydrous oxides-occurs dominantly via outer-sphere complexation, consistent with an ion exchange mechanism (Chen et al, 1998;Oscarson and Hume, 1998;Sahai et al, 2000;. Strontium adsorption to layer silicate clays at circumneutral pH is thought to be reversible and outer-sphere (Rafferty et al, 1981;Puls et al, 1989;Gutierrez and Fuentes, 1993;Dyer et al, 2000;Lu and Mason, 2001). Jeong et al (1996) reported higher uptake of Cs than Sr by illite and smectite, and ascribed the difference to the higher hydration energy of Sr.…”

On the driving force of cation exchange in clays: Insights from combined microcalorimetry experiments and molecular simulation

“…Several measurements of the equilibrium constants for ionic exchange in clay minerals, particularly in those of the montmorillonite type, have been reported (Martin and Laudelout, 1963;Fripiat et al, 1964;Robeyns et al, 1971;Maes and Cremers, 1978;Ewin et al, 1981;Dyer et al, 2000), but the enthalpies of exchange were much less frequently determined (Slabaugh, 1954;Barrer et al, 1963;Maes and Cremers, 1978;Ewin et al, 1981;Morel et al, 2007). One difficulty for rigorously defining thermodynamic quantities of reaction in the case of ionic exchange is that the water content in the interlayer may vary between the initial and final states.…”

“…These counterions are the origin of two interesting features: clay swelling and ionic exchange. The former refers to the entrance of water into the interlayer, while the latter involves the replacement of natural counterions like Na + in the clay interlayer by other ions initially in the aqueous solution in contact with the mineral, and the concomitant release of Na + in the solution (Slabaugh, 1954;Barrer et al, 1963;Martin and Laudelout, 1963;Fripiat et al, 1964;Robeyns et al, 1971;Maes and Cremers, 1978;Ewin et al, 1981;Dyer et al, 2000). The swelling properties of clays have been studied extensively, both experimentally (Weiss et al, 1990;Cases et al, 1992;Bérend et al, 1995;Michot et al, 2002;Ferrage et al, 2005;Rinnert et al, 2005;Trausch et al, 2006;Salles et al, 2008) and theoretically (Boek et al, 1995a,b;de Siqueira et al, 1997;Young and Smith, 2000;Hensen et al, 2001;Hensen and Smit, 2002;Whitley and Smith, 2004;Tambach et al, 2004;Liu and Lu, 2006;Smith et al, 2006;Tambach et al, 2006) and are now relatively well understood.…”