Prediction of solid/liquid distribution coefficients of radiocaesium in soils and sediments. Part two: a new procedure for solid phase speciation of radiocaesium

K/Ca and NH4/Ca selectivity of hydroxyaluminum-interlayered vermiculite and montmorillonite: Contribution from regular and frayed edge exchange sites

“…The value of the intercept, attributed to the action of FES, agreed well with the FES capacity obtained for freshwater sediments (Wauters et al 1996). It is expected that a very low K or NH 4 loading may occur in the RES for low PAR or AAR values.…”

“…Interlayering with a higher amount of more basic Al also favored the contribution from FES in both Vt and Mt. Based the intercept values, it appears that NH 4 may be slightly more competitive than K in getting adsorbed by the FES, but not in the same magnitude as the values reported previously (Cremers and Paterson 1991;Sinnaeve and Glast 1991;Wauters et al 1996). It may be worth noting that the relative abundance of FES of different clay specimens and a slightly higher preference of NH 4 to K should be instrumental at low K-or NH 4 -saturation.…”

“…The data of the present and previous studies (Saha et al 1999) were analyzed to estimate the overall K/Ca and NH 4 /Ca adsorption selectivity coefficients (K e ) and the contribution of regular and frayed edge exchange sites according to the method of Wauters et al (1996). Interaction of HyA ionic solutions with Vt and Mt resulted in a depletion of Al concentrations in the parent solutions, suggesting that HyA ionic species were fixed on the clays.…”

“…Rather, on some of the clay specimens, such as on Mt and HyA (OH/ Al=2.5)-Vt, the similarity of the K c value for K/Ca and NH 4 /Ca adsorption indicated that both K+ and NH 4 + ions might be equally competitive for the adsorption surfaces. It was reported that NH 4 showed a distinctly high competitiveness compared to K, in the FES of natural micaceous clay minerals and that the NH 4 /K selectivity values in their FES could be about 5 to 6 (Cremers and Paterson 1991;Sinnaeve and Olast 1991;Wauters et al 1996). Although we assume that the higher K/Ca and NH 4 /Ca selectivity of the synthetic HyA-Vt/Mt complexes might have resulted from their mica (K-depleted)-like interlayer characteristics, they were very different from natural micaceous clay minerals in terms of their preference for NH 4 relative to K. Saha and Inoue (1997) also observed that for these HyA-Vt/Mt complexes, the adsorption, exchange, and fixation behavior NH 4 and K were similar.…”

“…The FES usually show a much higher K/Ca selectivity than the RES (Beckett and Nafady 1967;Fanning et al 1989). Cremers and Paterson (1991), Sinnaeve and Olast (1991), and Wauters et al (1996) observed a distinctly higher competitiveness of NH 4 with K in the FES of natural micaceous clay minerals. The NH 4 /K selectivity values in the FES of micaceous clay minerals reported by these authors were generally around 5.…”