Swelling and Structural Organization of Saponite

The structural formula of Kozfikov saponite (Czechoslovakia) is as follows: $N{a_{0.005}}C{a_{0.22}}{K_{0.01}}[S{i_{3.30}}A{l_{0.68}}F{e^{3 + }}{}_{0.02}][M{g_{2.50}}F{e^{2 + }}{}_{0.26}F{e^{3 + }}{}_{0.24}]{O_{10}}{(OH)_2}.$ Saturated with 6 different cations (Li, Na, K, Ca, Mg, Ba) its swelling in ethylene glycol, glycerol and water and its homogeneous hydration extents according to the relative humidity have been studied. Our results were compared with those found for montmorillonites, beidellites and vermiculites in order to estimate the respective influence of the surface charge density and the charge localization on the swelling properties. The three-dimensional organization of the saponite is more or less affected by random stacking faults and by multiple b/3 translations according to the exchangeable cation, the swelling state and the nature of the solvation liquid. Our experimental results indicate that the three-dimensional order met in the hydrated saponites can be explained by an anchoring of the layers towards each other by chains made up of cation -dipole interactions and of hydrogen bonds between negatively charged surface oxygens and the interlayer water. This type of interlayer link is relatively weak. It is therefore easy to introduce stacking faults in these edifices in particular by grinding of the samples.