Charge location effect on the hydration properties of synthetic saponite and hectorite saturated by Na~+, Ca~(2+) cations: XRD investigation

摘要

This paper aims at comparing the effect of charge location on the hydration properties of two trioctahedral synthetic minerals: saponite and hectorite. The samples were characterised by a layer charge of 0.4 charge per half unit cell and were saturated with Na~+ or Ca~(2+). The hydration behaviour was studied by determining the structural characteristics which were obtained by modelling XRD patterns.rnXRD patterns were recorded under controlled relative humidity (RH). The hydrated states of Ca-hectorite were more homogeneous than those of saponite whereas the transition from 1W to 2 W occurred at lower RH rates for saponite than for hectorite. For heterogeneous samples, the 1W and 2W layers were stacked randomly fashion for hectorite. Na-saponite-0.4 and Ca-saponite-0.4 were made up of types of layer; one water layer (1W) and two-water layers (2W). The stacking of these layers showed some segregation.