Pressure‐Induced Hydration Effects in the Zeolite Laumontite

Abstract

The hydration level of minerals is an important indicator of the conditions prevailing during their formation and during any subsequent geological transformation. The precise water content of mineral zeolites, often highly sensitive to pressure and temperature due to their microporous structure, is particularly key in estimating rock porosity. The presence of the mineral zeolite laumontite near petroleum deposits, for example, can significantly reduce rock permeability, which may limit the production potential of the reservoir.[1] However, since laumontite readily partially dehydrates at ambient conditions [1,2] the exact composition during formation and subsequent diagenesis remains a key question. Neuhoff and Bird [1] [3] and only becomes fully hydrated at elevated pressures. Lee et al. [4][5][6] recently showed that another natural zeolite, natrolite, undergoes pressure-induced overhydration. As a consequence, it is imperative that we can determine the structure of such zeolites at nonambient conditions if we are to understand, not only their geochemistry, but also to assess the impact of extreme conditions on their suitability as, for example, nuclear-waste-containment and barrier materials. Here, we show using computational methods that laumontite can transform from the low-water "leonhardite" composition to the fully hydrated structure under the influence of pressure.Laumontite (LAU·18 H 2 O; Figure 1) is one of the more common natural zeolites. The structure comprises channels bounded by eight tetrahedral units, parallel to the c axis, that contain Ca 2+ ions coordinated to the framework and water (labeled [2] W2 and W8), together with an additional hydrogen-bonded water network (W1 and W5

The effect of pressure on open-framework silicates: elastic behaviour and crystal–fluid interaction

“…An additional P-induced expansion phenomenon was observed in laumontite, ideally White et al (2004). Such a study predicted the occurrence of full hydration at moderate pressures, which was then confirmed by the experiments, evidencing that, when pressure is applied, the structural stability of the laumontite-type framework increases because of the fully occupied water network.…”

Interplay of water, extra-framework cations and framework atoms in the structure of low-silicazeolites: the case of the natural zeolite Goosecreekite as studied by computer simulation

“…69 We have since developed methods for simulating the dehydration behaviour of zeolites, using energy minimum pathways to follow the thermodynamic loss of water. 70 Furthermore, the procedure can provide valuable information regarding the geochemistry of zeolites, as has recently been shown in a high pressure modelling of the effect of hydration levels in the zeolite laumontite 71 where the predicted pressure induced increase in water content has also been demonstrated experimentally. 72 In the present paper, we describe the details of the approach we devised for the successful study of hydration of zeolites, using Goosecreekite as a model material.…”

Supramolecular Organization in Confined Nanospaces

“…Water was the first species to be introduced through high‐pressure into zeolites, yet the first structural reports on pressure induced hydration or overhydration (PIH) came many years later ,. Since then, many studies have discussed the pressure‐driven injection of water inside hydrophobic, or hydrophilic matrices, including aluminophosphates, which have advanced our understanding of water organization in tight spaces, and are systematically discussed in dedicated accounts ,,,…”