Dehydration and rehydration of Zn-hydroxy sulfate minerals with interrupted decorated hydroxide sheets

The negatively charged surface of gordaite hydroxide layer, caused by the occupation of apical position of Zn tetrahedra by Cl− determine dehydration behavior, similar to that of montmorillonite and vermiculite structures. On heating, gordaite and Ca-gordaite form three and two pillared structures with different sizes of interlayer space and different amount of water molecules for each phase. The rate of dehydration and/or rehydration and particular quantity of derived water molecules is controlled by the interlayer cations. In accordance with the high ionic potential of calcium, the dehydration of Ca-gordaite occurs only on heating and the rehydration proceeds at very low RH conditions. To the contrary, the much lower ionic potential of sodium causes the formation of dehydrated gordaite phases by both heating and by adsorption. Similarly to the montmorillonite and vermiculite - these two gordaite minerals can be expected to be used for both cation exchange for interlayer cations and anionic exchange of apical Cl− anion.