Modification of Hg complexes in layered silicates with temperature: an in situ XAS study

This work will address the thermal evolution (variation in oxidation state, disproportionation reactions) of Hg(II), adsorbed by two different layer silicates (montmorillonite and vermiculite) via XAS spectroscopy at increasing temperature. From the XANES analysis we could recognize significant structural differences between Hg-treated montmorillonite and vermiculite even at room temperature. At increasing temperature Hg is not easily removed from the silicate layer and it could be identified in layer structure up to T = 400 °C in montmorillonite and up to T = 700 °C in vermiculite. Furthermore, it is evident from EXAFS spectra collected at room temperature that Hg–H2O complexes are present in both montmorillonite and vermiculite, whereas the HgO form appears only in vermiculite.