Iron exchanged natural mordenite: UV–Vis diffuse reflectance and Mössbauer spectroscopy characterisation

Purified natural mordenite (ZP) from Palmarito de Cauto deposit, Cuba, was modified with Fe2+ and Fe3+ cations through ion-exchange in acid medium and characterised by UV–Vis diffuse reflectance, FTIR and Mössbauer spectroscopies. Fe2+ exchange is less favoured than Fe3+ exchange, which may be due to higher Fe3+ valence. In the Fe2+ exchanged samples, Fe2+ZP, all incorporated Fe2+ is found in octahedral coordination and it should be mainly in cationic extra-framework positions inside mordenite channels as a charge compensating cation. In the case of the Fe3+ exchanged samples, Fe3+ZP, the incorporated Fe3+ is present in both octahedral and tetrahedral coordination and it can be in both cationic extra-frameworks positions as a charge compensating cation and in form of oxy-hydroxides originated by Fe3+ hydrolysis.