Iron exchanged natural mordenite: UV-Vis diffuse reflectance and Mossbauer 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 Mossbauer 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.