Spectroscopic investigations on structural incorporation pathways of FeIII into zeolite frameworks in cement-relevant environments

Fe-III-containing aluminosilicate zeolites are present in cement-relevant and natural environments. Although Fe-III is known to occur in framework tetrahedral sites where it substitutes isomorphically (AlO4)-O-III or in extra-framework octahedral sites as free Fe(H2O)(6)(3+), the structural incorporation process of Fe-III into different sites is little known. We aim to discern feasible pathways of Fe-III incorporation using hydrothermal synthesis methods and synchrotron-based spectroscopic analyses. Results showed that introducing either Fe3+ or Fe2O3 center dot xH(2)O initially during zeolite nucleation did not lead to Fe-III incorporation into the zeolites but only Fe2O3 center dot xH(2)O prevailed in both cases. However, Fe(NO3)(3), FeCl3, and Fe2O3 center dot xH(2)O affected the kind of zeolite formed. A feasible pathway to incorporate tetrahedral Fe-III in the zeolite framework was to introduce firstly Fe-III in the cage of faujasite-Y followed by a phase transformation to chabazite. This study facilitates understanding of Fe-III uptake in zeolites and of Fe-III functional sites that can contribute to immobilization of contaminants.

Automated summary

The study found that introducing Fe3+ ions or iron oxide during zeolite nucleation does not result in Fe-III incorporation into the zeolites, but different forms of Fe-III can affect the type of zeolite formed. Introducing Fe-III into the cage of faujasite-Y, followed by a phase transformation to chabazite, provides a feasible pathway for incorporating tetrahedral Fe-III into the zeolite framework.