Characterisation of potentially toxic natural fibrous zeolites by means of electron paramagnetic resonance spectroscopy and morphological-mineralogical studies. (March 2022) - Giordani, Matteo
Abstract: This study explored the morphological, mineralogical, and physico-chemical features of carcinogenic erionite and other possibly hazardous zeolites, such as mesolite and thomsonite, while also investigating the interacting capability of the mineral surface at the liquid/solid interface. Extremely fibrous erionite is K + and Ca 2+ -rich and shows the highest Si/Al ratio (3.38) and specific surface area (8.14 m 2 /g). Fibrous mesolite is Na + and Ca 2+ -rich and displays both a lower Si/Al ratio (1.56) and a smaller specific surface area (1.56 m 2 /g). The thomsonite composition shows the lowest values of Si/Al ratio (1.23) and specific surface area (0.38 m 2 /g). Electron paramagnetic resonance data from selected spin probes reveal that erionite has a homogeneous site distribution and interacts well with all spin probes. The surfaces of mesolite and thomsonite are less homogeneous and closer polar sites were found through consequent interaction with the probes. The mesolite surface can also clearly interact but with a lower strength and may represent a potential health hazard for humans, though with a lower degree if compared to erionite. The thomsonite surface is not inert and interacts with the probes with a low-grade capability. We can expect small fragments of thomsonite to interact with the biological environment, though with a low-grade intensity. Graphical abstract: Image 1 Highlights: EPR was crucial to understand the surface properties and interacting capabilities. Erionite showed the highest interaction and adsorbed percentages of probes. Mesolite was interacting at close sites, representing a potential health hazard. Thomsonite interacted less strongly, but cannot be considered a safe zeolite. The surface properties are useful in the assessment of the potential toxicity.