A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly

Abstract

The exposure of humans to erionite fibres of appropriate morphology and dimension has been unambiguously linked to the occurrence of Malignant Mesothelioma. For this reason, a detailed morpho-structural investigation through Electron Microscopy techniques has been performed on erionite samples collected at two different localities, Durkee (ED) and Rome (ER), Oregon, USA. The sample from Rome has been also investigated after a prolonged leaching with Gamble’s solution (ER4G) in order to evaluate the possible occurrence of morpho-structural modifications induced by this Simulated-Lung-Fluid (SLF). Here we report how the micrometric erionite fibres evolve in irregular ribbon- or rod-like bundles as a function of different nano-structural features. The reasons for the observed morphological variability have been explained by considering the structural defects located at ED surface fibrils (bi-dimensional ribbons) and the presence of nontronite, an iron-bearing clay mineral embedding the ER fibrils (mono-dimensional rods). ER4G shows a decrease in width of the rod-like fibres due to their partial digestion by SLF leaching, which synchronously dissolves nontronite. The reported results represent a valuable background toward the full comprehension of the morphological mechanisms responsible for potentially damage of lung tissue through the potential relocation of fibers to extrapulmonary sites, increasing the carcinogenic risk to humans.

Where is iron in erionite? A multidisciplinary study on fibrous erionite-Na from Jersey (Nevada, USA)

“…Nontronite also explains the minor amount of Mg detected by the chemical analysis of the sample. The presence of nontronite as clay impurity in fibrous erionite samples has been already reported29. Hence, with the results of our study we have verified that the very same erionite sample may contain different iron-bearing impurities, explaining why different authors see impurities of different kind in natural fibrous erionite.…”

“…Later, Matassa et al 29. discovered that the same erionite-K from Rome actually contains aggregates of nontronite, an iron-bearing smectite of ideal formula (Ca 0.5 , Na) 0.33 Fe 3+ 2 (Si 3.67 Al 0.33 )O 10 (OH) 2 ·nH 2 O. Successive EDX analysis of the fibres leached with simulated lung fluids (SLF) indicated the absence of iron due to the removal of nontronite from their surface produced by the leaching process, confirming the absence of iron in the structure of erionite.…”

Thermal Stability of Woolly Erionite-K and Considerations about the Heat-Induced Behaviour of the Erionite Group

“…18 nm has been calculated for r a throughout the investigated thermal range. This value is of the same order of magnitude of the diameter of a single fibril of woolly erionite-Na, observed from TEM images by Matassa et al [33], that is characterized by a similar morphology. A reduction of r a is observed as T break approaches.…”

“…Moreover, woolly erionite-K has a significantly higher volume of mesopores of 0.125 cm 3 /g with respect to 0.021 cm 3 /g of fibrous erionite-Na. The mesoporosity arises from the peculiar self-assembly of woolly erionite consisting of bi-dimensional ribbons [33]. The large external surface, coupled to the absence of significant reduction of the s.s. at OW sites for T < 348 K, suggests the release of water, estimated to be ca.…”

Prismatic to Asbestiform Offretite from Northern Italy: Occurrence, Morphology and Crystal-Chemistry of a New Potentially Hazardous Zeolite

“…The main mode observed in the offretite fibers of MB2287 is 20-25 µm, and~93% of the measured fibers are >5 µm, and therefore they may also be significantly associated with carcinogenesis when breathed in term of lengths [3,10,19]. About the physical features, particular attention also needs to be paid to reliably evaluating the toxicological effects related not only to the dimension of offretite fibers, but also to their flexibility and their tendency to split, features that may significantly modify their surface area and, consequently, their reactivity [18,79]. The various offretite samples show different mechanical behavior, having an extremely fibrous with flexible to rigid appearance or forming prismatic to acicular, brittle crystals.…”