Towards a detailed comprehension of the inertisation processes of amphibole asbestos:in situhigh-temperature behaviour of fibrous tremolite

Abstract

Thermal behaviour of fibrous tremolite from Maryland, USA has been investigated in situ up to breakdown temperature. Tremolite can be found both as primary constituent and as contaminant in Asbestos Containing Materials (ACMs). The products of breakdown are subcalcic diopside and calcium-rich clinoenstatite in a 2:1 ratio, traces of hematite plus minor silica-rich amorphous material. Thermal expansion follows a regular trend up to 723 K before the onset of Fe2+ oxidation/OH– deprotonation which is completed at 1023 K. At 923 K the Fe3+ migration starts towards M(1) and the corresponding counter-migration of Mg to M(2) and M(3). At T close to structure breakdown, M(2) shows a significant site-scattering reduction possibly consistent with the occurrence of minor vacancies. In fully oxidised tremolite, Fe3+ is allocated prevalently at M(1) and subordinately at M(3). As it is well-known that M(1), along with M(2), is the most exposed octahedral site at the surface of amphiboles, most of the Fe3+ is available for participating in the Fenton-like reactivity of oxidised tremolite, potentially making it dangerous for human health. This point should be properly taken into account in the evaluation of the safety of thermally decomposed tremolite-containing ACMs, in particular in the case of accidentally incomplete treatments.

In situ high-temperature behaviour of fluor-elbaite: breakdown conditions and products

“…The minor expansion of < Z-O > in the same thermal range is consistent with the smaller increase of the aggregate size of the constituent cation < Z r > than < Y r > caused by double multiplicity of the Z site with respect to Y. A similar behaviour was observed for both Fe-dominant/rich tourmalines (e.g., Filip et al 2012;Bosi et al 2018bBosi et al , 2019b and Fe-bearing amphiboles (Oberti et al 2018;Pacella et al 2020;Ballirano and Pacella 2020).…”

Surface and bulk modifications of amphibole asbestos in mimicked gamble's solution at acidic PH

“…It is worth noting that, according to the absence of iron-bearing accessory phases, as compared to the UICC crocidolite sample, no reflections attributable to lepidocrocite were observed in the T-1 M sample. Modifications of cell parameters and volume are very small and point out to a minor contraction potentially attributable to minor Fe(II) oxidation 26 .…”