Chemical studies of amphibole asbestos. I. Structural changes of heat-treated crocidolite, amosite, and tremolite from infrared absorption studies

Abstract

The thermal dehydroxylation, oxidation, and decomposition of the amphiboles: crocidolite, amosite, and tremolite have been investigated with infrared spectroscopy. Changes in the spectra with temperature have been related to these processes. The dehydroxylation of crocidolite and amosite in air causes only small structural rearrangements but dehydration of tremolite occurs at higher temperatures during decomposition of the amphibole structure. For both crocidolite and amosite the temperature of dehydroxylation is higher and the decomposition temperature lower in vacuum than in air. These differences are discussed in terms of variation in chemical composition and changes in the mechanism of dehydroxylation. For crocidolite it is suggested that certain hydroxyl groups are removed preferentially.    Small structural rearrangements associated with oxidation and dehydroxylation cause a broadening and shifting of the main absorption bands but decomposition of the structure produces marked changes in the spectra.