Synthesis of Fe‐doped chrysotile and characterization of the resulting chrysotile fibers

Abstract

This study describes the formation of Fe-doped chrysotile fibers with partial and total substitution of Mg by Fe. Syntheses were carried out with various starting mixtures (oxides, pure synthetic forsterite) in an externally heated pressure vessel in controlled hydrothermal conditions: temperature, 270 -400 °C; pressure, 0.5 -2 kbar; duration of treatment 160 -480 hours. Pure synthetic forsterite was prepared by the flux growth technique. The starting material and run products were characterized by X-ray powder diffraction (XRPD), scanning and transmission electron microscopies combined with energy-dispersive spectrometry (SEM-EDS and TEM-EDS), differential scanning calorimetry (DSC) and thermogravimetry (TG). Variations observed in abundance and size of Fe-doped chrysotile fibers were attributed to different experimental conditions for their synthesis. However, morphological shape turned out to depend on the starting mixtures used. Since natural samples are often difficult to obtain in a sufficiently pure state, these synthetic and well-characterized Fedoped chrysotile fibers can be used for better understanding of the mechanisms involved in asbestos toxicity, as well as of the role of Fe in diseases induced by asbestos phases. These synthetic Fe-doped chrysotile fibers, together with non-toxicity testing, may also have potential for exploitation in industrial fields.

TG/DSC study of the thermal behaviour of hazardous mineral fibres

“…A sharp exothermic peak at 820 °C indicates the crystallization of forsterite [19,43,44] as confirmed by PXRD data (Fig. 2).…”

“…The endothermic peak observed for the chrysotile UICC shows a shift versus lower temperature (633 °C) with respect to both chrysotile from Val Malenco (652 °C) and chrysotile from Balangero (660 °C). The different temperature of chrysotile decomposition (range 633-660 °C) of the three chrysotile samples may be due to the different fibre size (width and length) distribution and the presence of different amount of Fe [43,49] and Ni [44] substitute for Mg in octahedral sheet [32]. The relationships between distribution size, Ni, Fe content and change of temperature stability of chrysotile are complex.…”

“…The product of the dehydroxylation of chrysotile recrystallized to forsterite [19,43,44] caused a sharp exothermic peak at 823 °C (Fig. 1, Table 3).…”

Multi-Analytical Approach for Identifying Asbestos Minerals In Situ

“…Under these conditions, the data are not quantitative; however, in the first step the presence of Fe, Ni and Mn in serpentinite could suggest both an isomorphous substitution of Mg in the octahedral sites of serpentine minerals [51,52] and/or the presence of mineral impurities combined with serpentine minerals (e.g., chlorite, magnetite). Other elements are also detected in serpentine minerals such as Ti, Cr, (Figure 4), which represent an almost exclusively isomorphous substitution of Mg [53].…”

Redistribution of Mg and Ni cations in crystal lattice of conical nanotube with chrysotile structure

“…Since the middle of 20th century, various research groups have focused on synthesis of pure Mg-chrysotile [38][39][40][41], and related Fe [42,43], Co [44], Ni-doped [45][46][47][48][49] structural analogs. The principal goal of recent studies in this field was to reveal pre-nucleus states that take part in the nanotube formation, and determine the role of their structure in the nanotube formation process.…”