Effects of Dry Grinding and Leaching on the Crystal Structure of Chrysotile

Suquet, H.

doi:10.1346/ccmn.1989.0370507

Cited by 91 publications

(58 citation statements)

References 17 publications

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“…The DRIFTS absorption bands at 3000-3500 cmand at 1635 cm -x are attributed to the stretching and bending vibration of water and are especially strong for $3 and $4, which implies that water is bound to silica in the chrysotile structure (Suquet, 1989). The absorption bands are especially strong in 100% leached samples and assigned to water adsorbed on Si-OH groups.…”

Section: Generalmentioning

confidence: 95%

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Titulaer

1993

Clays and clay miner.

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Abstract--The maximum crystal radius R. of ice in hollow wet chrysotile tubes is established by thermoporometry to be between 2.8 and 3.2 nm, and the internal pore volume Vn of the tubes to be between 0.008 and 0.02 ml/g. The hollow tubes of chrysotile and, for comparative reasons, small plates of talc, are hydrothermally synthesized at temperatures between 563 and 600 K and at pressures between 75 and 120 hPa. Size and shape of the pores can be varied by changing the Mg/Si molar ratios in steps of 3/1.5 and 3/2 for chrysotile and 3/3.6 and 3/4 for talc. The tubular morphology of the aggregates dried at 393 K is investigated by 1) transmission electron microscopy (TEM), 2) nitrogen adsorption and desorption at 77 K, and 3) diffuse reflectance infrared fourier transformed spectroscopy (DRIFTS). The radius within the hollow tubes, R~, is between 2.5 and 4.0 nm as measured by TEM, and between 2.8 and 3.2 nm as determined by nitrogen adsorption and desorption. The measured radii agree well with the value calculated from crystallographic data, which is smaller than 5.3 nm. Within the dried aggregates the tubes are clustered in regular patterns, in which each tube is surrounded by six other tubes. The external radius, Ro, between the clustered tubes is from 1.6 to 2.9 nm as observed by TEM, and from 1.8 to 2.3 nm by Nz adsorption and desorption. The external radius is not measured by thermoporometry. Where thermoporometry only measures the average pore size and pore volume within the tubes, TEM and N2 adsorption and desorption additionally provide the corresponding values between the tubes. A third pore radius, 5 to 20 nm between the clusters of chrysotile tubes, is established with N2 adsorption and desorption.

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Section: Generalmentioning

confidence: 95%

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Titulaer

1993

Clays and clay miner.

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“…The L1 spectrum is similar to that of a pure silica sample such as Aerosil 380. As shown by Suquet (1989), IR spectroscopy is a very sensitive method for detecting the destruction of the crystalline structure of silicates whether by grinding or leaching.…”

Section: Ir Spectroscopymentioning

confidence: 99%

Preparation of porous materials by chemical activation of the Llano vermiculite

et al. 1991

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A B S T R A C T:A mild acid attack of the Llano vermiculite produces porous materials suitable for use as cracking catalysts and/or catalysts supports. After HCI attack at 80~ (1 M), the number of acid sites measured by the Hammett indicator method is ~0.50/nm 2, and the specific surfaces are 245 m2/g after calcination at 550~ (4 h), and 55 m2/g after steaming at 750~ (4 h). The performance of leached (1 M HCI) vermiculite has been compared with another hydrocarbon cracking catalysty-AI203. The leached vermiculite produces a definite higher conversion and higher C3, C4 and gasoline yields, but much lower coke production. By electron microscopy, infrared spectroscopy, X-ray powder diffraction and thermal analysis, it has been shown that the leached vermiculite samples are composed of more or less attacked layers retaining their original platy morphology, and non-crystalline hydrated silica. Chemical analyses indicate that octahedral cations are dissolved first.

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“…In particular, mechano-chemical treatment, which could be used for disposing of and/or recycling asbestos, is capable of increasing particle reactivity [33], reducing the sintering temperature [34] and reducing the thermal decomposition temperature [35,36]. In this regard, Suquet [37] has shown that grinding and/or leaching pre-treatment of chrysotile affected its dissolution in water. A mechano-chemical treatment was also successfully applied to asbestos by Plescia et al [38], who showed how grinding can completely modify the fibrous morphology of asbestos.…”

Section: Introductionmentioning

confidence: 99%

Effect of Grinding on Chrysotile, Amosite and Crocidolite and Implications for Thermal Treatment

2018

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Nowadays, due to the adverse health effects associated with exposure to asbestos, its inertization is one of the most important issues of waste risk management. Based on the research line of mechano-chemical and thermal treatment of asbestos containing materials, the aim of this study was to examine the effects of dry grinding on the structure, temperature stability and fibre size of chrysotile from Balangero (Italy), as well as standard UICC (Union for International Cancer Control) amosite and standard UICC (Union for International Cancer Control) crocidolite. Dry grinding was accomplished in an eccentric vibration mill by varying the grinding time (30 s, 5 and 10 min). Results show a decrease in crystallinity, the formation of lattice defects and size reduction with progressive formation of agglomerates in the samples after the mechanical treatment. Transmission electron microscopy (TEM) results show that the final product obtained after 10 min of grinding is composed of non-crystalline particles and a minor residue of crystalline fibres that are not regulated because they do not meet the size criteria for a regulated fibre. Grinding results in a decrease of temperature and enthalpy of dehydroxylation (∆H dehy ) of chrysotile, amosite and crocidolite. This permits us to completely destroy these fibres in thermal inertization processes using a lower net thermal energy than that used for the raw samples.

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Effects of Dry Grinding and Leaching on the Crystal Structure of Chrysotile

Cited by 91 publications

References 17 publications

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Characterization of Tubular Chrysotile by Thermoporometry, Nitrogen Sorption, Drifts, and TEM

Preparation of porous materials by chemical activation of the Llano vermiculite

Effect of Grinding on Chrysotile, Amosite and Crocidolite and Implications for Thermal Treatment

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