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An XPS study of the dissolution kinetics of chrysotile in 0.1 N oxalic acid at different temperatures |
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| Authors: | J H Thomassin J Goni P Baillif J C Touray M C Jaurand |
| Institution: | 1. E.R.A., C.N.R.S. No 601, Département des Sciences de la Terre, Université d'Orléans, 45045, Orléans Cédex, France 2. Service géologique national (B.R.G.M.), B.P. No 6009, 45018, Orléans Cédex, France 3. Laboratoire de biopathologie pulmonaire, C.H.U., Henri Mondor, Avenue du Maréchal de Lattre de Tassigny, 94010, Créteil, France |
| Abstract: | The dissolution of chrysotile is studied in regard to the surfaces analysis by photoelectron spectrometry. After leaching of chrysotile (Provenance: Thetford; about 200 mg of fibers of 1 cm length) in nonstirred 0.1 N oxalic conditions, the composition of the mineral surfaces is determined by XPS; kinetic curves of dissolution are given in the range 22–80°C. Two conditions for the rate-limiting step are involved for the explanation of the dissolution: diffusion of Mg2+ through the fibrous gel or dissociation of chrysotile. By the former, some values of the diffusion coefficient are proposed: D varies from 5·10?19 cm2s?1 to 5·10?16 cm2s?1, in the range 22–80°C. By the second model, the leaching rate is estimated from 3 Å (22°C) per h to 250 Å (80°C) per h. For the 2 models, the activation heat energy is in the range 15–20 Kcal. |
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