FORSTERITE SURFACE COMPOSITION IN AQUEOUS SOLUTIONS: A COMBINED POTENTIOMETRIC, ELECTROKINETIC, AND SPECTROSCOPIC APPROACH
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dc.contributor.author | Pokrovsky O.S. | |
dc.contributor.author | Schott J. | |
dc.date.accessioned | 2021-01-24T07:27:40Z | |
dc.date.available | 2021-01-24T07:27:40Z | |
dc.date.issued | 2000 | |
dc.identifier | https://elibrary.ru/item.asp?id=414381 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 2000, 64, 19, 3299-3312 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/23663 | |
dc.description.abstract | Surfaces of natural and synthetic forsterite (Fo91 and Fo100) in aqueous solutions at 25°C were investigated using surface titrations in batch and limited residence time reactors, column filtration experiments, electrokinetic measurements (streaming potential and electrophoresis techniques), Diffuse Reflectance Infrared Spectroscopy (DRIFT), and X-ray Photoelectron Spectroscopy (XPS). At pH < 9, a Mg-depleted, Si-rich layer (<20 #9 thick) is formed on the forsterite surface due to a mg2+ # H+ exchange reaction. Electrokinetic measurements yield a pHIEP value of 4.5 corresponding to the dominance of SiO2 in the surface layer at pH < 9. In contrast, surface titrations of fresh powders give an apparent pHPZC of about 10 with the development of a large positive charge (up to 10-4 mol/m2 or 10 C/m2) in the acid pH region. This may be explained by penetration of H+ into the first unit cells of forsterite surface. The surface charge of acid-reacted forsterite is one or two orders of magnitude lower than that of unreacted forsterite with an apparent pHPZC at around 6.5 and a pHIEP value of 2.1 which is close to that for amorphous silica and reflects the formation of a silica-rich layer on the surface. XPS analyses indicate the penetration of hydrogen into the surface and the polymerization of silica tetrahedra in this leached layer. At pH > 10, a Si-deficient, Mg-rich surface layer is formed as shown by XPS analyses and the preferential Si release from the surface during column filtration experiments. | |
dc.title | FORSTERITE SURFACE COMPOSITION IN AQUEOUS SOLUTIONS: A COMBINED POTENTIOMETRIC, ELECTROKINETIC, AND SPECTROSCOPIC APPROACH | |
dc.type | Статья |
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