DOLOMITE SURFACE SPECIATION AND REACTIVITY IN AQUATIC SYSTEMS - RATES DEPEND ON SURFACE SPECIATION
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dc.contributor.author | Pokrovsky O.S. | |
dc.contributor.author | Schott J. | |
dc.contributor.author | Thomas F. | |
dc.date.accessioned | 2021-01-09T06:24:22Z | |
dc.date.available | 2021-01-09T06:24:22Z | |
dc.date.issued | 1999 | |
dc.identifier | https://elibrary.ru/item.asp?id=184850 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 1999, , 19, 3133-3143 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/22515 | |
dc.description.abstract | The surface charge of dolomite (CaMg(CO3)2) was measured as a function of pH (6.5-11.5), pCO2 (10-3.5, 0.01, and 0.96 atm) and ionic strength (0.01, 0.1, and 0.5 M NaCl) using potentiometric titrations in a limited residence time reactor. Dolomite zeta potential (ζ) was determined using streaming potential and electrophoresis techniques at pH 2 to 12 in solutions having ionic strengths from 0.001 to 0.1 M NaCl as a function of aqueous Ca2+, Mg2+, and CO32- concentrations. The point of zero charge (PZC) and isoelectric point (IEP) of dolomite are the same (pH ~8 at pCO2 ~10-3.5 atm) and very close to those of calcite and magnesite. On the basis of these results, a surface complexation model (SCM) is proposed that postulates the presence of three distinct primary hydration sites: >CO3H°, >CaOH°, and >MgOH°. The intrinsic stability constants of dolomite surface reactions were determined by fitting the pH dependence of the surface charge and taking into account the isoelectric points and ζ-potential values for a wide range of solution compositions. In most natural aquatic environments, dolomite surface speciation can be modeled using the following species: >CO3-, >CO3Me+, >MeOH2+, >MeHCO3°, and >MeCO3-, where Me = Ca, Mg. The speciation model presented in this study allows description of metal and ligand adsorption onto dolomite surface and provides new insights on the mechanisms that control dolomite dissolution/crystallization in aqueous solutions. In particular, it is shown that dolomite dissolution is controlled by the protonation of >CO3H° surface complexes at pH < 6 and by hydrolysis of >MeOH2+ groups at higher pH. | |
dc.title | DOLOMITE SURFACE SPECIATION AND REACTIVITY IN AQUATIC SYSTEMS - RATES DEPEND ON SURFACE SPECIATION | |
dc.type | Статья |
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