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Simulation of the nucleation and growth of simple clay minerals in weathering processes: The NANOKIN code |
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| Authors: | B Fritz A Clément Y Amal C Noguera |
| Institution: | a Université Louis Pasteur, Centre de Géochimie de la Surface, UMR 7517 CGS, 1 rue Blessig, F-67084 Strasbourg Cedex, France b CNRS/INSU, UMR 7517 CGS, 1 rue Blessig, F-67084 Strasbourg Cedex, France c CNRS, Institut des Nanosciences de Paris, UMR 7588, 140 rue de Lourmel, 75015 Paris, France |
| Abstract: | We present a numerical approach which accounts for nucleation, growth and/or resorption of particles of fixed composition in aqueous solutions, and which involves functionalities suited to the formation of simple clay minerals in weathering processes, such as: formation of non-spherical particles, heterogeneous/homogeneous nucleation, several growth laws, precipitation resulting from the dissolution of primary minerals. The overall model is now embedded into a new numerical code called NANOKIN, in which several optimization procedures have been introduced in order to allow long dynamics to be followed. NANOKIN was applied to the precipitation of Al- bearing minerals from aqueous solutions: halloysite, kaolinite and Ca-montmorillonite. It allowed us to propose a stable scheme for the competitive precipitation of halloysite and kaolinite under two different types of initial conditions: (1) a given initial super-saturation state of the aqueous solution; (2) progressive super-saturation resulting from the kinetic dissolution of the minerals from a granitic rock under weathering conditions. Both yield particle sizes in the micron range, but with distinct crystal size distribution functions. The interplay between kinetic and thermodynamic effects is discussed. |
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