کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4574000 1629504 2011 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A Monte Carlo study of interlayer and surface structures of tetraphenylphosphonium-modified Na-montmorillonite
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
A Monte Carlo study of interlayer and surface structures of tetraphenylphosphonium-modified Na-montmorillonite
چکیده انگلیسی

Na-montmorillonite modified with tetraphenylphosphonium (TPP+) chloride has been shown to possess a high sorption capacity for iodide and a high thermal stability. We studied TPP+ arrangements in the interlayer space and on the external surface of Na-montmorillonite using Monte Carlo simulations in order to contribute to an explanation of such unresolved experimental issues as interlayer structure and the origin of excess positive surface charge of this clay. The layer spacing simulated for a monomolecular arrangement of interlayer TPP+ ions, which is characterized by a segregation of organic and inorganic species to the opposite montmorillonite surfaces, was found to show the best agreement with the experiment. The simulations revealed further that the maximum surface coverage of adsorbed TPP+ ions equals the negative charge density of the external montmorillonite surface. This TPP+ adsorption does not lead to a desorption of Na+ ions associated with tetrahedral substitutions in the montmorillonite layer, which explains the experimental observation of the excess positive charge of TPP+-modified montmorillonite.

Graphical AbstractFigure optionsDownload as PowerPoint slideResearch Highlights
► Monofacial arrangement of TPP+ in the interlayer space agrees with experimental data.
► This arrangement results in a single TPP+ layer and a layer spacing of 1.9 nm.
► Maximum TPP+ coverage on the external surface equals the cation exchange capacity.
► Positive surface charge arises on montmorillonite due to only partial desorption of Na+.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geoderma - Volume 169, December 2011, Pages 33–40
نویسندگان
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