کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8910815 | 1637930 | 2018 | 16 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Effect of aqueous Si/Mg ratio and pH on the nucleation and growth of sepiolite at 25â¯Â°C
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The proposed reaction path for the formation of sepiolite is based on the temporal evolution of the chemical compositions of the experimental solution and solids: (i) Nucleation and growth of Al-sepiolite occurred during the first 8â¯days of the experimental runs via condensation and polymerization of SiOH tetrahedra onto Mg-Al-O-OH template sheets at a precipitation rate of â¼2.19â¯Â±â¯0.01â¯Ãâ¯10â10â¯molâ¯sâ1. (ii) At decreasing pH and in the absence of [Al]aq this intermediate phase transformed into aluminous sepiolite at a slower crystal growth rate of â¼1.08â¯Â±â¯0.02â¯Ãâ¯10â12â¯molâ¯sâ1. This finding explains the high abundances of sepiolite in highly alkaline, evaporitic, lacustrine and soil environments, where the growth rates of sepiolite are considered faster (10â11 to 10â10â¯molâ¯sâ1, Brady, 1992). We propose that (i) low rates of Mg2+ ion dehydration and silica condensation and polymerization at the surface of the initial precipitate, (ii) the formation of MgS040 aquo-complexes and (iii) the reduced sorption rates of [Si]aq and [Mg]aq at the active growth sites on sepiolite surfaces at pHâ¯â¤â¯8.3 retard the precipitation of sepiolite in marine-diagenetic environments.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geochimica et Cosmochimica Acta - Volume 227, 15 April 2018, Pages 211-226
Journal: Geochimica et Cosmochimica Acta - Volume 227, 15 April 2018, Pages 211-226
نویسندگان
Andre Baldermann, Vasileios Mavromatis, Paula M. Frick, Martin Dietzel,