کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9529227 | 1637793 | 2005 | 18 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Dissolution at the surface of jarosite: an in situ AFM study
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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چکیده انگلیسی
The development of the morphology of the rhombohedral {012} faces of jarosite [(K,H3O)Fe3(SO4)2(OH)6] has been observed in situ at the molecular scale in aqueous dissolution experiments using atomic force microscopy (AFM). Synthetically grown rhombohedral surfaces show growth spirals with monolayer steps about 0.5 nm high, corresponding to the d values of the (012) plane. Monolayer-deep etch pits formed on surface terraces during dissolution. The formation and expansion of these etch pits seem to contribute more to the overall dissolution than the retreat of steps that bound terraces. This observation indicates that the dissolution mechanism of jarosite is controlled by surface structure and differs from the step retreat typical for most minerals for which dissolution mechanisms at a molecular level have been investigated. In aqueous solution at pH 5.5, formation of thin, soft overlayers on the jarosite is observed. By adding Na2-EDTA, these overlayers are removed and dissolution takes place mainly by the formation and growth of etch pits. To investigate the influence of H3O+ substitution on the dissolution kinetics, K-dominant jarosite was compared with hydronium jarosite [(H3O)Fe3(SO4)2(OH)6]. Dissolution rates calculated in situ by measuring the vertical position of the surface vs. time on hydronium- and K-dominant jarosite {012} faces in deionized water are 4.41±0.7Ã10â7 and 1.45±0.98Ã10â7 mol mâ2 sâ1, respectively, confirming that H3O+ content on the A site in the structure accelerates jarosite dissolution.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 215, Issues 1â4, 15 February 2005, Pages 499-516
Journal: Chemical Geology - Volume 215, Issues 1â4, 15 February 2005, Pages 499-516
نویسندگان
Biliana Gasharova, Jörg Göttlicher, Udo Becker,