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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/12865

Title: In situ atomic force microscopy measurements of biotite basal plane reactivity in the presence of oxalic acid
Authors: Haward, Simon J.
SMITS, Mark
Ragnarsdottir, Kristin Vala
Leake, Jonathan R.
Banwart, Steven A.
McMaster, Terence J.
Issue Date: 2011
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Citation: GEOCHIMICA ET COSMOCHIMICA ACTA, 75(22), p. 6870-6881
Abstract: We have used a direct imaging technique, in situ atomic force microscopy (AFM), to observe the dissolution of the basal biotite surface by oxalic acid over a range of temperatures close to ambient conditions, using a specially designed AFM liquid cell and non-invasive intermittent contact mode of operation. From the 3-dimensional nanometre-resolution data sets, we observe a process characterised by the slow formation of shallow etch pits in the (001) surface and fast growth of etch pits from the resulting steps, which represent proxies for the {h k 0} surface. Measurements of dissolution rates as a function of temperature allow a determination of an apparent activation energy (E(a, app)) for the process, via mass-loss calculations from image analysis. We obtain a value of E(a, app) = 49 +/- 2 kJ mol(-1), which is consistent with separate calculations based on planar area etch pit growth, and measurements of etch pit perimeters, indicating that this value of E(a, app) is representative of {h k 0} surface dissolution. The measurement of etch pit perimeters also enables an estimation of apparent activation energy as a function of step density indicating substantially higher apparent activation energy, up to E(a, app) = 140 kJ mol(-1), on extrapolation towards a pristine surface with no defects. We suggest that this higher value of E(a, app) represents the slow formation of etch pits into the (0 0 1) surface. (C) 2011 Elsevier Ltd. All rights reserved.
Notes: [Haward, SJ] MIT, Dept Mech Engn, Cambridge, MA 02139 USA. [Haward, SJ; McMaster, TJ] Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England. [Haward, SJ; Ragnarsdottir, KV] Univ Bristol, Dept Earth Sci, Bristol BS8 1RJ, Avon, England. [Smits, MM; Leake, JR] Univ Sheffield, Dept Anim & Plant Sci, Sheffield S10 2TN, S Yorkshire, England. [Banwart, SA] Univ Sheffield, Kroto Res Inst, Dept Civil & Struct Engn, Sheffield S3 7HQ, S Yorkshire, England. [Smits, MM] Hasselt Univ, Ctr Environm Sci, B-3590 Diepenbeek, Belgium. [Ragnarsdottir, KV] Univ Iceland, Inst Earth Sci, Sch Engn & Nat Sci, IS-101 Reykjavik, Iceland. shaward@mit.edu
URI: http://hdl.handle.net/1942/12865
DOI: 10.1016/j.gca.2011.09.010
ISI #: 000296579600009
ISSN: 0016-7037
Category: A1
Type: Journal Contribution
Validation: ecoom, 2012
Appears in Collections: Research publications

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