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Title: Determination of mineral dissolution regimes using flow-through time-resolved analysis (FT-TRA) and numerical simulation

Flow-through time resolved analysis (FT-TRA) involves subjecting small mineral samples (< 10 mg) inserted in a miniature flow-through cell (50 μL) to controlled flows of eluent analyzed on-line by ICP-MS. In this study, FT-TRA is used to empirically determine the dissolution regimes for the two well-studied minerals forsterite and calcite, representing minerals with relatively slow and fast dissolution kinetics. A proportional increase in steady-state effluent [Mg, Si] concentrations with increasing flow-through cell eluent residence times confirms a dominantly surface-controlled dissolution regime for a powdered forsterite sample at pH 2.3, implying that transport limitations are negligible. In contrast, the relationship between flow rates and dissolution rates for single grain calcite samples at pH 2.3-4 reveals that transport limitations affect the rate of calcite dissolution. In order to provide a quantitative and process-based assessment of the effect of diffusive transport limitations, simulations of the calcite experiments were performed with a high resolution, pore-scale model that considers the geometry of the calcite grain and the FT-TRA flow-through reactor. The pore-scale model reproduces the observed effluent [Ca] concentrations for all experimental conditions using a single set of surface kinetic parameters, by accounting for the formation of a diffusive boundary layer (DBL) that varies inmore » thickness as a function of flow rates. These results demonstrate that combining FT-TRA with pore-scale modeling makes it possible to obtain unprecedented insights not achievable by either method separately, including quantification of DBL thicknesses and the determination of transport controls as a function of pH, flow velocity and residence times.« less
Authors:
ORCiD logo [1] ;  [2] ;  [1] ;  [1]
  1. Univ. of British Columbia, Vancouver, BC (Canada). Dept. of Earth, Ocean and Atmospheric Sciences
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth and Environmental Sciences
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 430; Journal Issue: C; Related Information: © 2016 Elsevier B.V.; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Dissolution regime; Flow-through; Mineral dissolution; Dissolution rates; Forsterite dissolution; Calcite dissolution
OSTI Identifier:
1474951
Alternate Identifier(s):
OSTI ID: 1358933