# Dissolution of a single mineral grain: comparison of microfluidic experiments with pore-scale simulations

Piotr Szymczak, Filip Dutka, Vitaliy Starchenko, Florian Osselin, Silvana Magni, Anthony J. C. Ladd

► To cite this version:

Piotr Szymczak, Filip Dutka, Vitaliy Starchenko, Florian Osselin, Silvana Magni, et al., Dissolution of a single mineral grain: comparison of microfluidic experiments with pore-scale simulations. EGU General Assembly 2020, May 2020, Online, France. 10.5194/egusphere-egu2020-12253. http://hal-03554428

HAL Id: hal-03554428

https://hal.science/hal-03554428

Submitted on 4 Feb 2022

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# Dissolution of a single mineral grain: comparison of microfluidic experiments with pore-scale simulations

Piotr Szymczak<fnref n="1" />, Filip Dutka<fnref n="1" />, Vitaliy Starchenko<fnref n="2" />, Florian Osselin<fnref n="3" />, Silvana Magni<fnref n="1" />,<fnref n="4" />, and Anthony J.C. Ladd<fnref n="5" />

We investigate the dissolution of a single grain of soluble mineral by microfluidic experiments and numerical simulations. The experiments use gypsum cylinders (10 mm radius, 0.5 mm thick) cast from rehydrated CaSO4 hemihydrate. The numerical simulations used a finite-volume discretization of the reactive-transport equations with a mesh that conforms to the evolving shape of the mineral. Using the coefficients for dilute aqueous ions, we overpredict the dissolution rate by about 25%. However, including the Debye-Huckel correction for the ion activity gives a substantial reduction in diffusion across the boundary layer at the dissolving solid surface and brings the simulation time scale into quantitative agreement with experiment.

The asymmetry introduced by the flow causes the initially cylindrical sample to take on a shape resembling one half of a figure eight, with the tip pointing in the downstream direction. The simulations give a near perfect match to the experimental size and shape. We quantify the evolution of the volume of the grain and its surface area, as well as its overall shape as the function of the Peclet number. Next we discuss the differences between the geometric surface area and the reactive surface area of a dissolving grain and explore a potential use of these results to upscale the reactive transport problem and obtain the effective reaction rates in a multi-grain system.

<footnote n="1">¹Faculty of Physics, University of Warsaw, Poland (piotr.szymczak@fuw.edu.pl)</footnote>

<footnote n="2">²Chemical Sciences Division, Oak Ridge National Laboratory, USA</footnote>

<footnote n="3">³Institut des Sciences de la Terre d'Orléans, France</footnote>

<footnote n="4">⁴Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland</footnote>

<footnote n="5">⁵Department of Chemical Engineering, University of Florida, Gainesville, USA</footnote>