Abstract
Modelling of a mineral dissolution front propagation is of interest in a wide range of scientific and engineering fields. The dissolution of minerals often involves complex physico-chemical processes at the solid–liquid interface (at nano-scale), which at the micro-to-meso-scale can be simplified to the problem of continuously moving boundaries. In this work, we studied the diffusion-controlled congruent dissolution of minerals from a meso-scale phase transition perspective. The dynamic evolution of the solid–liquid interface, during the dissolution process, is numerically simulated by employing the Finite Element Method (FEM) and using the phase–field (PF) approach, the latter implemented in the open-source Multiphysics Object Oriented Simulation Environment (MOOSE). The parameterization of the PF numerical approach is discussed in detail and validated against the experimental results for a congruent dissolution case of NaCl (taken from literature) as well as on analytical models for simple geometries. In addition, the effect of the shape of a dissolving mineral particle was analysed, thus demonstrating that the PF approach is suitable for simulating the mesoscopic morphological evolution of arbitrary geometries. Finally, the comparison of the PF method with experimental results demonstrated the importance of the dissolution rate mechanisms, which can be controlled by the interface reaction rate or by the diffusive transport mechanism.
Highlights
Mathematical modelling of the moving-boundary dissolution fronts of minerals is important in a wide range of engineering technologies
By comparing with the results of the analytical method, it is verified that the PF model can accurately handle the dynamic evolution of the general diffusion-controlled phase transformation process; using NaCl as an example, the PF model can successfully simulate the mesoscopic evolution of inorganic non-metallic materials caused by diffusion-controlled dissolution
It is worth mentioning that all the input parameters of the PF model have real physical meaning and are based on the experiments data; an observed discrepancy was related to the dissolution mechanism, which was found to be initially limited by the reaction rate, being slower than the diffusion flux due to the rapid change of solute concentration
Summary
Mathematical modelling of the moving-boundary dissolution fronts of minerals is important in a wide range of engineering technologies. It is of great importance in fields of geochemistry, materials science, hydrometallurgy, etc. Minerals dissolve when exposed to aggressive solution environments and form leached layers of varying density and strength [1]. This in turn affects the mechanical and transport properties of the microstructure which further may be relevant at higher scales, for example when the material (rock, concrete or mortars) has structural applications. The dissolution of Ca(OH) from the concrete matrix is one of the key processes of the durability and self-healing mechanisms [3,4,5]
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