InterPore2025

Multiscale modeling of mineral armoring on the rates of coupled dissolution-precipitation reactions

21 May 2025, 15:05

1h 30m

Poster Presentation (MS25) Advances in Carbon Mineralization: Unveiling Multiscale Geo-processes and Coupled Mechanisms Poster

Speaker

Dr Yuankai Yang (Forschungszentrum Jülich)

Description

Mineral armoring, the formation of tight coatings on primary minerals, occurs in various subsurface systems, such as mineral weathering, CO2 sequestration through serpentine carbonation, and anoxic steel corrosion in nuclear waste disposal facilities. This process involves coupled dissolution-precipitation reactions, where a primary mineral dissolves, and a secondary mineral precipitates on its surface (surface passivation). While it is well-known that armoring reduces dissolution rates, the microscopic mechanisms behind this process are not yet fully understood. To address this, we developed a micro-continuum numerical model based on the Nernst-Planck equation, which considers ion electrostatic effects. Using this model, we studied celestine dissolution followed by barite precipitation, as observed in our earlier experiments [1,2]. Our results showed that nanometer-scale pores, characterized by a focused ion beam (FIB) system and a scanning transmission electron microscope (STEM), within the passivation layer formed during dissolution-precipitation reactions, allow dissolved ions to move through. In addition, the gap layer between the celestine and barite plays the role of a buffer that reduces the concentration of ions to a value that maintains the growth velocity of fronts. Both the porosity and surface charges of the nanoporous barite layer are key factors in mineral armoring. Finally, through extensive simulations, we identified two dimensionless parameters that control passivation and its effects on further mineral reactions. The mechanism proposed in our study provides valuable insights into understanding mineral armoring.