Mineral Dissolution -Congruent and Incongruent Dissolution-

Abstract

Since mineral dissolution and precipitation are important chemical reactions in geological processes such as metamorphism and hydrothermal alteration, they are considered to be significant for understanding the fundamental mechanisms of Earth scientific phenomena such as volcanic eruptions and earthquakes. The key points in Carbon dioxide Capture and Storage (CCS) and Carbon dioxide Capture, Utilization and Storage (CCUS) technologies can be thought of as the dissolution and precipitation of minerals. This reaction is not only a heterogeneous solid-liquid reaction through the surface layer between a mineral (solid) and water or carbon dioxide (fluid), but also a complex process involving a mixture of physical processes such as adsorption-desorption, chemical reactions, and transfer phenomena (diffusion, advection, etc.) across the interface between the mineral and fluid. When we consider mineral dissolution in terms of stoichiometry, it can be classified into congruent dissolution and incongruent dissolution. Congruent dissolution refers to dissolution that results in dissolved species consistent with the stoichiometry of the host mineral and rock, while incongruent dissolution is dissolution that shows non-stoichiometric behavior.

In many cases, the dissolution of silicate minerals is considered to be an incongruent dissolution. However, it has been suggested that the addition of chelating agents can greatly enhance the dissolution reaction, apparently exhibiting congruent dissolution.

Incongruent dissolution is one of the causes of heterogeneous solid-liquid reactions, but the results may have implications for a wide variety of geochemical processes. On the other hand, the coexistence of chelating substances such as organic acids may accelerate dissolution (weathering), which provides clues to understanding the origin of life and other processes through rock and fluid interactions.