Siliceous resources play a major role in CO₂ conversion, mineralization, and storage which is crucial for a sustainable energy transition. For example, several gigatons of CO₂ emissions can be reliably converted to solid carbonates on reaction with earth-abundant Ca- and Mg-bearing silicates. Siliceous resources such as olivine are hosts to energy critical metals such as nickel, while shales are hosts to vanadium. Despite the crucial role played by siliceous resources in the energy transition, there is a limited understanding of the interactions of siliceous resources in acidic environments. Interactions of siliceous interfaces with acidic solutions are known to leach metals into solution. However, uncertainties associated with the coordination of siliceous interfaces, dissolution, and reprecipitation of siliceous phases remain poorly constrained. With this context, two case studies are discussed. The first involves the carbon mineralization of Ca- silicate interfaces. Carbon mineralization of Ca- silicates occurs via the release of Ca²⁺ ions into the solution, formation of sodium silicate in the bulk solution or silicon dioxide. These insights are captured using experiments on architected materials and molecular scale modeling using ReaxFF force fields. The second involves the chemical and morphological evolution of shales in acidic environments. Clay and carbonate phases impact silica dissolution. Total porosity of shales increases initially due to the dissolution of carbonate and clay phases and is followed by a decrease in porosity to the reprecipitation of SiO₂. These non-monotonic changes in the micron-scale porosity of silica rich – carbonate/clay lean are noted using in-situ X-ray microtomography experiments. The changes in the amorphous and crystalline content of siliceous phases due to dissolution and reprecipitation alter the porosity and fluid flow paths.

Nabankur Dasgupta

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