• Probing electrolytes’ impact on interfacial layers that influence olivine dissolution

Olivine (magnesium iron silicate) is a prime contender for CO2 mineralization in aqueous environments via natural weathering or industrial processes. However, upon its dissolution a silica-rich alteration layer (SAL) gets formed, which can drastically slow down the chemical reactions at the mineral-electrolyte interface. Despite extensive research, the SAL’s nature and variability remain to be clarified. SAL porosity, thickness and chemical composition all play a role and can evolve. Sulfuric acid is known to expedite olivine dissolution. However, there is conflicting evidence regarding the role of iron oxidation in the passivation of SALs.
To get more insight into Olivine SALs, we used Confocal Raman, Scanning Electron, and Fluorescence Liftetime Imaging Microscopies. We monitored the dissolution kinetics and interfacial layer formation in sulfuric, hydrochloric, and nitric acid at varying pH levels. Our findings underscore the significant influence of electrolyte chemistry on the interfacial layer's formation, composition and growth.
A comprehensive understanding of the layer formation holds the potential to yield invaluable insights into olivine weathering kinetics, thereby paving the way for enhanced olivine-based CCS strategies.