A novel in-situ Raman spectroscopic cell for aqueous geochemistry at the solid-liquid interface

In-situ Raman spectroscopy has the potential to be a powerful technique for monitoring geochemical reactions at a solid-liquid interface in real time. In this article, we present the development and testing of an in-situ Raman spectroscopic cell, which can be used for reaction systems at moderate temperatures and pressure [<1000 psi (6.89 MPa), <100 °C, relevant to subsurface geologic systems] and can hold samples large enough for chemical mapping of heterogeneous rock surfaces. The system is validated by measuring the temperature-dependent conversion of gypsum to calcite over time. Near total conversion of gypsum to calcite on the mineral surface took 29 hours at room temperature and 150 minutes at 100 °C, corresponding to an 11.6-fold increase in the conversion rate. We anticipate that this cell can be an important tool in quantifying the rates of carbon mineralization relevant to geologic carbon sequestration, particularly for the elevated rates recently observed in mafic/ultramafic rocks.