USING SILICATE MINERALS AS MICROMODELS TO ACCESS THE RELATIONSHIP BETWEEN TRANSPORT AND REACTION AT THE PORE SCALE

Sources of discrepancy between field and laboratory measured mineral dissolution rates are not fully resolved despite their significance in terms of interpretation and prediction of chemical processes in natural systems. The effect of transport on dissolution rates at the pore scale is one of the influential factors with a high uncertainty. The relationship between reaction and transport has been investigated using pore scale modeling techniques including pore-network modeling and lattice Boltzmann methods. Although important insight has been gained through those pore scale simulations, direct observational evidence of physically-chemically coupled pore scale behaviour is limited primarily due to experimental difficulties including reproduction of the small (few micrometers) and complex nature of pore networks. In this regard, approaches incorporating microfluidic platforms provide a unique opportunity for investigating the physicochemical behavior of fluid in porous media at the pore scale. Microfluidic devices have been successfully applied for characterizing and visualizing fluid flow behaviour by using non-reactive substrates like glass or PDMS. Here we adapt microfluidic techniques for investigating the chemical reactivity of minerals by using reactive substrates. A near infrared (NIR) femtosecond laser is used to ablate microchannels on the surface of two polished silicate minerals, anorthite and albite. The micromodel is sealed with a PDMS cover. Fluid flow and mineral dissolution reaction through the micromodel is visualized using fluorescence beads and pH indicator solution, respectively. We are expecting this research to (1) provide direct experimental evidence of coupled reactive transport at the pore scale and (2) improve applicability of lab measured mineral dissolution rate to field scale.