Transport and aggregation of particles near a dissolving mineral: microfluidic experiments
E001
Abstract
This final year project aims to enhance the effectiveness of geological barriers used as gas reservoirs. The study focuses on diffusiophoresis, a colloidal transport mechanism induced by a con centration gradient. It acts as an inhibitor of the dissolution of calcite, a mineral that is abundant in these systems. In the first phase, microfluidic experiments were carried out to reproduce the results found in the literature, by injecting negatively charged particles (sulfates and/or carboxylates) into a microchannel containing dissolved calcite. The observations revealed the formation of a passivation layer, which was irreversible in the case of sulfate-coated particles. This layer was then characterised by Raman spectroscopy and XRD, leading to a new question: identifying the source of this irreversibility. Two hypotheses were explored. One involved local gypsum precipitation, tested by modelling and experimentation; the other involved interactions between particles, interpreted using DLVO theory and supplemented by simulations. This work highlights the mechanisms behind irreversible passivation layers and confirms the value of diffusiophoresis in limiting mineral dissolution in porous media.