Sophie Roman
Associate Professor, University of Orléans (France)
This work explores how tiny particles move and interact during mineral dissolution using microfluidic experiments. We show that concentration gradients naturally created during dissolution can actively drive colloidal particles toward the mineral surface—a process known as diffusiophoresis. As particles accumulate, they can form a layer that slows down further dissolution.
These experiments highlight a promising mechanism that could be used to control or even reverse harmful processes in geological environments. For example, the same forces that contribute to the release of contaminants could be harnessed to guide remediation particles exactly where they are needed.
Dissolution of a grain of calcite without particle injection. The microchannel is 1.5 mm wide and 150 µm deep, a solution of 0.02w/w% HCl is injected at 2 µL/min for 17 h. The video shows the 17 hours of dissolution, the speed is ×3000.
Aggregate growth for acid seeded with carboxyl-coated particles flowing around a dissolving grain of calcite. The microchannel is 1.5 mm wide and 150 µm deep, a solution of 0.02w/w% HCl seeded with carboxyl-coated microparticles is injected at 2 µL/min for 17 h. The video shows the process from t = 130 to t = 970 min, the speed of the video is ×3000 the real-time.
Aggregate growth for acid seeded with sulfate-coated particles flowing around a dissolving grainof calcite. A solution of 0.02w/w% HCl is injected at 2 µL/min seeded with sulfate-coated particles. The video shows the process from t = 0 to t = 141 min. The speed of the video is ×500 real time.
Acid seeded with sulfate-coated particles showing diffusiophoresis around a dissolving grain of calcite with no flow. The video is 4 min after particles suspended in acid solution (pH=2.3) have been put in contact with the dissolving calcite. The speed of the video is ×8 real time. Post-processed images showing the background and calcite in dark.