Transport of environmentally relevant particles in non-transparent soil-like porous structures – TRANSOIL

The physical understanding of particle transport within liquid-saturated porous media is a prerequisite in many environmental and industrial fields, such as transport in soil, aquifers, petroleum rocks, building materials and catalysts. Currently the leading field for tracking particle dynamics in model solid porous media is based on optical microscopy techniques, which require optically transparent samples. Our objective is to follow the movement of particles, down to the colloidal size, inside a non-transparent porous matrix, akin to natural porous matrices such as soil. We intend to use the latest developments in X-ray based techniques, both in the real and reciprocal space, X-ray imaging and X-ray photon correlation spectroscopy. Complexity of the system is developed along two lines: (a) nature of the mobile particles (size, density, passive/active particle), which decides the balance between directional motion (such as gravitation-induced sedimentation) and stochastic motion of the particles (Brownian motion) and (b) nature of the confining matrix, especially in terms of varying structural anisotropy of the confining matrix introduced via a clay component (model soils). The first part of the project consists of methodological developments, especially those related to a novel analysis of image sequences yielding the intermediate scattering function (ISF). We regard ISF as a central physical quantity, where real and reciprocal space techniques can meet. The second part of the project explores particle mobility in non-transparent matrices going in the direction of model soils. A third, parallel exploratory part deals with active particles, for which there are several similarities with sedimenting particles, in terms of ISF analysis.