DIPHORES · Pore-scale simulations to study the interaction of DIffusioPHORESis, flow and transport through porous media

Pore-scale simulations to study the interaction of DIffusioPHORESis, flow and transport through porous media

The problem addressed in the project DIPHORES: In several natural and engineered scenarios, the presence of local salt concentration gradients can induce particle migration along the direction of the salt gradient via a physicochemical phenomenon known as diffusiophoresis. This can impact the macroscopic fate and transport of particles through porous media. The key challenge is to understand the interplay between diffusiophoresis and flow and transport through porous media. In project DIPHORES, we have addressed this problem by performing pore-scale simulations and theoretical modelling based on probabilistic approaches. Additionally, we have performed experiments during the scheduled secondment at Université de Lausanne, Switzerland to validate our theoretical findings. The impact of the project DIPHORES on the society: Flows containing dissolved salts and suspended colloids occur in a variety of natural and engineered scenarios including groundwater contamination and remediation, enhanced oil recovery, textile industries, nuclear waste removal, water-filtration and management, microfluidics for biomedical applications, target drug delivery and so on. In all these situations, the presence of local salt gradients can induce particle migration via diffusiophoresis. From a fundamental point of view, this adds to the complexity of the problem at hand and provides ample opportunities for investigation. From a practical perspective, this phenomenon can be exploited for achieving particle manipulation and control, and subsequently improving the technological processes. This has a direct impact on the problems of high socio-economic and environmental relevance. The overall objectives of project DIPHORES: The objective of the project DIPHORES is to investigate how the microscopic interactions impact macroscopic particle transport in porous media by performing pore-scale simulations and experiments and to upscale the dynamics to macro or Darcy-scale for better prediction of the fate of the particles. By gaining a deeper understanding of this complex interplay between diffusiophoresis and the host medium flow disorder, we can design efficient technological applications especially in the context of groundwater remediation processes. To do so, we aim to understand the role of the various design parameters on the particle transport. Main conclusions of project DIPHORES: On the one hand, in a hybrid micro-nanofluidic setup, we show that diffusiophoresis can be exploited for achieving selective particle separation and analysis. This separation process can be further optimized as a function of the relevant design parameters. These results are particularly crucial in the field of microfluidics for biomedical applications where selective particle separation is desired. On the other hand, in a hyper-uniform porous structure characterized by dead-end pores and transmitting pores, we show that the presence of local salt concentration gradients gives rise to an additional colloid motion via diffusiophoresis that couples with the advection and diffusion ones. Depending on the mobility, it is possible to enhance transport out of the dead-end pores with stagnant flow or to promote particle trapping within. These results are at the frontier of the field and will pave the way for controlled particle manipulation and control through porous media, impacting processes such as groundwater remediation and water-filtration.

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