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

Project Information

DIPHORES

Grant agreement ID: 895569

DOI

10.3030/895569

Project closed

EC signature date 21 April 2020

Start date 1 August 2020

End date 31 July 2022

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 172 932,48

EU contribution

€ 172 932,48

Coordinated by

UNIVERSIDAD POLITECNICA DE MADRID
Spain

Periodic Reporting for period 1 - DIPHORES (Pore-scale simulations to study the interaction of DIffusioPHORESis, flow and transport through porous media)

Reporting period: 2020-08-01 to 2022-07-31

Summary of the context and overall objectives of the project

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.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We performed two- and three-dimensional pore-scale simulations in (a) hybrid micro-nanochannel and (b) micromodel porous media setups. For the former, we show that it is possible to achieve selective particle separation via diffusiophoresis by imposed steady-state salt concentration gradients. We quantify the separation efficiency as a function of the relevant design parameters and compare with existing experiments in the literature. We also investigate the role of diffusioosmosis that refers to the bulk flow adjacent to the solid surfaces. These results were presented at InterPore2021 online (due to COVID-19), May 31 - June 4, 2021, and published in the journal of Physical Review Applied.

For the latter, we considered a hyperuniform pore structure that is statistically homogeneous and characterized by dead-end pores and transmitting pores. The porous medium is initially saturated with salt at a lower concentration and particles, and then eluted by injecting a sharp front of salt at higher concentration. This also serves as the driving force for diffusiophoresis within the stagnation points created inside the dead-end pores. We show that, depending on the diffusiophoretic mobility, which is a quantitative measure of the strength of the phoretic motion, diffusiophoresis can lead to particle mobilization out of the dead-end pores enhancing the macroscopic particle transport or conversely, it may promote particle trapping or deposition within the dead-end pores effectively deteriorating the macroscopic particle transport. In summary, our results suggest that diffusiophoresis is a powerful tool that can be exploited for achieving controlled particle manipulation and either improve the elution or deposition process, as desired. These results were presented at European Geosciences Union General Assembly, April 3-8, 2022 (EGU22) in Vienna, Austria, and Gordon Research Conference (GRC) on Flow transport and permeable media, July 17-22, 2022, in Les Diablerets, Switzerland where I received the ‘best poster’ award. Additionally, I was invited to present my work at Gordon Research Seminar (GRS) on Flow transport and permeable media, July 16-17, 2022, in Les Diablerets, Switzerland. Several publications are still underway to solidify this work.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

This project has generated results that are expected to be pioneers in the field of diffusiophoresis in porous media. Using pore-scale simulations and experiments, we have gained a fundamental understanding of the microscopic interplay between the host medium disorder and the diffusiophoretic particle motion. While both, flow and transport in porous media and colloidal migration due to diffusiophoresis have been previously investigated and are active areas of research, the novelty of our work lies in the intersection of the two. Our results provide a proof of concept to exploit diffusiophoresis for a variety of natural and engineered scenarios of great socio-economic and environmental relevance including groundwater remediation, enhanced oil recovery, water-filtration systems, microfluidics for biomedical applications, target drug delivery, etc. We show that by tuning the relevant design parameters, diffusiophoresis can be a powerful tool for achieving particle manipulation that is desired in all these high-impact technological applications.

Diffusiophoretic particle motion driven by local salt concentration gradients

Selective particle separation and analysis via diffusiophoresis