InterPore2025

Surface washing of contaminated porous substrates

22 May 2025, 10:05

15m

Oral Presentation (MS16) Fluid Interactions with Thin Porous Media MS16

Speaker

Dr Merlin A. Etzold (Defence Science and Technology Laboratory)

Description

The cleaning and decontamination of various porous surfaces (e.g., concrete, tarmac, wood, etc.) is a challenging and multidisciplinary problem for both fundamental understanding and a wide range of industrial, medical, urban, everyday-life and disaster-response applications. The role of such processes is particularly crucial in cases where contaminants, such as chemical substances and biological pathogens, are extremely harmful and pose serious risks to human health. Indeed, attempts to decontaminate porous materials might lead to a partial redistribution of the unwanted substance within the porous matrix instead of a complete removal. As a result, cleaning operations could further contribute to the contaminant/virus spread, and the substance might remain a long-time hazard for people coming in contact with the contaminated medium.
We performed surface-washing experiments modelling the decontamination of porous media. The contaminant agent was simulated by a passive tracer (disodium-fluorescein solution) which was released onto the free porous surface in the form of droplets and was let to diffuse in the porous structure. The surface-washing was simulated by a thin gravity-driven water film flowing over the inclined porous-glass plane. A parametric analysis was conducted by varying parameters such as the amount of the contaminant, the angle of the porous plate with the horizontal, the time from the contaminant deposition on the porous plate until the start of washing, and the permeability of the porous plate. A novel method based on spectroscopy principles was developed to measure precisely the concentration of the contaminant that has been removed from the porous plate and is present in the effluent with time. Additionally, employing imaging techniques we extracted valuable qualitative information about the contaminant redistribution and removal. Our experiments provided insights on the fundamental physics governing the cleaning process, such as the role of the initial conditions and the impact of process parameters on the decontamination efficiency (e.g., needed amount of cleansing resources and washing time).