Abstract
The drying of porous media is a ubiquitous phenomenon in soils and building materials. The fluid often contains suspended particles. Particle deposition may modify significantly the final material, as it could be pollutants or clogging the pores, decreasing the porosity, such as in salt, in which particles and drying kinetics are coupled. Here, we used SEM and X-ray microtomography to investigate the dried porous media initially saturated by nanoparticle suspensions. As the suspensions were dried, nanoparticles formed a solid deposit, which added to the initial solid matrix and decreased the porosity. We demonstrate that since the drying occurred through the top surface, the deposit is not uniform as a function of depth. Indeed, the particles were advected by the liquid flow toward the evaporative surface; the deposit was significant over a depth that depended on the initial volume fraction, but the pore size was affected over a very narrow length. These findings were interpreted in the frame of a physical model. This study may help to design better porous media and take into account particle influence in drying processes.
Highlights
The drying of porous media is a ubiquitous phenomenon
We demonstrate that since the drying occurred through the top surface, the deposit is not uniform as a function of depth
The porous porous media media initially initially saturated saturated by by aa suspension suspension of of nanoparticles nanoparticles were were monimonitored by mass loss during the evaporation process
Summary
The drying of porous media is a ubiquitous phenomenon. The liquid is rarely pure in most environments, but some particles are suspended, and salts are dissolved. The migration of colloids in soil and their deposition are significant for pollutant transport and soil structuration [1,2,3,4]. For building materials and cultural heritage stones, salt may deteriorate the matrix or lead to carbonation of the structures [5,6,7]. Many studies described the evaporation of pure water from porous media with micrometric pores. The general process of drying/drainage is driven by capillary forces [8,9,10,11]
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