Impact of interfacial adsorption of nanoparticles on transport properties

We study the transport and adsorption of nanoparticles in partially saturated porous media experimentally. Using fluorescent microscopy in two-dimensional model porous media we measure the distribution and breakthrough of nanoparticles at small flow rates. Our results show that at large Peclet numbers, nanoparticles primarily follow the major flow paths while they tend to diffuse close to the interfaces and solid structure at small Peclet numbers. Comparing the breakthrough of nanoparticles in a fully saturated porous medium with a medium partially saturated with a second immiscible fluid shows that by increasing the number of interfaces a smaller number of nanoparticles are discharged from the medium. The impact of interfacial adsorption of nanoparticles strongly depends on the nanoparticle charges and wettability of the medium.