title: Quantified Pore-Scale Nanoparticle Transport in Porous Media and the Implications for Colloid Filtration Theory.
abstract: This study evaluates the pore-scale distribution of silver nanoparticles during transport through a sandy porous medium via quantitative synchrotron X-ray computed microtomography (qSXCMT). The associated distributions of nanoparticle flow velocities and mass flow rates were obtained by coupling these images with computational fluid dynamic (CFD) simulations. This allowed, for the first time, the comparison of nanoparticle mass flow with that assumed by the standard colloid filtration theory (CFT) modeling approach. It was found that (i) 25% of the pore space was further from the grain than assumed by the CFT model; (ii) the average pore velocity agreed well between results of the coupled qSXCMT/CFD approach and the CFT model within the model fluid envelope, although the former were 2 times larger than the latter in the centers of the larger pores and individual velocities were upwards of 20 times those in the CFT model at identical distances from grain surfaces ; and (iii) approximately 30% of all nanoparticle mass and 38% of all nanoparticle mass flow occurred further away from the grain surface than expected by the CFT model. This work suggests that a significantly smaller fraction of nanoparticles than expected will contact a grain surface by diffusion via CFT models, likely contributing to inadequate CFT model nanoparticle transport predictions.
authors.affiliation: Department of Civil and Environmental Engineering, The University of Western Ontario , London, ON, Canada N6A 5B9.
authors.forename: Ian L
authors.initials: IL
authors.lastname: Molnar
authors.forename: Paula C
authors.initials: PC
authors.lastname: Sanematsu
authors.affiliation: Department of Civil and Environmental Engineering, The University of Western Ontario , London, ON, Canada N6A 5B9.
authors.forename: Jason I
authors.initials: JI
authors.lastname: Gerhard
authors.forename: Clinton S
authors.initials: CS
authors.lastname: Willson
authors.affiliation: Department of Civil and Environmental Engineering, The University of Western Ontario , London, ON, Canada N6A 5B9.|School of Civil and Environmental Engineering, Connected Water Initiative, University of New South Wales , Manly Vale, NSW 2093, Australia.
authors.forename: Denis M
authors.initials: DM
authors.lastname: O'Carroll