Manufactured nanoparticles: assessing the mobility of a future class of containment in groundwaters

Estimating manufactured nanoparticle mobility using fast, simple methods could form a useful part of a risk assessment tool. The aim of this work was to investigate whether zeta potential could be used for this purpose. \n \nUsing a new surface zeta potential measurement technique, the surface zeta potential of a 50m sandstone sequence was found to vary little with lithofacies when chemical conditions were kept constant. A surface area modified linear mixing model was able to describe the sandstone zeta potential, suggesting that clay minerals are the dominant control on bulk properties. \n \nThe sandstone and silica nanoparticle zeta potentials were sensitive to the chemical composition and pH of the surrounding fluid, which was influenced by ion exchange and carbonate dissolution. The zeta potential of the sandstone and nanoparticles can be used to qualitatively describe the relative mobility under different chemical conditions. \n \nCalculations using DLVO and colloid filtration theory (CFT) can reproduce the equilibrium concentration (C’/C\\(_0\\)) values observed experimentally, however the significant tailing in the breakthrough curve is not described by this traditional particle transport model. Further work is required to determine whether DLVO and CFT can be used as part of a mobility screening tool, as this initial study suggests.