We present our recent work, developing and applying simulation methods to gain atomistic insights into the factors controlling the adsorption of ions and molecules at mineral-water interfaces. Our approach involves the use of plane-wave DFT including van der Waals interactions coupled with experimental data to validate force field models which are then applied within energy minimization (EM) and classical molecular dynamics (MD) techniques. This combination means that we can explore the evolution of systems of different sizes and for different lengths of time allowing for an efficient evaluation of structures and dynamical properties, not least free energies of adsorption.  The main focus of this investigation is evaluating the relative efficiency of different layered minerals including metal hydroxides and clay minerals as geosorbents in the aqueous environment.  The metal hydroxides include portlandite, which is used in many applications including acid neutralisation, agriculture and waste water treatment and clay materials including montmorillonite, again used in water treatment as well as heavy and radioactive metal remediation.   We find that the adsorption of a range of different molecules found in the environment depends not only on the structure of the interface but also on the charge state of the species concerned.   One of the important features of atomistic simulation is that it is able to identify the effect of different factors. For example, adsorption on these materials is normally thought to occur primarily on the basal plane, which dominates their morphologies, and hence has been the focus of many investigations. However, the edge surfaces are more reactive and can potentially have a greater range of compositions and charge states and we show how the edge surfaces can indeed provide more efficient sites for adsorption.

Atomistic simulation of adsorption at the mineral-water interface

247th National Meeting (2014)

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