Molecular Dynamics Studieson the Adaptability ofan Ionic Liquid in the Extraction of Solid Nanoparticles.

Recently, a number of publications have suggested thationic liquids(ILs) can absorb solid particles. This development may have implicationsin fields likeoil sand processing, oil spill beach cleanup, and water treatment.In this Article, we provide a computational investigation of thisphenomenon via molecular dynamics simulations. Two particle surfacechemistries were investigated: (1) hydrocarbon-saturated and (2) silanol-saturated,representing hydrophobic and hydrophilic particles, respectively.Employing 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) as a model IL, these nanoparticles were allowed to equilibrateat the IL/water and IL/hexane interfaces to observe the interfacialself-assembled structures. At the IL/water interface, the hydrocarbon-basednanoparticles were nearly completely absorbed by the IL, while thesilica nanoparticles maintained equal volume in both phases. At theIL/hexane interface, the hydrocarbon nanoparticles maintained minimalinteractions with the IL, whereas the silica nanoparticles were nearlycompletely absorbed by it. Studies of these two types of nanoparticlesimmersed in the bulk IL indicate that the surface chemistry has agreat effect on the corresponding IL liquid structure. These effectsinclude layering of the ions, hydrogen bonding, and irreversible absorptionof some ions to the silica nanoparticle surface. We quantify theseeffects with respect to each nanoparticle. The results suggest thatILs likely exhibit this absorption capability because they can formsolvation layers with reduced dynamics around the nanoparticles. [ABSTRACT FROM AUTHOR]