Monomer Adsorption on Kaolinite: Modeling the Essential Ingredients

In this study we investigate the fundamentals of a problem pertinent to the cement and concrete manufacturing industries, where clay minerals are pollutants of sands due to their capacity to adsorb additives designed to improve concrete workability. In this density functional theory (DFT) investigation we examine the adsorption of a selection of organic monomers, (e.g., CH3CH2CHOHCH3 and (CH3)(3)N+CH2CHOHCH2CH3,Cl-) on kaolinite (Al2Si2O5(OH)(4)) to determine the nature of the basal surface/monomer interactions and, also, to determine whether the presence of an additional clay layer and separately water changes the nature of these interactions We gauge these effects by examining their formation energies, structural configurations post relaxation, Mulliken charges, and molecular orbitals occupancies. The results show that interactions are predominantly electrostatic for charged monomers and H-bonding for noncharged and also that increasing the complexity of these systems does not change the nature of these interactions, but that it does change the strength of them as well as the potential chemical reactivity of these clay/monomer environments.