Interaction of gibbsite with oleic acid: Surface energetics and modelling

Abstract

We examined the surface interaction energetics of gibbsite with oleic acid by employing both experimental techniques and quantum chemical calculations. The infrared frequencies computed for the pure oleic acid as well as for the sodium–oleate complex using the Amsterdam Density Functional program show a shift to lower wavenumbers associated with the formation of a metal-carboxylate fragment. Our MSINDO calculations indicate that the oleic acid-surface complex may form and influence the growth of gibbsite at a pH range of 5 to 9 as compared to more alkaline pH, however adsorption is most favoured at defect and dopant sites. Comparison of the theoretical results with experimental findings imply the possible role of intermediate species such as sodium–oleate at high pH. The morphological importance of the [110] prismatic face is shown by the more favourable adsorption energies for oleic acid (−201kJ/mol) and sodium–oleate (−173kJ/mol) evaluated for this face.