ATTENUATED TOTAL-REFLECTION FOURIER-TRANSFORM INFRARED SPECTROSCOPIC INVESTIGATION OF THE SOLID AQUEOUS INTERFACE OF LOW SURFACE-AREA, WATER-SOLUBLE SOLIDS IN HIGH IONIC-STRENGTH, HIGHLY ALKALINE, AQUEOUS-MEDIA/

A new method for the investigation of the adsorption of the series of surface active quaternary ammonium (QA) compounds, dodecyltrimethylamm onium bromide (C12), tetradecyltrimethylammonium bromide (C14), and he xadecyltrimethylammonium bromide (C16) on the surface of sodium oxalat e-a Bayer process solid-has been developed using Fourier transform inf rared (FTIR) attenuated total reflection (ATR) spectroscopy. The techn ique involves the use of a finely ground sodium oxalate combined with an appropriate adsorption matrix and, for the first time, permits the in situ investigation of adsorption from high ionic strength, highly a lkaline (pH 12), aqueous media onto a water soluble, low surface area solid: sodium oxalate (a compound traditionally treated as ligand or a dsorbate). Spectroscopic results show the formation of surfactant aggr egate clusters on the surface of sodium oxalate and suggest adsorption in the order C16 > C14 > C12. This new method will allow the acquisit ion of ''dose-response'' curves for the C12, C14, and C16 QAs on sodiu m oxalate (under the aforementioned conditions), while also leading to the in situ investigation of the surface of sodium oxalate in synthet ic and process Bayer liquors (high ionic strength, extremely alkaline media). Our results suggest that this method will be well suited to in terfacial research in other similar areas involving complex, nonideal industrial systems which also depend upon chemical processes occurring at the solid/aqueous and solid/liquid interfaces.