At the solid/liquid interface: FTIR/ATR--the tool of choice

For the last 7 years, we have been researching various aspects of the Bayer process. Predominant among these has been the surface chemistry of Bayer process solids. To this end, we have been using Fourier transform infrared (FTIR) attenuated total reflection (ATR) spectroscopy for in situ studies of the surfaces of the Bayer process solids sodium oxalate and aluminium trihydroxide under extreme (high ionic strength, high pH), Bayer-like conditions. FTIR/ATR is one of the few techniques currently available to scientists wishing to explore solid/liquid interfacial phenomena in situ. Using this investigative technique, information regarding the nature of adsorbed species can be readily acquired, with details concerning adsorbate orientation and adsorption/desorption equilibria, speciation, mechanisms and kinetics obtainable. Not surprisingly, FTIR/ATR has become one of the tools of choice for those wishing to explore the solid/liquid interface, and the body of literature available on the subject has been steadily growing over the last 10-15 years. This review addresses the current state of knowledge in the area of FTIR/ATR with respect to interfacial spectroscopy, as well as introducing some of the more fundamental theoretical and practical aspects of the technique. Particular emphasis is placed upon applied interfacial research. In writing this review, we draw on a considerable amount of expertise in the use of FTIR/ATR in interfacial studies (in particular, the practical considerations involved), as well as a large and comprehensive literature database focussing primarily on the investigation of interfacial processes using the FTIR/ATR technique.