INSITU CIR-FTIR CHARACTERIZATION OF SALICYLATE COMPLEXES AT THE GOETHITE AQUEOUS-SOLUTION INTERFACE

The types of complexes that salicylate (2-hydroxybenzoate) forms with the surface of goethite (α-FeOOH) in aqueous medium were studied in situ by using cylindrical internal reflection (CIR) Fourier transform infrared (FTIR) spectroscopy. Results obtained from CIR-FTIR studies were compared with adsorption isotherm experiments in order to relate the level of salicylate coverage to the nature of the surface complex. At lower surface coverages all the interfacial salicylate has a chelate structure in which one carboxylic oxygen and the ortho phenolic oxygen bind one Fe atom of the goethite surface. At higher surface coverages this chelate complex coexists with salicylate ions, which are weakly bound in the double layer. © 1990, American Chemical Society. All rights reserved.