A spectroscopic study of phthalate adsorption on gamma-aluminum oxide

Surface complexation of phthalic acid/phthalate has been investigated on sy nthetically produced, nonaged gamma-aluminum oxide by infrared and Raman sp ectroscopy. Effects of time, pH, and ionic strength have been studied both on the total adsorbed amount of phthalate and on the surface complexes. The spectroscopic results indicated the formation of two different types of co mplexes: outer sphere and inner sphere. The relative concentrations of thes e complexes were shown to vary considerably with pH but very little with in creasing ionic strength, which equally reduced the amount of both types of complexes. Considering the electrostatic interaction between the surface an d adsorbate, a complexation model was proposed that is in accordance with t he spectroscopic results. Adsorption on the synthetic gamma-alumina was com pared to the adsorption on gamma-aluminum oxide films produced by anodic ox idation, where the adsorbed amount was greatly reduced; however, both inner - and outer-sphere types of complexation have been observed.