Spectroscopic study of the simultaneous adsorption of PVP and azelaic acidon gamma-alumina

The adsorption mechanism of 1-vinyl-2-pyrrolidone (VP), poly(1-vinyl-2-pyrr olidone) (PVP), and azelaic acid was investigated on synthetic gamma -alumi num oxide surfaces using FT-IR, FT-Raman, UV, and C-13 NMR spectroscopy (so lid state). It was found that VP adsorption from ethylene glycol (EG) solut ion, as well as PVP adsorption from both aqueous and EG solutions, was negl igible. m the case of EC solutions, the solvent adsorbed at the gamma -alum ina surface. The presence of dicarboxylic acid enhances the adsorption of t he PVP, due to a hydrophobic interaction between the carbon chains of the p olymer and the dicarboxylic acid. The simultaneous adsorption of PVP and az elaic acid was studied as a function of time, pH, and solvent in order to e stablish a more detailed surface complexation model. Surface complexation o f azelaic acid in aqueous solution starts with mainly outer sphere coordina tion, driven by electrostatic forces, which is transformed to an inner sphe re complex in time, forming a covalent bond between the carboxylate entity and the alumina surface, especially at low pH. At high pH the outer sphere complex is dominating.