An in situ IR spectroscopic investigation of adsorption of hexa- and penta-cyanoferrates to metla oxides from aqueous solution

摘要

The adsorption of some hexa- and penta-cyanoferrate ions to ~everal metal oxides from aqueous solutions ha been investigated by in situ IR spectroscopy. Thin TiO2 , ZrO2 , AI2O3 and Ta2OsParticle films were prepare on ZnSe and Ge 45° attenuated total internal reflection prisms and CaF 2 transmi~sion IR windows by drying of aqueous sols. The Fe(n) adsorbates, [Fe(CN)6]4- and [Fe(CN)sNH3]3-, were both found to coordinate to the metal oxides. [Fe(CN)6]4- binds via anatnbidentate --CN-ligand,while [Fe(CN)sNH3]3- binds ina bidentate fashion with displacement of the -NH3 ligand from the Fe(n)coordination sphere. Adsorption of th Fe(lII) adsorbates: [Fe(CN)6]3-, [Fe(CN)sNH3J2- and [Fe(CN)sH20J2-, to metal oxides prepared on ZnSe was found to involve: (i) electrostatically adsorbed species, (ii) the formation of Zn2+-adsorbatecomplexes on the prism surface and (iii) reduction of the Fe(lII)adsorbates at photo-generated surface reduction centres forming adsorbed Fe(n) products. Adsorption of the Fe(III) adsorbates to metal oxides prepared on Ge prisms was also found to involve only surface complexation of an Fe(n) product following reduction viaGe, while adsorption to films prepared on CaF 2 showed only electrostatically adsorbed species.