On the anomalous adsorption of [Pd(edta)]2- at the water/Goethite interface: spectroscopic evidence for two types of surface complexes.
The structure of palladium(II) ethylenediaminetetraacetate (edta) in aqueous solutions and its adsorption on the surface of goethite (alpha-FeOOH) were studied using extended X-ray absorption fine structure spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. The obtained results show that in aqueous solutions, Pd-edta exists as a 1:1 complex, [Pd(edta)]2-, with edta acting as a quadridentate ligand. On the surface of goethite, [Pd(edta)]2- forms two different types of complexes over a pH range of 3.40-8.12. At pH < 5, [Pd(edta)]2- adsorbs as an outer-sphere species with possible hydrogen bonding. At higher pH values, the formation of inner-sphere complexes of the cation-type sets in after a cleavage of one glycinate ring and the formation of an (edta)Pd-O-Fe linkage.
Kaplun
Marina
M
Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden. ztmkaplun@gmail.com
Nordin
Agneta
A
Persson
Per
P
D000327:Adsorption; D004492:Edetic Acid / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D010165:Palladium / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water
D014867:Water; D010165:Palladium; D004492:Edetic Acid