X-RAY PHOTOELECTRON-SPECTRA OF THE PALLADIUM-IRON BIMETALLIC SURFACE USED FOR THE RAPID DECHLORINATION OF CHLORINATED ORGANIC ENVIRONMENTALCONTAMINANTS

Palladized iron (Pd/Fe) has been successfully used for the rapid dechl orination of organic environmental contaminants in aqueous solutions. We have investigated the nature of the Pd/Fe surface by X-ray photoele ctron spectroscopy. Our results indicate that the reactive Pd/Fe surfa ce is formed by the stepwise reduction of Pd(IV) in solution to Pd(II) , which replaces protons on the hydroxylated iron oxide surface and fo rms Pd(II)-0-Fe bonds. These-bonds are unstable and collapse spontaneo usly to yield the reactive palladized iron in which the palladium is i n the elemental state. Prolonged exposure of this Pd/Fe surface to a s aturated solution of aqueous TCE results in the growth of the hydroxyl ated iron oxide film that deactivates the Pd/Fe surface. The thick hyd roxylated iron oxide film can be removed, and the original activity of the Pd/Fe surface can be restored by washing the surface with a dilut e acid solution.