Adsorption of nitrogen-containing heterocyclic compounds from aqueous solutions on iron and alpha-FeO3

Adsorption of several pyridines on Armco iron and iron oxide was studied. I t was shown that selective adsorption of pyridine and some of its derivativ es on alpha-Fe2O3 from aqueous solutions could be caused both by the format ion of II-bonds between heterocyclic nitrogen and a hydroxylated surface of the oxide, and by specific interactions between organic molecules and the adsorbent, which arose as a result of the coincidence of electromagnetic en ergy absorption maxima in their electronic spectra. On the surface of Armco iron, specific adsorption was observed for compounds, whose characteristic frequencies were close to the absorption maxima of either iron or iron oxi de. Positive changes in the enthalpy of the surface layer were characterist ic of adsorption of heterocyclic compounds that specifically interacted wit h the surface of the metal.