FT-IR, XPS, and DFT Study of Adsorption Mechanism of Sodium Acetohydroxamate onto Goethite or Hematite

Abstract

The adsorption of sodium acetohydroxamate on the goethite or hematite surface was investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray photoemission spectroscopy and periodic plane-wave density functional theory (DFT) calculations. The core-level shifts and charge transfers of the adsorbed surface iron sites calculated by DFT with periodic interfacial structures were confronted to the X-ray photoemission experiments. FT-IR results reveal that the interfacial structure of sodium acetohydroxamate adsorbed on the goethite or hematite surface may be assigned to a five-membered ring complex. In agreement with the adsorption energies determined by the DFT calculations, a five-membered ring complex is formed via bonding of one surface iron atom of goethite (101) or (100) to both oxygen atoms of hydroxamate group, and these two oxygen atoms of the hydroxamate group correspondingly attach to two neighboring iron atoms of the goethite surface. But a five-membered ring complex between two oxygen atoms of the hydroxamate group and one surface iron atom of hematite (001) is formed without any extra attachments. The calculated core-level shifts of Fe2p for the interfacial structures are correspondingly in good agreement with the experimental observed one, which confirmed the reliability of the calculated results.