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Coadsorption of Cu(II) and glyphosate at the water-goethite (alpha-FeOOH) interface: molecular structures from FTIR and EXAFS measurements

Author:
  • J. Sheals
  • M. Granstrom
  • S. Sjoberg
  • Per Persson
Publishing year: 2003
Language: English
Pages: 38-47
Publication/Series: Journal of Colloid and Interface Science
Volume: 262
Document type: Journal article
Publisher: Elsevier
Additional info: 1

Abstract english

The coadsorption of Cu(II) and glyphosate (N-(phosphonomethyl)glycine, abbreviated to PMG) at the water-goethite interface was studied by means of batch adsorption experiments, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The system was investigated over the pH range 3-9 and at total concentrations of 0.9 mumol and 2.2 mumol Cu(II) and PMG per m(2) of goethite. The collective quantitative and spectroscopic results show that Cu(II) and PMG directly interact at the water-goethite interface to form ternary surface complexes. Two predominating complexes have been identified. At pH 4 the IR and CuK-edge EXAFS data indicate a molecular structure where the phosphonate group of PMG bonds monodentately to the surface in an inner sphere mode, while carboxylate and amine groups coordinate to Cu(II) to form a 5-membered chelate ring. Hence, at pH 4, Cu(II) and PMG form a ternary surface complex on goethite with the general structure goethite-PMG-Cu(II). At the highest pH investigated (pH 9), the carboxylate group is still coordinated to Cu(II) but the phosphonate group is present in a relatively free, noncoordinated and/or disordered state. Although the spectroscopic data are not conclusive they indicate the formation of ternary surface complexes with the molecular architecture goethite-Cu(II)-PMG at high pH. (C) 2003 Elsevier Science (USA). All rights reserved.

Keywords

  • Earth and Related Environmental Sciences

Other

Published
  • ISSN: 1095-7103
Per Persson
E-mail: per [dot] persson [at] biol [dot] lu [dot] se

Professor

MEMEG

+46 46 222 17 96

+46 70 266 38 79

E-C350

50

Professor

Centre for Environmental and Climate Research (CEC)

+46 46 222 17 96

+46 70 266 38 79

D350

Ekologihuset, Sölvegatan 37, Lund

50