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This article in SSSAJ

  1. Vol. 47 No. 1, p. 43-46

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Copper(II) Binding by Humic Acid Extracted from Sewage Sludge: An Electron Spin Resonance Study1

  1. Stephen A. Boyd,
  2. Lee E. Sommers,
  3. Darrell W. Nelson and
  4. Douglas X. West2



Electron spin resonance (ESR) spectroscopy was used to study the binding of Cu2+ by humic acid (HA) extracted from sewage sludge. Electron spin resonance spectral data of the Cu-HA complex and some adducts with nitrogen donors (pyridine, 1,10-phenanthroline, ethylenediamine) showed that Cu2+ formed two equatorial bonds with HA oxygen donor ligands. The ESR data presented were consistent with the formation of a Cu-chelate in the original Cu-HA complex. The ligand field strength of the HA oxygen donor ligands coordinated to Cu2+ was stronger than that of H2O. The above results were consistent with an earlier ESR characterization of a soil Cu-HA complex. The Cu2+ ion also appeared to form axial bonds with HA donor ligands originating from proteinaceous materials associated with the sludge HA fraction. Characterization of an adduct with glycylglycine showed that the dipeptide formed coordinate honds with Cu2+ bound to HA.

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