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This article in JEQ

  1. Vol. 33 No. 4, p. 1280-1287
     
    Received: July 30, 2003
    Published: July, 2004


    * Corresponding author(s): wanghp@mail.ncku.edu.tw
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doi:10.2134/jeq2004.1280

In Situ Speciation Studies of Copper–Humic Substances in a Contaminated Soil during Electrokinetic Remediation

  1. S.-H. Liu and
  2. H. Paul Wang *
  1. Department of Environmental Engineering, National Cheng Kung University, Tainan City 70101, Taiwan

Abstract

Speciation of copper–humic substances (HS) in the electrokinetic remediation (EKR) of a contaminated soil was studied by in situ extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies. The least-square fits of the XANES spectra suggested that the main Cu species in the contaminated soil were Cu–HS (50%), CuCO3 (28%), Cu2O (11%), and CuO (11%). The Cu–HS in the contaminated soil possessed equatorial and axial Cu–O bond distances of 1.94 and 2.17 Å with coordination numbers (CNs) of 3.6 and 1.4, respectively. In the EKR process, the axial Cu–O bond distance in the Cu–HS complexes was increased by 0.15 Å, which might be due to a ligand exchange of the Cu–HS with H2O molecules in the electrolyte. After 180 min of EKR, about 50% of the Cu–HS complexes (or 24% of total Cu) in the soil were dissolved and formed [Cu(H2O)6]2+ in the electrolyte, 71% (or 17% of total Cu in the soil) of which were migrated to the cathode under the electric field (5 V/cm). This work exemplifies the use of in situ EXAFS and XANES spectroscopies for speciation studies of Cu chelated with HS in the contaminated soil during EKR.

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