title: In situ speciation studies of copper-humic substances in a contaminated soil during electrokinetic remediation.
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%), CuCO(3) (28%), Cu(2)O (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 A 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 A, which might be due to a ligand exchange of the Cu-HS with H(2)O 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(H(2)O)(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.
authors.affiliation: Department of Environmental Engineering, National Cheng Kung University, Tainan City 70101, Taiwan.
authors.forename: S-H
authors.initials: SH
authors.lastname: Liu
authors.forename: H Paul
authors.initials: HP
authors.lastname: Wang
mesh_terms: D003300:Copper / Q000737:chemistry*; D004563:Electrochemistry; D004784:Environmental Monitoring / Q000379:methods; D004787:Environmental Pollution / Q000517:prevention & control; D006812:Humic Substances / Q000032:analysis*; D007700:Kinetics; D012989:Soil Pollutants / Q000032:analysis*; D013057:Spectrum Analysis
chemical_list: D006812:Humic Substances; D012989:Soil Pollutants; D003300:Copper