title: Interactions of Tc(IV) with humic substances.
abstract: To understand the key processes affecting 99Tc mobility in the subsurface and help with the remediation of contaminated sites, the binding constants of several humic substances (humic and fulvic acids) with Tc(IV) were determined, using a solvent extraction technique. The novelty of this paper lies in the determination of the binding constants of the complexes formed with the individual species TcO(OH)+ and TcO(OH)2(0). Binding constants were found to be 6.8 and between 3.9 and 4.3, for logβ1,-1,1 and logβ1,-2,1, respectively; these values were little modified by a change of ionic strength, in most cases, between 0.1 and 1.0 M, nor were they by the nature and origin of the humic substances. Modeling calculations based on these show TcO(OH)-HA to be the predominant complex in a system containing 20 ppm HA and in the 4-6 pH range, whereas TcO(OH)2(0) and TcO(OH)2-HA are the major species, in the pH 6-8 range.
authors.affiliation: Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, United States.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Boggs
authors.forename: Travis
authors.initials: T
authors.lastname: Minton
authors.forename: Wenming
authors.initials: W
authors.lastname: Dong
authors.forename: Samuel
authors.initials: S
authors.lastname: Lomasney
authors.forename: Mohammed R
authors.initials: MR
authors.lastname: Islam
authors.forename: Baohua
authors.initials: B
authors.lastname: Gu
authors.forename: Nathalie A
authors.initials: NA
authors.lastname: Wall
mesh_terms: D000327:Adsorption; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D012990:Soil Pollutants, Radioactive / Q000737:chemistry*; D013667:Technetium / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D012990:Soil Pollutants, Radioactive; D013667:Technetium