title: Method to attenuate U(VI) mobility in acidic waste plumes using humic acids.
abstract: Acidic uranium (U) groundwater plumes have resulted from acid-extraction of plutonium during the Cold War and from U mining and milling operations. A sustainable method for in situ immobilization of U under acidic conditions is not yet available. Here, we propose to use humic acids (HAs) for in situ U immobilization in acidic waste plumes. Our laboratory batch experiments show that HA can adsorb onto aquifer sediments rapidly, strongly and practically irreversibly. Adding HA greatly enhanced U adsorption capacity to sediments at pH below 5.0. Our column experiments using historically contaminated sediments from the Savannah River Site under slow flow rates (120 and 12 m/year) show that desorption of U and HA were nondetectable over 100 pore-volumes of leaching with simulated acidic groundwaters. Upon HA-treatment, 99% of the contaminant [U] was immobilized at pH ≤ 4.5, compared to 5% and 58% immobilized in the control columns at pH 3.5 and 4.5, respectively. These results indicate that HA-treatment is a promising in situ remediation method for acidic U waste plumes. As a remediation reagent, HAs are resistant to biodegradation, cost-effective, nontoxic, and easily introducible to the subsurface.
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States. jwan@lbl.gov
authors.forename: Jiamin
authors.initials: J
authors.lastname: Wan
authors.forename: Wenming
authors.initials: W
authors.lastname: Dong
authors.forename: Tetsu K
authors.initials: TK
authors.lastname: Tokunaga
mesh_terms: D000327:Adsorption; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008906:Mining; D014501:Uranium / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D014875:Water Pollutants, Radioactive; D014501:Uranium