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Method to Attenuate U(VI) Mobility in Acidic Waste Plumes Using Humic Acids.

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Title: Method to Attenuate U(VI) Mobility in Acidic Waste Plumes Using Humic Acids.
Authors: Jiamin Wan1 jwan@lbl.gov, Wenming Dong1, Tokunaga, Tetsu K.1
Source: Environmental Science & Technology. 3/15/2011, Vol. 45 Issue 6, p2331-2337. 7p.
Subject Terms: *In situ remediation, *Groundwater remediation, *Humic acid, *Uranium mining & the environment, *Groundwater pollution, *Uranium & the environment, *Plutonium & the environment, *Biodegradation, Migration of uranium
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 5896 immobilized ih 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 intraducible to the subsurface. [ABSTRACT FROM AUTHOR]
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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 5896 immobilized ih 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 intraducible to the subsurface. [ABSTRACT FROM AUTHOR]
ISSN:0013936X
DOI:10.1021/es103864t