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Title: Phosphate-Induced Immobilization of Uranium in Hanford Sediments

Abstract

Phosphate can be added to subsurface environments to immobilize U(VI) contamination. The efficacy of immobilization depends on the site-specific groundwater chemistry and aquifer sediment properties. Batch and column experiments were performed with sediments from the Hanford 300 Area in Washington State and artificial groundwater prepared to emulate the conditions at the site. Batch experiments revealed enhanced U(VI) sorption with increasing phosphate addition. X-ray absorption spectroscopy measurements of samples from the batch experiments found that U(VI) was predominantly adsorbed at conditions relevant to the column experiments and most field sites (low U(VI) loadings, <25 μM), and U(VI) phosphate precipitation occurred only at high initial U(VI) (>25μM) and phosphate loadings. While batch experiments showed the transition of U(VI) uptake from adsorption to precipitation, the column study was more directly relevant to the subsurface environment because of the high solid:water ratio in the column and the advective flow of water. In column experiments, nearly six times more U(VI) was retained in sediments when phosphate-containing groundwater was introduced to U(VI)-loaded sediments than when the groundwater did not contain phosphate. This enhanced retention persisted for at least one month after cessation of phosphate addition to the influent fluid. Sequential extractions and laser-induced fluorescence spectroscopy ofmore » sediments from the columns suggested that the retained U(VI) was primarily in adsorbed forms. These results indicate that in situ remediation of groundwater by phosphate addition provides lasting benefit beyond the treatment period via enhanced U(VI) adsorption to sediments.« less

Authors:
; ORCiD logo; ; ; ORCiD logo;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1358519
Report Number(s):
PNNL-SA-126170
Journal ID: ISSN 0013-936X; 47951; KP1702030
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 50; Journal Issue: 24
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Environmental Molecular Sciences Laboratory

Citation Formats

Pan, Zezhen, Giammar, Daniel E., Mehta, Vrajesh, Troyer, Lyndsay D., Catalano, Jeffrey G., and Wang, Zheming. Phosphate-Induced Immobilization of Uranium in Hanford Sediments. United States: N. p., 2016. Web. doi:10.1021/acs.est.6b02928.
Pan, Zezhen, Giammar, Daniel E., Mehta, Vrajesh, Troyer, Lyndsay D., Catalano, Jeffrey G., & Wang, Zheming. Phosphate-Induced Immobilization of Uranium in Hanford Sediments. United States. doi:10.1021/acs.est.6b02928.
Pan, Zezhen, Giammar, Daniel E., Mehta, Vrajesh, Troyer, Lyndsay D., Catalano, Jeffrey G., and Wang, Zheming. Tue . "Phosphate-Induced Immobilization of Uranium in Hanford Sediments". United States. doi:10.1021/acs.est.6b02928.
@article{osti_1358519,
title = {Phosphate-Induced Immobilization of Uranium in Hanford Sediments},
author = {Pan, Zezhen and Giammar, Daniel E. and Mehta, Vrajesh and Troyer, Lyndsay D. and Catalano, Jeffrey G. and Wang, Zheming},
abstractNote = {Phosphate can be added to subsurface environments to immobilize U(VI) contamination. The efficacy of immobilization depends on the site-specific groundwater chemistry and aquifer sediment properties. Batch and column experiments were performed with sediments from the Hanford 300 Area in Washington State and artificial groundwater prepared to emulate the conditions at the site. Batch experiments revealed enhanced U(VI) sorption with increasing phosphate addition. X-ray absorption spectroscopy measurements of samples from the batch experiments found that U(VI) was predominantly adsorbed at conditions relevant to the column experiments and most field sites (low U(VI) loadings, <25 μM), and U(VI) phosphate precipitation occurred only at high initial U(VI) (>25μM) and phosphate loadings. While batch experiments showed the transition of U(VI) uptake from adsorption to precipitation, the column study was more directly relevant to the subsurface environment because of the high solid:water ratio in the column and the advective flow of water. In column experiments, nearly six times more U(VI) was retained in sediments when phosphate-containing groundwater was introduced to U(VI)-loaded sediments than when the groundwater did not contain phosphate. This enhanced retention persisted for at least one month after cessation of phosphate addition to the influent fluid. Sequential extractions and laser-induced fluorescence spectroscopy of sediments from the columns suggested that the retained U(VI) was primarily in adsorbed forms. These results indicate that in situ remediation of groundwater by phosphate addition provides lasting benefit beyond the treatment period via enhanced U(VI) adsorption to sediments.},
doi = {10.1021/acs.est.6b02928},
journal = {Environmental Science and Technology},
number = 24,
volume = 50,
place = {United States},
year = {Tue Dec 20 00:00:00 EST 2016},
month = {Tue Dec 20 00:00:00 EST 2016}
}