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Immobilization of Cesium‐137 and Uranium in Contaminated Sediments Using Soil Amendments
Author(s) -
Seaman John C.,
Meehan T.,
Bertsch P.M.
Publication year - 2001
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2001.3041206x
Subject(s) - illite , leaching (pedology) , uranium , chemistry , amendment , zeolite , toxicity characteristic leaching procedure , soil contamination , contamination , soil water , caesium , environmental chemistry , sediment , nuclear chemistry , clay minerals , mineralogy , geology , metallurgy , heavy metals , materials science , inorganic chemistry , soil science , ecology , biochemistry , paleontology , biology , political science , law , catalysis
Batch and dynamic leaching methods were used to evaluate the effectiveness of hydroxyapatite (HA), illite, and zeolite, alone and in combination, as soil additives for reducing the migration of cesium‐137 ( 137 Cs + ) and uranium (U) from contaminated sediments. Amendment treatments ranging from 0 to 50 g kg −1 were added to the sediment and equilibrated in 0.001 M CaCl 2 After equilibration, the treatment supernatants were analyzed for 137 Cs + , U, PO 4 , and other metals. The residual sediments were then extracted overnight using one of the following: 1.0 M NH 4 Cl, 0.5 M CaCl 2 , or the Toxicity Characteristic Leaching Procedure (TCLP) extractant. Cesium was strongly sorbed to the contaminated sediments, presumably due to interlayer fixation within native illitic clays. In fact, 137 Cs + was below detection limits in the initial equilibration solutions, the CaCl 2 extract, and the TCLP solution, regardless of amendment. Extractants selective for interlayer cations (1.0 M NH 4 Cl) were necessary to extract measurable levels of 137 Cs + Addition of illitic clays further reduced Cs + extractability, even when subjected to the aggressive extractants. Zeolite, however, was ineffective in reducing Cs + mobility when subjected to the aggressive extractants. Hydroxyapatite was less effective than illite at reducing NH + 4 –extractable Cs + Hydroxyapatite, and mixtures of HA with illite or zeolite, were highly effective in reducing U extractability in both batch and leaching tests. Uranium immobilization by HA was rapid with similar final U concentrations observed for equilibration times ranging from 1 h to 30 d. The current results demonstrate the effectiveness of soil amendments in reducing the mobility of U and Cs + , which makes in‐place immobilization an effective remediation alternative.