Immobilization of Uranium in Contaminated Sediments by Hydroxyapatite Addition
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- 作者：J. Samuel Arey ; John C. Seaman ; and Paul M. Bertsch
- 刊名：Environmental Science & Technology
- 出版年：1999
- 出版时间：January 15, 1999
- 年：1999
- 卷：33
- 期：2
- 页码：337 - 342
- 全文大小：196K
- 年卷期：v.33,no.2(January 15, 1999)
- ISSN：1520-5851
文摘
Batch equilibrations were performed to investigate theability of hydroxyapatite (Ca5(PO4)3OH) to chemically immobilizeU in two contaminated sediment samples having differentorganic carbon contents (123 and 49 g kg-1, respectively).Apatite additions lowered aqueous U to near proposed drinkingwater standards in batch equilibrations of two distinctsediment strata having total U concentrations of 1703 and2100 mg kg-1, respectively. Apatite addition of 50 g kg-1reduced the solubility of U to values less than would beexpected if autunite (Ca(UO2)2(PO4)2·10H2O) was thecontrolling solid phase. A comparison of the two sedimenttypes suggests that aqueous phase U may be controlledby both the DOC content through complexation andthe equilibrium pH for a given apatite application rate.Sequential chemical extractions demonstrated that apatiteamendment transfers U from more chemically labilefractions, including water-soluble, exchangeable, and acid-soluble (pH 
2.55) fractions, to the Mn-occluded fraction(pH 1.26). This suggests that apatite amendmentredirects solid-phase speciation with secondary U phosphatesbeing solubilized due to the lower pH of the Mn-occluded extractant, despite the lack of significantquantities of Mn oxides within these sediments. Energydispersive X-ray (EDX) analysis conducted in a transmissionelectron microscope (TEM) confirmed that apatiteamendment sequesters some U in secondary Al/Fephosphate phases.
2.55) fractions, to the Mn-occluded fraction(pH 1.26). This suggests that apatite amendmentredirects solid-phase speciation with secondary U phosphatesbeing solubilized due to the lower pH of the Mn-occluded extractant, despite the lack of significantquantities of Mn oxides within these sediments. Energydispersive X-ray (EDX) analysis conducted in a transmissionelectron microscope (TEM) confirmed that apatiteamendment sequesters some U in secondary Al/Fephosphate phases.