Vote here for: Drew Aleto (#Fishbone) Abstract: Hydroxyapatite [HAP, Ca10(PO4)6(OH)2] is well documented as a metals sequestration medium. Here, its surface was amended to enhance these properties and tested on two aqueous contaminants: As, a metalloid in its arsenite and arsenate oxoanionic forms, and U(VI), a cationic metal. For As, the surface was amended with either Fe(II) or Fe(III), forming amorphous phases of iron phosphates. For U(VI), the HAP surface was amended by creating a vanadate-substituted near-surface rind. Unamended HAP was tested as a control medium. A series of flow-through and batch laboratory-based experiments were conducted to test removal efficacy. The material surface areas were analyzed using the BET method. Resulting solutions were analyzed via ICP-MS. Solid-phase analyses were performed using TGA, SEM-EDS, TEM, and XRD to determine the resulting surface chemistry and crystallinity. Arsenite removal increased with increasing As(III) concentration with iron-modified HAP. Arsenate removal also increased with iron-modified HAP but decreased with increasing As(V) concentration. Removal trended similarly with ferrous-amended HAP. Thermodynamic modeling showed increased removal of U(VI) is favorable with the vanadate-amended HAP. The resulting mixed-phase uranyl vanadate-phosphates are more insoluble than pure-phase uranyl phosphates.
Posted on: Thu, 13 Nov 2014 18:08:10 +0000
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