| Attributs | Valeurs |
|---|
| type
| |
| Is Part Of
| |
| Subject
| |
| Title
| - Hydrogarnet: A Host Phase forCr(VI) in Chromite Ore ProcessingResidue (COPR) and Other High pHWastes
|
| has manifestation of work
| |
| related by
| |
| Author
| |
| Abstract
| - For understanding both the environmental behavior anddeveloping remediation treatments for chromium oreprocessing residue (COPR) it is important to identify allthe potentially soluble sources of Cr(VI). Hydrogarnet hasbeen identified as a major phase in COPR and it hasbeen previously speculated that it has a capacity to hostCr(VI). Here we provide direct evidence of this capacity bydemonstrating the incorporation of Cr(VI) into laboratorysynthesized hydrogarnet. Electron microscopy and energydispersive X-ray microanalysis show incorporation ofapproximately 17 000−22 000 mg Cr(VI) kg-1 hydrogarnet.X-ray powder diffraction data show that peak intensities arealtered by chromium substitution and that chromiumsubstituted hydrogarnets have a smaller unit cell than thepure Ca−Al end member. This is consistent withsubstitution of hydroxyl tetrahedra by smaller chromatetetrahedra. Electron energy loss spectroscopy confirms thetetrahedral coordination and hexavalent oxidation stateof chromium in the hydrogarnets. The maximum amount ofhexavalent chromium that can be introduced syntheticallycorresponds to a replacement of about one out ofevery eight hydroxyl tetrahedral per unit cell by a CrO42-tetrahedra and tallies closely with the amount of chromiummeasured in hydrogarnets from COPR. Chromium-bearinghydrogarnet is the most abundant crystalline phase in millionsof tons of COPR contaminating land around Glasgow,Scotland, and was recently identified in COPR from sitesin North America. Calculations based on its abundance andits Cr(VI) content indicate that hydrogarnet can host asmuch as 50% of the Cr(VI) found in some COPR samples.
|
| article type
| |
| is part of this journal
| |
