[article]
| Titre : |
Determination of CrVI) in tannery waste by the chelation-extraction method |
| Type de document : |
texte imprimé |
| Auteurs : |
Edward E. Menden, Auteur ; Frank H. Rutland, Auteur ; Waldo E. Kallenberger, Auteur |
| Année de publication : |
1990 |
| Article en page(s) : |
p. 363-375 |
| Note générale : |
Bibliogr. |
| Langues : |
Américain (ame) |
| Index. décimale : |
675 Technologie du cuir et de la fourrure |
| Résumé : |
Significant levels of hexavalent chromium have been reported in two tannery-related wastes by commercial analytical laboratories using the chelation/extraction method (EPA method 7197). Further investigation at the LIA Laboratory of such waste materials for identical sources revealed that unique trivalent chromium organocompounds were present in both. These can be erroneously identified as hexavalent chromium by virtue of the specific analytical conditions employed by the chelation/extraction procedure. Indeed, no chromium (VI) was found in either waste sample. The error in the chelation/extraction determination of chromum (VI) resulted from chromium (III) organocompounds which were directly soluble in the extraction solvent, methylisobutyl ketone. These extractable chromium (III) compounds were not specifically identified, but were found to behave identically with chromium (III) soaps and similar organochromium compounds.
The distinction between chromium (VI) and extractable chromium (III) compounds was demonstrated by two changes to the chelation/extraction method. These changes help differentiate chromium states and effectively illustrate that failure to do so can lead to erroneous results with this particular analytical method. The first change was to eliminate the chelating agent that complexes hexavalent chromium and, therefore, facilitates the transfer into extracting solvent. Omitting the chelation step required for the extraction of chromium (VI) has not prevented chromum from being extracted, priving that a solvent-soluble form of chromium was present in the analyte materials. In the second change, the EPA chromium (VI) determination method was used in parallel on replicate sample groups, one of which had been treated with a powerful chromium (VI)-reducing agent. Spiked samples of several kinds also were analyzed to demonstrate that hexvalent chromium was eliminated by this reductant. Yet, significant chromium from only the waste materials still was extractable, again indicating that it was not hexavalent chromium but a solvent soluble chromium (III) compounds, including a chrome soap and a complex, and lagoon sludge water-immisciblephase with a high content of chromium (III) were introduced into water and extracted according to method 7197 and the two differentiation procedures. All three kinds of samples yielded high to complete extraction recoveries of chromium, regardless of the technique. In conclusion, the results of the aforementioned experiments indicate that the EPA chelation/extraction method for determining hexavalent chromum can definitely give false positive or erroneously high values when used on some tannery wastes. |
| En ligne : |
https://drive.google.com/file/d/1O4nZWr48MagDhCGX1e2H46XSZZIgl5Rw/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8726 |
in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. LXXXV (Année 1990) . - p. 363-375
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Determination of CrVI) in tannery waste by the chelation-extraction method in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. LXXXV (Année 1990)
