The aim of this work was to devise and investigate a solvent extraction system for rhodium, from aqueous chloride solutions, having potential industrial applicability. The extractant investigated was Kelex 100, a commercially available derivative of 8-hydroxyquinoline. Ultimately, two different systems were developed. Both are based on an initial complexation reaction between the aqueous rhodium chloride complexes, (RhCl$ rm sb{6-n}(H sb2O) sb{n} rbrack sp{(3-n)-}$ and stannous chloride, referred to as the activation stage, but the two systems use a different Sn:Rh molar ratio. In both cases, the Rh-Sn complexes, either (Rh(SnCl$ sb3) sb5 rbrack sp{4-}$ or (RhCl$ rm sb3(SnCl sb3) sb3 rbrack sp{3-},$ respond well to extraction with Kelex 100. One of the main differences between the two systems is in the stripping medium which is used to transfer the rhodium from the loaded organic phase back into an aqueous phase. In the case of the high Sn:Rh ratio feeds, the stripping stage is based on sulfuric acid, whereas in the case of low Sn:Rh ratio feeds, the rhodium is stripped from the organic phase using a sulfite containing hydrochloric acid solution. / The two systems were characterized in terms of their equilibrium and kinetic behaviour during all three stages; activation, extraction, and stripping. Activation was found to proceed either at room temperature or at elevated temperatures and the above-mentioned expected Rh-Sn complexes were identified through $ sp{119}$Sn NMR and Raman spectroscopy. The extraction stage was found to be quantitative for rhodium and it was also found to be very rapid, with contact times of less than five minutes sufficient for rhodium extraction. The extraction mechanism was determined to be ion-pair formation with the protonated Kelex 100 molecules at a stoichiometry such that the overall charge in the organic phase is neutral, i.e., three Kelex 100 molecules for (RhCl$ rm sb3(SnCl sb3) sb3 rbrack sp{3-}$ and four for (Rh(SnCl$ sb3) sb5 rbrack sp{4-}.$ / The stripping stages were the most problematic for both systems. In one case, the system was eventually abandoned due to limitations in the amount of rhodium which could be transferred to the sulfuric acid strip solution. For the low Sn:Rh system, reasonable rhodium transfer and concentration level were obtained. The rhodium complex in the strip solution has been proposed to be (RhCl$ rm sb2(SO sb3) rbrack sp{3-}.$ Strip solutions up to $4 times10 sp{-2}$M in rhodium concentration have been produced, from initial feed solutions having a rhodium concentration of about $4 times10 sp{-3}$M. Preliminary flowsheets are proposed for further refinement for both systems, although only the second system, the low Sn:Rh ratio system which uses sulfite stripping, is advocated for further development.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40321 |
| Date | January 1996 |
| Creators | Benguerel, Elyse. |
| Contributors | Demopoulos, G. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001536204, proquestno: NN19710, Theses scanned by UMI/ProQuest. |
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