The solution chemistry and statistical modelling of the O$ sb2$-CaCl$ sb2$-HCl leaching of a high-grade arseniferrous uranium ore (Key Lake, N. Saskatchewan) were studied with the objective of optimizing the co-extraction of uranium and radium. To this end, two types of experiments were carried out: (a) those designed to study arsenic speciation under simulated U-leaching conditions, with the use of model arsenide minerals, namely niccolite (NiAs), rammelsbergite (NiAs$ sb2$) and gersdorffite (NiAsS); and (b) statistically designed tests involving actual leaching of samples of the Key Lake ore. / Niccolite and rammelsbergite were found to yield H$ sb3$AsO$ sb3$ in solution as oppossed to gersdorffite, which was found to yield H$ sb3$AsO$ sb4$. H$ sb3$AsO$ sb3$ was found to be metastable in the Fe$ sb2$(SO$ sb4) sb3$ leaching system, while in the FeCl$ sb3$ and pressure (O$ sb2$) leaching systems, further oxidation to H$ sb3$AsO$ sb4$ was observed to take place at relatively slow rates. A mechanism has been advanced to account for the latter slow oxidation of H$ sb3$AsO$ sb3$ to H$ sb3$AsO$ sb4$. Finally, it was concluded that the formation of As(III)/As(V) in oxidative acid leaching is independent of the prevailing suspension redox potential which, in turn, renders impractical the possible stabilization of As(III) via potential control. / The solubility of RaSO$ sb4$ in HCl-MeCl$ sb{ rm x}$ leaching media was quantitatively established by employing the "reduced activity coefficient" method. The estimated solubility profiles clearly demonstrated the effectiveness of CaCl$ sb2$ in solubilizing radium as oppossed to other monochloride salt additions. / Finally, optimization of the co-extraction of U and Ra was attained with the use of a computer-aided response surface methodology. An incomplete three-level, four-variable factorial design (Box-Behnken) was applied in the region: 0.33 kg/L $ leq$ d$ sb{ rm s}$ $ leq$ 0.99 kg/L; 0.5N $ leq$ (HCl) $ sb{ rm o}$ $ leq$ 1.5 N; 1.5 M $ leq$ (CaCl$ sb2 rbrack sb{ rm o}$ $ leq$ 3.5 M; and 2 hrs $ leq$ Time$ leq$ 6 hrs. Temperature and oxygen pressure were kept constant at 68$ sp circ$C and 510 kPa (75 psi), respectively. Uranium and radium were found to dissolve simultaneously and rapidly (99% co-extraction in 2 hrs). Effective reduction of radioactivity levels from 10,000 pCi/g Ra$ sp{226}$ down to 160 pCi/g has been achieved in a single-stage batch process, thus making possible the production of environmentally innocuous tailings.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28405 |
| Date | January 1988 |
| Creators | Kondos, Peter Dimitri |
| 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: 000909932, proquestno: NL52468, Theses scanned by UMI/ProQuest. |
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