The subject of this work is gallium extraction from sulphate solutions--an additional source of this metal from hydrometallurgical zinc production--with organophosphorus acid reagents: di-2-ethyl hexyl phosphoric acid (D2EHPA) and OPAP, a mixed extractant consisting of mono- and di-octyl phenyl phosphoric acids. Extraction proceeds via cation-exchange and Ga$ sp{3+}$ is the reacting species. Gallium is extracted with D2EHPA mostly as GaR$ sb3$ - HR. The results for OPAP suggest existence of four reactions, which form GaM$ sb3,$ GaM$ sb2$D, GaMD$ sb2,$ and GaD$ sb3;$ this explains and allows prediction of behaviour over a wide range of OPAP compositions. Sulphate complexation causes decrease in concentration of the reacting species, and thus lower $D sb{ rm Ga}$ values and extraction rates. Prior knowledge on gallium aqueous complexes is used, and an algorithm developed, to allow quantitative prediction of complexation effects on extraction. The model of mass-transfer with chemical reaction, verified with several known criteria for reaction site determination, describes well the kinetic data for the Ga-D2EHPA system. The model is further developed to account for the stronger acidity and the monomer/dimer equilibria typical for the kind of extractants used. A detailed reaction mechanism is proposed and the first organic ligand addition is found as rate-limiting. The model parameters, estimated from extraction kinetic data, are reasonable, when compared with those obtained for other metals elsewhere. The model's predictions agree with the results from stripping kinetics; the equilibrium conditions (zero rate) can also be satisfactorily predicted, as found by comparisons with the equilibrium data. Ga-D2EHPA and Ga-OPAP systems are compared with an emphasis given to the potential for metal separation; the importance of the ligand exchange rate constant is illustrated with the example of Ga and Al extraction/stripping and their separation based on different rates with
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70338 |
| Date | January 1991 |
| Creators | Mihaylov, Indje O. (Indje Ognianov) |
| 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: 001270199, proquestno: AAINN74868, Theses scanned by UMI/ProQuest. |
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