Document Type Doctoral Thesis Author Vermaak, Matthys Karel Gerhardus email@example.com URN etd-10132005-105623 Document Title Fundamentals of the flotation behaviour of palladium bismuth tellurides Degree PhD (Metallurgical Engineering) Department Materials Science and Metallurgical Engineering Supervisor
Advisor Name Title Prof P C Pistorius Keywords
- Great Dyke and Pd-bearing bismutho-tellurides
- precious metal ores
- platinum flotation
- flotation kinetics
- particle size
- ore mineralogy
- froth flotation
Date 2005-05-08 Availability unrestricted AbstractPrevious mineralogical investigations (QemSCAN) performed on all effluent flotation streams of Mimosa mine (Zimbabwe) indicated the presence of appreciable amounts of platinum group minerals (PGMs), which are not recovered. Most, generally in excess of 70%, of the liberated PGMs in these streams belonged to the Pt-Pd-Bi-Te class in all the samples investigated.
In the first part of this work, electrochemical investigations, electrochemically-controlled contact angle measurements and Raman spectroscopy have been employed to investigate the interaction of ethyl xanthate with Pd-Bi-Te and PtAs2. Impedance measurements showed lower capacitance values in solutions containing KEX indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction, hence the formation of dixanthogen on the surface is possible.
Electrochemically controlled in situ Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. The result of this investigation has shown dixanthogen to be present on both the minerals (PtAs2 and Pd-Bi-Te) when the surfaces are anodically polarized. Chemisorbed xanthate could be identified within 120 seconds yielding a hydrophobic surface as indicated by electrochemically-controlled contact angle measurements. Maximum contact angles of 63o were measured in the case Pd-Bi-Te. As a result the mineral surface is expected to be hydrophobic and a lack of collector interaction with the mineral is not the reason for low PGM recoveries experienced.
Secondly, the flotation recovery of synthetically prepared Pd-Bi-Te was compared with that of chalcopyrite (a typical fast-floating mineral) and pyrrhotite (a typical slow-floating mineral), with microflotation tests. These indicated Pd-Bi-Te to be a fast-floater with flotation rates exceeding that of chalcopyrite. Predicted flotation rate constants (from the Ralston model) were significantly lower for small particles (with diameters similar to those lost to the effluent streams) compared with those of particle with intermediate sizes. This supports the suggestion that losses to effluent streams are caused by particle size effects.
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28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access 00front.pdf 119.07 Kb 00:00:33 00:00:17 00:00:14 00:00:07 < 00:00:01 01chapter1.pdf 95.70 Kb 00:00:26 00:00:13 00:00:11 00:00:05 < 00:00:01 02chapter2.pdf 699.59 Kb 00:03:14 00:01:39 00:01:27 00:00:43 00:00:03 03chapter3.pdf 95.56 Kb 00:00:26 00:00:13 00:00:11 00:00:05 < 00:00:01 04chapter4.pdf 494.90 Kb 00:02:17 00:01:10 00:01:01 00:00:30 00:00:02 05chapter5.pdf 765.26 Kb 00:03:32 00:01:49 00:01:35 00:00:47 00:00:04 06chapter6.pdf 88.90 Kb 00:00:24 00:00:12 00:00:11 00:00:05 < 00:00:01 07chapter7.pdf 102.23 Kb 00:00:28 00:00:14 00:00:12 00:00:06 < 00:00:01 08references.pdf 125.95 Kb 00:00:34 00:00:17 00:00:15 00:00:07 < 00:00:01 09appendices.pdf 1.11 Mb 00:05:08 00:02:38 00:02:18 00:01:09 00:00:05