A dissertation submitted to the Faculty of Engineering, University of the
Witwatersrand, in fulfillment of the requirements for the degree of Mastel' of
Science in Engineering
Johannesburg 1998 / Impala's Minerals Processing Plant in the Rustenburg Area, South Africa, uses
flotation to beneficiate precious metal bearing ores from the Bushveld Complex.
Pyrrhotite is one of the sulphide minerals that is targeted but it is the least amenable to
current flotation conditions having the lowest recovery. Electrochemical techniques
(mixed potential measurements, cyclic voltammetry and current transient techniques)
were used to study the relevant reactions on the surface of pyrrhotite mineral
electrodes. Aspects investigated included the oxidation of the mineral in aqueous
alkaline solutions, activation by copper sulphate, kinetics of oxygen reduction and the
adsorption of isobutyl xanthate. Mixed potential measurements of mineral electrodes
were taken in batch flotation test work. In addition a novel qualitative measure of
hydrophobicity was investigated. The oxidised surface of pyrrhotite is likely to be
covered with iron hydroxides and a sulphur rich sub-lattice. No direct evidence was
found for the activation of pyrrhotite by copper sulphate in alkaline solutions. It was
shown however that activation could be achieved in mildly acidic media and that the
surface remained activated if subsequently exposed to alkaline conditions. When
achieved under acidic conditions activation was observed to enhance the degree of
interaction between the mineral and the xanthate collector. Also copper sulphate
appeared to aid the formation of a more hydrophobic surface (as indicated by the
hydrophobicity tests). Copper activation conducted in acidic media did not
significantly enhance the kinetics of oxygen reduction, a reaction seen as crucial to the
adsorption of xanthate. No evidence was found for the initial chemisorption of
xanthate onto the mineral surface. However evidence was found for the oxidation of
xanthate to dixanthogen at sufficiently anodic potentials. It Was concluded that the
relatively poor flotation performance of pyrrhotite could be combated by minimising
the extent of the oxidation, adding reagents as soon as possible before the mineral
becomes extensively oxidised and by removing surface hydroxides through lowering
the pH during conditioning. / MT2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/22047 |
| Date | January 1998 |
| Creators | Buswell, Andrew Mark |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (100 leaves), application/pdf |
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