In that reef, base metal sulphide BMS minerals are commonly associated with PGMs and this has an effect on the way in which these minerals are concentrated by flotation Vermaak et al.
The present investigation has focused on studying the relationship between the flotation of sulphide minerals using xanthates as collectors and the electrochemical properties of the flotation system. The aim of this study was to investigate the extent to which there was a relationship between the electrochemical reactions occurring in this ore which could indicate the effectiveness of the flotation process.
The electrochemical reactions were studied by determining the redox potential changes occurring when various changes were made.
These were the length of the alkyl chain length of the xanthate collector, changing the pH or using various chemical reagents to change the potential of the system. It was found from the rest potential measurements, that collectors of different chain length have different extents of interaction with mineral surface. A greater interaction, which is indicated by a greater change in the mixed potential after addition of the collector, is considered to be indicative of a greater adsorption of the collector at the mineral surface.
It was hypothesized that this stronger adsorption by collectors of longer alkyl chain length would result in improved flotation performance. However, this was not observed to be the case and that was consistent with previous results on the relationship between the recovery of sulphide minerals in the Merensky ore and xanthates of different chain lengths. Thus it was shown that there was no correlation between the interactions between collectors of different alkyl chain lengths as determined through electrochemical studies and the flotation performance of valuable minerals under the tests conditions used.
Chimonyo, W. An investigation into the relationship between electrochemical properties and flotation of sulphide minerals. The rest potential observed for pyrite is, in fact more noble than that observed for any other sulphide mineral or synthetically prepared sulphide matte. The stoichlometry of the anodic reaction is of interest at potentials below 1.
The film formed on pyrite leads to the presence of a passive film in air and may possibly be adsorbed oxygen or an oxygen-sulphur compound. Separate experiments have shown that it is not rapidly reformed in the presence of ferric ions, and can be destroyed on anodized pyrite without loss of a visible ferric oxide tarnish. Oxidation experiments were conducted with a potassium ethyl xanthate solution under both oxygen bubbling and oxygen pressure atmospheres at room temperature.
Experiments in which ultraviolet measurements, due to xanthate ions, are involved show that the oxidation of xanthate under these conditions is rather slow, and the formation of oxidation products cannot be detected in ordinary flotation time. However, when pyrite is aerated in a solution containing xanthate, the formation of an oily film is observed.
The flotation of molybdenite seemed to be less influenced by xanthate than by kerosene, while that of chalcopyrite showed the opposite. In the alkaline solutions, unlike the acidic solutions, the intermediate products, iron oxide and hydroxides, are more stable. Services on Demand Journal. Marco, R. International Journal of Minerals Processing, vol. If pyrrhotite is oxidized by oxygen, it will produce ferrous iron and sulphate ions, similar to pyrite 24 :. In an alternative embodiment, the pulp may comprise a mixture of secondary copper, lead or zinc minerals and copper, lead or zinc sulphide minerals possibly in association with other elements of economic significance, eg other base metals, vanadium, and the separation from any gangue minerals may occur in the same step.
With xanthate, the oily film formed on such a mineral is identified as dixanthogen by means of infrared spectroscopy. Measurements of the redox potential of xanthate-dixanthogen systems were attempted to get a fundamental background on xanthate oxidation. The redox potential of xanthate-dixanthogen becomes more negative with an increase in the carbon numbers of alkyl radicals.
Without xanthate, pyrite shows 0. The reducing behaviour of xanthate would lead to lower rest potentials in this case.
The mechanism of dixanthogen adsorption on pyrite must satisfy all of these conditions. Assuming that adsorbed oxygen leads pyrite to the electrochemically passive state, the mechanism given by the following equation can be proposed,. The selective flotation of pyritic complex sulphide ores is occasionally very difficult.
The physical mixing of pyritic ore with other types of Cu-Pb-Zn-Fe complex sulphide ores sometimes results in a poor separation. The difficulties of selective flotation have been extensively examined as a function of activation of sulphide minerals with heavy metal salts formed by the oxidation of sulphide minerals.
The oxidation of complex sulphide ore is found to be enhanced with the association of pyrite. This is observed in a daily operation as expected from fundamental research.
As mentioned before, pyrite has the highest rest potential among all the sulphide minerals. The condition of pyrite in its natural state may be regarded as electrochemically passive. The cathodic treatment can only generate a clean pyrite surface, and this has a thermodynamically predictable active potential.
"Electrochemistry of Flotation of Sulphide Minerals" systematically covers various electrochemical measurements, especially electrochemical corrosive methods. The first € price and the £ and $ price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for. Germany, the.
Since pyrite can exist in both active and passive forms, we may anticipate that when pyrite is in galvanic contact-with other sulphide minerals, the corrosion of the other sulphide minerals will be enhanced if the pyrite is in a passive condition, as in air.
The elemental sulphur formation reaction in an acidic solution may be favorable as expected from potential-pH diagrams for metal-sulphur-water systems. It can also be seen in those potential-pH diagrams that elemental sulphur is rather stable in an acidic or weakly acidic solution. Thus the presumption that elemental sulphur formed on sulphide minerals, which are in electric contact with pyrite in flotation pulp, plays an important part in the flotatlon of complex sulphide ore seems plausible.