Galvanic Interaction Studies on Sulphide Minerals

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Abstract
Galvanic interactions occurring when two sulphide minerals are in contact with each other have been investigated by electrochemical techniques for pairs of the following: pyrite, chalcopyrite, galena and sphalerite. Combination potentials of pyrite electrodes in galvanic contact with a second sulphide were significantly lower than the rest potential of pyrite alone. This suggested electron transfer to pyrite which makes it more reducing. Similar results were obtained with the chalcopyrite galena couple, chalcopyrite becomes more reducing by galvanic interaction with galena. Galvanic interactions are weakened in nitrogenated water due to the lower activity of dissolved oxygen. This is shown by: (a) much smaller drop in potential when pyrite is in galvanic contact with another sulphide in nitrogenated water; (b) Zn2+ ions released into solution: dissolution of Zn2+ ions in sphalerite pyrite mixtures is decreased in nitrogenated water; and (c) xanthate uptake at pyrite-sphalerite mixtures is increased by appropriate use of nitrogen. In aerated water the flotation behaviour of a mineral in a mineral mixture differs significantly from that of the single mineral. The use of nitrogen promotes pyrite flotation from the mixture. A model of galvanic coupling and the role of N2 are discussed.

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