<Original Papers>Flotation of Copper-Nickel Sulphide Ores from the Jinchuan Mine, China (I) : On the Effects of Pulp Temperature, pH Values and Sodium Hexametaphosphate

Copper-nickel sulphide ores from Jinchuan mine in China contain mainly pentlandite, chalcopyrite, pyrrhotite and gangue minerals consisting of serpentine, olivine and pyroxyne. In the flotation of pentlandite and chalcopyrite, these gangue minerals, containing particularly serpentine, lead to poor separation. At present, the bulk concentrates of nickel-copper are low grade due to the high content of magnesium. In the smelting, both higher grade of nickel-copper and lower grade of magnesium in the bulk concentrates are required. The favored conditions concerning the temperature of pulp, pH value and the addition of sodium hexametaphosphate in the flotation process were investigated. The results obtained are as follows ; (1) The floatability of pentlandite with amylxanthate is poor at the natural pH of 9.4. On the other hand, it increases appreciably at pH below 6. Significant amounts of sulphric acid, however, are necessary to make the pulp acidic because of the large amounts of serpentine and other magnesium minerals in the ores. (2) The floatabilities of pentlandite and chalcopyrite are highly increased by addition of sodium hexametaphosphate at the natural pH of 9.4. The transformation of the insoluble magnesium precipitate from a colloidal magnesium hydroxide, which adheres to the surface of sulphide minerals, to a hydrophilic form, accounts for the increased floatability. The same behavior was detected with sodium carbonate, potassium fluorite, sodium phosphate and sodium arsenate which make insoluble compounds with magnesium ions. (3) The floatability of pentlandite is influenced by the temperature of the pulp at natural pH. Its floatability increases at pulp temperatures below 10°-15℃, and decreases at pulp temperature above 20℃