The selective flotation of enargite from other copper minerals — a single mineral study in relation to beneficiation of the Tampakan deposit in the Philippines

The floatability of enargite (3Cu2S.As2S5) has been determined as a function of pulp potential to establish whether the flotation behaviour of the mineral differs sufficiently from that of other copper minerals thus offering the prospect of rejecting arsenic from the Tampakan ore by potential control during flotation.The results of a single mineral flotation study reveal that a threshold potential exists above which enargite floats and below which it does not. On the standard hydrogen electrode (SHE) scale this potential is about − 75 mV SHE at pH 8 and about − 25 mV SHE at pH 11. By contrast, chalcopyrite (CuFeS2) has a threshold potential of about + 160 mV at pH 8 and chalcocite (Cu2S) has a threshold potential of about − 155 mV SHE at pH 11. In addition, chalcocite and cuprite (Cu2O), but not enargite and chalcopyrite, have an upper limiting potential at pH 11 (> + 270 mV SHE) above which their floatabilities are depressed.On the basis of these results it was concluded that the selective separation of enargite from other copper minerals would be enabled by controlling the flotation pulp potential. Specific flotation separations are as follows.
• Copper sulphides such as chalcocite and copper oxides such as cuprite could be floated from enargite at pH 11 after setting the potential to about − 125 mV SHE.
• Enargite could be floated from copper–iron sulphides such as chalcopyrite at pH 8 or pH 11 after setting the potential to about 0 mV SHE.
• Enargite could be floated from copper sulphides such as chalcocite and from copper oxides such as cuprite at pH 11 after setting the potential to about + 290 mV SHE.A conceptual flow sheet for arsenic rejection at Tampakan, based on these findings, is presented and discussed in this paper.