Effect of Eh and pH on the flotation of enargite using seawater

Abstract

The presence of enargite in porphyry-copper deposits is an important matter as this sulfosalt displays good floatability in the presence of the collectors which are usually used in the flotation of copper sulfides, thus it readily floats and contaminate the copper concentrates. Scarcity of water resources is a relevant problem in the Chilean mining industry and the use of seawater in the mineral processing plants is today a feasible solution. The flotation behaviors of copper sulfides and molybdenite in seawater was studied to some extent, but the enargite behavior in this aqueous medium has seldom been investigated. The objective of this work was to study the flotation behavior of enargite in seawater under different pulp electrochemical potentials (Eh) and pH. The independent effects of calcium and magnesium were also evaluated. The experimental results show that enargite flotation in seawater is depressed at both reducing and oxidizing conditions at pH = 9. At pH = 10.5 enargite is strongly depressed to values even below 20% at the whole range of Eh studied which may be explained by the adhesion of magnesium hydroxo-complexes to the enargite surfaces rendering it hydrophilic. The depressing effect of calcium on enargite flotation is stronger than the depressing effect of magnesium, although calcium concentration in seawater is lower. This conclusion may be related to the presence of highly stable compounds such as hydrophilic calcium arsenates on the enargite surface.