Abstract

The presence of enargite (Cu3AsS4) in porphyry copper deposits is an important matter as this mineral shows good flotability in the presence of the thiol collectors used in the flotation copper sulfides thus contaminating the final concentrate. Besides a relevant problem in Chilean mining is the scarcity of water resources so the use of seawater has become a feasible solution. The flotation behavior of copper sulfides and molybdenite in seawater was previously studied but there are no systematic studies related to the flotation of enargite using seawater. The objective of this work is to study the behavior of enargite in the process of flotation using seawater and to compare the flotation of enargite and chalcopyrite in this aqueous medium, The results indicate that the recovery of enargite is strongly depressed at pH > 9 in the process of flotation using seawater, behavior that can be explained in the first place by the adhesion of the hydrolysis products of magnesium on the surfaces of the enargite particles. The analyses of the Pourbaix diagrams for the As-Ca and As-Mg systems also suggest that the enargite depression in seawater observed at pH > 9 can not only be related to the adsorption of hydroxo complexes of magnesium and calcium, but also to the interaction of these metals with oxidized arsenic species such as arsenate and arsenite. As these compounds are hydrophilic in nature they reduce enargite recovery. Pretreatment of seawater before flotation to remove most of the calcium and magnesium present through the precipitation of hydrolyzed complexes of these cations is a suitable way to improve enargite recovery at pH > 9.