Comparison of the Flotation of Enargite Using Fresh and Seawater

Chile is the world's largest copper producer which is mostly in the form of sulfides for which froth flotation is the most efficient concentration process. As a result a concentrate that contains high concentrations of copper sulfides such as chalcopyrite, chalcocite and enargite is obtained. In the last decades processing of ores containing high concentrations of enargite (Cu3AsS4) has continuously increased in Chile, which is related to the fact that ore deposits nawadays are more heterogeneous and complex. Enargite is a mineral that contains arsenic and its presence in the copper concentrates implies severe penalties. In addition, the shortage of fresh water has driven the search for new alternative sources of water, among which seawater has proved to be one of the most attractive. The objective of this research is to study the behavior of the enargite in the process of flotation using seawater, and at the same time to compare its behavior with the results obtained using conventional water. The study was carried thorugh micro-flotation tests using pure samples of enargite, at pH values ranging from 4 to 11, both in fresh and seawater. PAX and MIBC were used as collector and frother respectively. Micro-flotation tests were also done at different redox potential conditions so that the effect of the surface oxidation of enargite was evaluated in seawater. The results indicate that the recovery of copper from enargite is reduced in seawater compared to fresh water, in particular at the pH values close to those of the formation of the first hydroxy complexes of Mg and Ca. In general, the experimental data indicate that the floatability of enargite is strongly affected when seawater is used, in particular at oxidizing conditions. These results suggest that Mg2+ and Ca2+ ions contained in seawater interact with the surface of enargite forming hydrophilic species.