Abstract

Scarcity of fresh water, particularly for operations situated in desert areas, has forced the coppermolybdenum mining companies to look for new sources of water such as seawater. The use of this saline aqueous medium in the process of flotation leads to some important effects on the efficiency of this process. Besides, copper grades of large copper deposits have constantly decreased during the last decades, which is typically associated to high concentrations of clay minerals in the ores which is known to negatively affect the flotation process. The objective of this research was to evaluate the effect of kaolinite on the floatability of molybdenite at different pH conditions, using two types of solutions (0.01M NaCl solution and seawater). Floatability of molybdenite particles was assessed through micro-flotation tests in a 150cm3 Partridge-Smith glass cell and using nitrogen (N2) at a flowrate of 20cm3/min, for a total flotation time of 10 minutes. Flotation feed was prepared mixing known amounts of molybdenite with particles of kaolinite. The results of this study indicate that molybdenite floatability slightly decreased under the presence of fine particles of kaolinite when conventional water was used in the tests. However, in seawater the negative effect of kaolinite was more relevant, in particular at pH>9, which suggests that the presence of cations in solution intensify the phenomenon of heterocoagulation between fine kaolinite particles and molybdenite (slime coating). It is assumed that the stronger depressing effect of kaolinite at pH>9 could be related to the formation of hydroxy-complexes of magnesium and calcium.