Abstract
Copper-molybdenum grades of important mining deposits have progressively decayed, which is associated with high levels of clay minerals which affect froth flotation. The depressing effect of clay minerals on copper sulfides was previously reported but there are no systematic studies on the effect on molybdenite flotation in seawater. The objective of this work was to study the effect of kaolinite on molybdenite flotation in seawater and to evaluate the use of sodium hexametaphosphate (SHMP) as dispersant. The results of this work show that kaolinite depresses molybdenite flotation which is more significant in seawater at pH > 9. All the experimental data validate the hypothesis that kaolinite covers molybdenite, reducing its flotation recovery. The depressing effect of kaolinite on molybdenite flotation in seawater is enhanced by the magnesium and calcium hydroxo complexes at pH > 9, which induce heterocoagulation between kaolinite and molybdenite, thus reducing recovery. The attachment of the positively charged hydroxo complexes of magnesium and calcium to the molybdenite and kaolinite surfaces is diminished by SHMP. This reagent increases the repulsive forces between molybdenite and precipitates and as a result, molybdenite becomes more hydrophobic and recovery increases.
Highlights
Copper-molybdenum grades of important mining deposits around the world have progressively decayed during the last few decades, which is generally associated with high concentrations of phyllosilicates
When these authors used seawater, chalcopyrite was depressed at pH > 9 which was explained by the compression of the electrical double layer (EDL) and by the action of magnesium precipitates that induce a strong interaction between kaolinite and chalcopyrite
The results presented in this work show that kaolinite affects molybdenite flotation which is more significant in seawater at pH > 9, and that sodium hexametaphosphate (SHMP)
Summary
Copper-molybdenum grades of important mining deposits around the world have progressively decayed during the last few decades, which is generally associated with high concentrations of phyllosilicates. Clay minerals are the most common phyllosilicates found in copper-molybdenum porphyry deposits [1]. These types of soft mineral species are usually dispersed in mineral slurries as fine particles generating the conditions for non-Newtonian behavior [2], which affects the entire mineral processing chain, i.e., milling, froth flotation, thickening, and dewatering [3,4,5,6,7]. The efficiency of flotation of copper sulfides is severely affected by clay minerals [3,4,8]. Molybdenum is a strategic metal which is commonly found associated with copper in porphyry copper deposits, and molybdenite (MoS2 ) is the main molybdenum-containing mineral, which is characterized by its natural hydrophobicity, it readily floats together with copper sulfides. The effect of clay minerals on molybdenite flotation has seldom been studied
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