Abstract
Pyrite particles, having framboidal/altered texture, are known to significantly affect pulp chemistry and adversely affect flotation performance. Therefore, the main objectives of this study were to demonstrate influence of pyrite mineralogy on the flotation of copper (sulphidic) ores and develop alternative conditions to improve the performance. Two copper ore samples (Ore A and Ore B) having different textural/modal mineralogy and flotation characteristics were taken from different zones of the same ore deposit. Ore B contained framboidal pyrite and altered pyrite/marcasite, which is considered the main reason for the low flotation performance in both copper and pyrite flotation sections of the process plant. Flotation tests were conducted under different conditions using the two ore samples and a 50:50 blend. The results showed that Ore A could be concentrated under the base conditions, as applied in the existing flotation plant. On the other hand, Ore B did not respond to the base conditions and a copper recovery of only 5% could be obtained. Besides, blending Ore B with Ore A negatively affected the flotation behavior of Ore A. An alternative flotation chemistry was applied on Ore B using Na2S for surface cleaning and Na-Metabisulfite (MBS) for pyrite depression in the copper flotation stage. The surface cleaning reduced the rate of oxidation of the framboidal pyrite in Ore B. As a result, the copper recovery could be increased to 52% Cu for Ore B, and 65% for the mixed ore sample.
Highlights
Pyrite (FeS2 ) is the most abundant sulfide mineral and usually occurs both as a primary and secondary mineral according to its genesis
Two copper ore samples (Ore A and Ore B) having different textural/modal mineralogy and flotation characteristics were taken from different zones of the same ore deposit
Ore B contained framboidal pyrite and altered pyrite/marcasite, which is considered the main reason for the low flotation performance in both copper and pyrite flotation sections of the process plant
Summary
Pyrite (FeS2 ) is the most abundant sulfide mineral and usually occurs both as a primary and secondary mineral according to its genesis. Pyrite is widespread in hydrothermal veins, modern and ancient sedimentary (volcano, exhalative) rocks, contact metamorphic deposits/rocks and as an accessory mineral in igneous rocks [3]. The genesis of pyrite has been considered as one of the main causes of variation in surface chemical characteristics and, thereby, of the differences in their floatability [4]. Contact angle measurements of different types of pyrite showed a significant relationship between the origin of pyrite and its wetting characteristics. Flotation characteristics of pyrite are influenced by morphology, crystallography, and the presence of impurities in the crystal structure [5]. The marcasite mineral (FeS2 ), the polymorph of pyrite, has different crystallography and stability and, different flotation behaviour than that of pyrite, even when they exist in same deposits [3,6]
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