Abstract
Copper is a metal with a great economic interest and about 70% is found in nature in chalcopyrite form (CuFeS2). However the chalcopyrite dissolution is a challenge for industries as well as researchers because of its slow dissolution kinetics. The control of redox potential is one factor that can help in this drawback. This study was undertaken to evaluate the role of redox potential on chalcopyrite bioleaching by addition of ferrous ions. Acid leaching with addition of ferrous ions promoted high dissolution of chalcopyrite by the maintenance of low redox potential (420 mV/Ag/AgCl). On the other hand, the copper dissolution in bacterial systems showed low copper recovery (610 mV/Ag/AgCl). XRD of solid residues showed in abiotic conditions the formation of elemental sulfur, jarosites and a significant decrease on chalcopyrite’s peaks. In bacterial conditions, only jarosites was detected as new crystalline phase. SEM analysis confirmed the results obtained by XRD. In general, the results showed conclusive evidence that the maintenance of low redox potential and the addition of ferrous ions have positively influenced the copper recovery and confirmed the literature data, which indicate a critical potential range where chalcopyrite leaching is more favorable.
Highlights
Chalcopyrite is the primary copper mineral for production of copper metal
Leaching experiments pH, redox potential, ferrous ions and total iron concentrations were monitored throughout the experiment
Several other authors[24,25,26] have focused only on a critical redox potential range (400-450 mV) over which chalcopyriteleaching is hindered. This current study showed that the control condition tested was the system that reached the lowest redox potential value and the lowest copper recovery
Summary
Chalcopyrite is the primary copper mineral for production of copper metal. It is known to be one of the most stable copper minerals due to its structurally face-centered tetragonal lattice and for responding poorly to hydrometallurgical processes when compared to copper oxides ores[1,2].Slow dissolution rates of chalcopyrite have been attributed to a possible blockage by a superficial layer whose formation and action mechanisms on chalcopyrite are still quite contradictory in the literature. Chalcopyrite is the primary copper mineral for production of copper metal. It is known to be one of the most stable copper minerals due to its structurally face-centered tetragonal lattice and for responding poorly to hydrometallurgical processes when compared to copper oxides ores[1,2]. Córdoba et al.[3] associated this layer formation with high concentration of ferric ion, high redox potential values, potentiating jarosite precipitates formation (XFe(SO4)2(OH)[6] where X = K+, NH4+, Na+ or H3O+) and blocking chalcopyrite surface. Studies have already discussed that the formation of a compact sulfur layer, ironbearing precipitates or jarosites has been responsible for covering chalcopyrite surface and leading to a slow and/or incomplete copper extraction[4,5,6]. It is noteworthy that the formation of jarosites is favored in media with high values of redox potential, such as Eclética Química Journal, 42, 2017
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