Papers by Keyword: Chalcopyrite

Abstract: The thermophilic archaean, Acidianus brierleyi, was examined for its feasibility to bioleach copper from a low-grade chalcopyrite ore (1.15 % copper, 20.4 % iron and 2.63 wt% sulfur) at 65°C and pH 1.8-2.5. The chalcopyrite leaching was markedly accelerated in the presence of A. brierleyi, and an extremely high 80% leaching of copper in the low-grade ore (25-38 μm particles) was achieved in 14 days in a batch stirred reactor. By comparison, the leaching of iron was very slow and only a slight 5 % iron was leached in 14 days in the presence or absence of A. brierleyi. In other words, A. brierleyi selectively leached chalcopyrite while magnetite leaching by A. brierleyi was negligible. Moreover, bioleaching of the low-grade ore (53-75 μm particles) yielded 55% copper recovery after 20 days of operation in a column reactor. The good results for the copper bioleaching in the column reactor are very similar to those in the stirred reactor. These results lead to the conclusion that the thermophile bioleaching with A. brierleyi is attractive as an economical and environmentally friendly process for good copper extraction from low-grade chalcopyrite ore.

Abstract: Bioleaching of copper sulfides is catalyzed by iron-and sulfur-oxidizing acidophilic microorganisms attached to the mineral surface forming a biofilm. However, the link between copper sulfides bioleaching and biofilm formation is not yet fully understood. Understanding the factors that are limiting the bioleaching kinetics for different copper sulfide minerals through exhaustive mineralogical analysis of the mineral surface with concomitant biofilm formation during the leaching process will deliver new process conditions with enhanced kinetics and higher copper recovery. In this work we have developed and standardized a reproducible flow cell method able to mimic heap/dump bioleaching laminar flow conditions to study the mineralogical dynamics by advanced mineralogical analysis including QEMSCAN and SEM-EDS coupled to biofilm formation analysis. Based on this method, the bioleaching mineralogical dynamics of primary copper sulfides (enargite (Cu₃AsS₄), chalcopyrite (CuFeS₂) and bornite (Cu₅FeS₄)) have been determined in the presence of biofilm formation. Supported by the observed mineralogical dynamics, different mechanisms of dissolution for bioleaching were observed as well as selective biofilm formation over the mineral surface, showing enhanced conditions for copper recovery.

Abstract: The objective of this study is to improve the understanding of copper sulfides dissolution and to use this knowledge for optimization of process parameters for commercial application of electrochemical bioleaching of chalcopyrite concentrates in stirred bioreactors. From the results of this study, the importance of the oxidation reduction potential (ORP) on the catalytic interaction between chalcopyrite and pyrite can be pointed out as the main parameters for successful bioprocessing of chalcopyrite concentrates. Under these conditions, the optimization of the average particle size of feed (D80) and adjusting the ORP in the range between 400-450 mV are important criteria for increasing the electrochemical bioleaching rate of chalcopyrite concentrates. It seems that the main reason for the increased copper recovery could be the control and prevention of chalcopyrite passivation resulting from improved galvanic interaction between copper sulfide minerals, here especially chalcopyrite and pyrite in the selected ORP range and the right particle size distribution of feed. At optimum conditions, the copper extraction from chalcopyrite flotation concentrate during 7 days of continuous electrochemical bioleaching operations in stirred tanks was about 95%, which should be high enough to justify the process economically.

Abstract: Bioleaching experiments were used in this experiment to study the interaction between marmatite and chalcopyrite. In the sterile system, the copper extraction rate of single chalcopyrite was only 20%, much lower than the copper extraction rate of L. ferriphilum system, which is 95%. The addition of L. ferriphilum can improve the copper extraction rate to a substantial level. In both the sterile and L. ferriphilum system, the single chalcopyrite got a higher copper extraction rate than the mixture minerals of chalcopyrite and marmatite, and with the increase of marmatite, the copper extraction rate decreased. So marmatite may inhibit the dissolution of chalcopyrite. The reason may be that the redox potential of mixture mineral was not in the optimum range.

Abstract: Various methods of controlling redox potential (ORP) with electrochemical bioreactor and others have been investigated to increase copper extraction of chalcopyrite in bioleaching,but less attention has been paid to reducing ferric to ferrous ions. Therefore, in this work, the redox potential of chalcopyrite bioleaching system in the presence of mixed moderately thermophiles containing Leptospirillum. ferriphilum, Acidithiobacillus. caldus and Sulfobacillus. thermosulfidooxidans has been controlled by pyrite. It was found that at a constant pH of 2.0, the addition of pyrite can reduce ferric to ferrous ion to a large extent, and the lower ORP values can be obtained. Bioleaching experiments indicated that the time for adding pyrite caused different bioleaching behaviors of chalcopyrite. The high copper extraction can be obtained by added pyrite at a low ORP values (<420 mV vs. Ag/AgCl). The XRD tests and SEM images showed that the amounts of formed jarosite increased as the pyrite addition, and the loose and porous jarosite can be found at low ORP values.

Abstract: Chemical element analysis and X-ray diffraction (XRD) analysis showed that the two chalcopyrite minerals were of high purity. A mixed culture of moderately thermophiles was used for chalcopyrite bioleaching at 45°C and the copper recovery of chalcopyrite (a) and chalcopyrite (b) was 66.1% and 21.4%, respectively, after 19 days of leaching. Bioleaching behavior of the two different chalcopyrite samples was studied through comparing the lattice parameter and grain size of chalcopyrite. It was shown that lattice parameter and grain size are not the key factors affecting the leaching of chalcopyrite. The corrosion current density of chalcopyrite (a) calculated through Tafel curves was 1.149 μA/cm², while that of chalcopyrite (b) was only 0.5696 μA/cm². The higher corrosion current density suggested that chalcopyrite (a) can be more easily dissolved than chalcopyrite (b).

Abstract: In this work, we present an Electrochemical Impedance Spectroscopy (EIS) study using a carbon paste electrode modified with chalcopyrite (CuFeS₂) containing 50 wt% of the mineral (particle size < 38 μm) and graphite (particle size < 20 μm) in naturally aerated salt acid solutions (pH 1.8) without and with the addition of 0.100 mol L^-1 of ferrous ions. The aim was to evaluate the influence of the solution potential on the behavior of chalcopyrite electrode in the presence and absence of iron (II) ions. Additionally, we evaluated the influence of the bacteria Acidithiobacillus ferrooxidans in the system containing iron (II) ions without applying potential. Therefore, EIS was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The results showed that the combination of iron (II) ions with the imposition of low potential values (0.100 Fe²⁺ ions with +0.300 V/Ag|AgCl|KCl_3mol/L) activates the chalcopyrite surface and enhances the copper recovery.

Abstract: In an attempt to investigate the use of bacteria and their metabolites as bioflotation reagents for environmentally friendly mineral processing, laboratory cell flotation tests were carried out using copper sulfide ores bearing a high content of pyrite, which were mixed with a biosurfactant-producing mixotrophic bacterium as bioflotation reagents. The interaction of bacterial cells and their metabolic products with the sulfide ores resulted in the alteration of the surface chemistry of both ores and bacterial cells as evidenced by FTIR and SEM-EDS observations as well as surface tension and contact angle measurements. The change in the surface properties of the sulfide ores in turn enabled the bacterium to function as flotation bioregeants in the flotation of copper sulfide ores as a function of bacterial cell concentration, conditioning time, flotation time and pH. Overall, the bacterium and its metabolites as bioreagents yielded flotation recoveries which might be attributed to the multi-function of the bacterium as depressant, collector and frother. Thus, the bacteria tested in this study could potentially be used as flotation bioreagents, providing an alternative to conventional flotation reagents.

Abstract: JOGMEC has been carrying out the study on primary copper sulfide ores leaching for recovering copper economically and efficiently by heap leaching. In our study, we have been using the primary copper sulfide ore produced in an IOCG deposit. The ore is characterized by high iron content and high acid consumption in leaching. For the optimization of the leaching, the conditions such as ore size, agglomeration, pH and irrigation rate of leaching solution were examined with column leach tests. The best result was over 80 % extraction of copper in 150 days with leaching solution of 1 M sulfuric acid and temperature of 45 °C. In this experiment, the fines of the ore sample were removed before putting it into the column to keep the permeability of the ore bed. In these column leach tests, the Fe²⁺/total-Fe ratio of PLS decreased gradually by the activity of naturally grown iron-oxidizing bacteria. The bacteria in PLS, which have the ability of iron-oxidizing and sulfur-oxidizing, were identified by next-generation sequencing as Acidithiobacillus caldus and Sulfobacillus thermosulfidooxidans. We also carried out bench-scale tests with about 200 tons of the primary copper sulfide ores. Iron-oxidizing and sulfur-oxidizing bacteria were identified in the leaching solution as same with column leach tests. It is considered that the bacteria worked in the leaching solution and on the surface of the ores.

Abstract: The experiment focused on the effect of pyrite on the dissolution of the ore from Saindak copper mine in Pakistan. The MLA results showed that the ore mainly consisted of chalcopyrite, which was associated closely with pyrite. The bioleaching process and galvanic promotion experiments of pyrite on the copper extraction were investigated. The data revealed that copper recovery rate could be up to 97.8% after the bioleaching process by extreme thermophilic acidophilic organisms for 30 days at 65 ^OC. The temperature and redox potential were the controlled factors to recover copper from the Saindak mineral. The phylogenetic analyses of 16S rRNA gene fragments revealed that organisms related to Metallosphaera cuprina strain Ar-4 and Sulfolobus sp. HB59 were most dominant. Pyrite could accelerate the dissolution of chalcopyrite as one galvanic assistant substance, which would be strengthened by elevating the temperature or in the presence of microorganisms.