Low-grade Chalcopyrite Ore Research Articles

A brief review on computer simulations of chalcopyrite surfaces: structure and reactivity.

Chalcopyrite, the world's primary copper ore mineral, is abundant in Latin America. Copper extraction offers significant economic and social benefits due to its strategic importance across various industries. However, the hydrometallurgical route, considered more environmentally friendly for processing low-grade chalcopyrite ores, remains challenging, as does its concentration by froth flotation. This limited understanding stems from the poorly understood structure and reactivity of chalcopyrite surfaces. This study reviews recent contributions using density functional theory (DFT) calculations with periodic boundary conditions and slab models to elucidate chalcopyrite surface properties. Our analysis reveals that reconstructed surfaces preferentially expose S atoms at the topmost layer. Furthermore, some studies report the formation of disulfide groups (S22-) on pristine sulfur-terminated surfaces, accompanied by the reduction of Fe3+ to Fe2+, likely due to surface oxidation. Additionally, Fe sites are consistently identified as favourable adsorption locations for both oxygen (O2) and water (H2O) molecules. Finally, the potential of computer modelling for investigating collector-chalcopyrite surface interactions in the context of selective froth flotation is discussed, highlighting the need for further research in this area.

The overlooked mechanism of chalcopyrite passivation

Chalcopyrite (CuFeS₂) is the world's main source of copper. Electrification of the global economy will rely on economically viable Cu dissolution from low grade chalcopyrite ores, but this process is particularly slow. The reason for this slow reaction has been in dispute for over 50 years. In this study, electrochemical analysis showed that n-type chalcopyrite is in an accumulation state when immersed in electrolyte, not in a depletion state as is commonly assumed. A leaching test and surface analysis confirmed the formation of a Cu-rich surface layer during oxidative leaching. In addition, a similar leaching test on covellite (CuS) showed leaching kinetics that were as slow as chalcopyrite. Ex-situ current-voltage analysis showed that the Cu-rich (covellite-like) product layer on the surface of chalcopyrite was a p-type semiconductor. Therefore, as leaching progresses, chalcopyrite transitions from a resistor to a diode. Three mechanisms for slow dissolution of chalcopyrite in acidic ferric media are proposed based on these tests: 1. The dielectric breakdown potential of chalcopyrite (0.7 V vs Ag/AgCl) is higher than what the ferric/ferrous redox couple can provide (0.5 V). 2. A chemically stable covellite-like surface layer prevents further Cu dissolution. 3. Rapid formation of a p-n junction on the leached chalcopyrite surface hinders the electrochemical process. We hypothesize that all three mechanisms together prevent the full dissolution of chalcopyrite under oxidative conditions at ambient temperature.

Investigation of Internal Classification in Coarse Particle Flotation of Chalcopyrite Using the CoarseAIRTM

This work introduces the CoarseAIR™, a novel system utilizing a three-phase fluidized bed and a system of inclined channels to facilitate coarse particle flotation and internal size classification. Internal classification in the CoarseAIR™ was investigated in a series of continuous steady-state experiments at different inclined channel spacings. For each experimental series, a low-grade chalcopyrite ore was milled to a top size of 0.53 mm and methodically prepared to generate a consistent feed. The air rate to the system was adjusted to determine the impact of the gas flux on coarse particle flotation and overall system performance, with a focus on maximizing both copper recovery and coarse gangue rejection. A new feed preparation protocol led to low variability in the state of the feed, and in turn strong closure in the material balance. Hence, clear conclusions were drawn due to the high-quality datasets. Inclined channel spacings of z = 6 and z = 9 mm were used. The z = 9 mm spacing produced more favourable copper recovery and gangue rejection. Higher gas fluxes of 0.30 to 0.45 cm/s had a measurable, adverse effect on the recovery of the coarser hydrophobic particles, while the gas flux of 0.15 cm/s delivered the best performance. Here, the cumulative recovery was 90%, and mass rejection was 60% at 0.50 mm, while the +0.090 mm recovery was 83% with a gangue rejection of 85%. The system displayed robust performance across all conditions investigated.

Low-grade chalcopyrite ore, heap leaching or smelting recovery route?

Chalcopyrite, the major mineral source of copper, is commonly treated pyrometallurgically, using froth flotation, smelting, converting and electrorefining processes. The ore treatment however is limited to the cut-off grade concentration below which the extraction is not economically viable. In this study a comparison of feasibility of the pyrometallurgical and hydrometallurgical treatment of low grade (0.23%–0.35% Cu), high content chalcopyrite (>90% CuFeS2) ore were studied from both technical and economic viewpoints. On a technical stance, the results of a pilot test on froth flotation of 100 t of low-grade ore are presented. The pilot test results confirm the generation of a Cu concentrate of a grade range 23.3–19.6% Cu with a copper recovery in the range 90.9–78.1%. For the hydrometallurgical treatment, bio heap leaching of 40,000 t of low-grade ore using agglomeration and aeration was proven to achieve a copper recovery of 32.6% for the chalcopyrite portion of the ore over 326 days of operation.On the economic side, the operating cost of the process per tonne of copper cathode for both processes were reported. The operating cost for the pyrometallurgical (PM) processing plant was calculated to be 1.4 times less than the hydrometallurgical (HM) processing plant. The sales revenue of the PM route was also higher than that of the HM route due to the byproducts credit. Capital cost estimates were made assuming that the current solvent extraction/electrowinning (SX/EW) facilities in a HM route and the current smelting and electrorefining plants in the PM route have enough free capacity to absorb the upstream outputs. Applying the copper extraction efficiencies of the pilot plants, the profitability indicators for both routes in treatment of 3000,000 t ore/year was studied. The impact of the interest rate was found significant in economic preference of the HM route over the PM route. This is due to the high capital cost of the mineral processing plant despite of the higher operating cost of the HM plant. The capital cost of the mineral processing plant can make the HM route feasible at interest rates higher than 27.5%. At discount rates lower than 27.5%, the PM route process is viable over the HM route at copper market price of US$9500/t. A drop in copper selling price to US$6000/t acts in favor of the HM route, making it feasible at interest rates higher than 22.4%. For a general scenario where the construction of SX/EW and smelter/refinery plants are required, the discount rate at which the net present value (NPV) of the two routes are equal has decreased from 27.5% to 17%. In this scenario, for discount rates higher than 17%, the HM route with 31% total copper recovery is more feasible than the PM route with 79% recovery.

A Sustainable Bioleaching of a Low-Grade Chalcopyrite Ore

This paper reports on a study of column bioleaching of a low-grade chalcopyrite ore that is currently dump-leached under natural biological conditions without any control over microbial populations. The experimental methodology was focused on the effect of managing the bacterial populations in a raffinate solution sourced from a dump-leach operation. This study presents results from columns of two heights (0.45 and 1.0 m). We demonstrated that intermittent irrigation enhanced the chalcopyrite dissolution during column leaching, but excessively long rest periods negatively affected the chemical and bacterial activity due to the shortage of oxidizing agents and/or nutrients for microorganisms. The recovery of low-grade chalcopyrite ore was enhanced by increasing the microbial cell density. The addition of 1.5 × 108 cells/mL to the 0.45 m column and 5.0 × 107 cells/mL to the 1 m column resulted in increased extraction, with the copper dissolution increasing from 32% to 44% in the 0.45 m column and from 30% to 40% in the 1.0 m column over 70 days of leaching. Under these conditions, the pH level remained constant at ~1.8, and the redox potential was around 840 mV vs. the SHE throughout the experiment. These results provided useful insights for evaluating a sustainable controlled dump-based technology for mineral bioprocessing.

Bioleaching of copper from chalcopyrite ore at higher NaCl concentrations

The formation of hydrolyzed ferric iron (Fe (III)) as jarosite could limit the bioleaching of copper and significantly lower the dissolution rate of low-grade chalcopyrite ore. Thus, to improve the rate through overcoming the hindered dissolution of chalcopyrite, this study investigated the influence of chloride addition into leaching lixiviant. As a microbial source, mixed mesophiles, moderately thermophilic, and thermophilic microorganisms were adapted to about 120 mM NaCl solution. After optimization of the ore bioleaching in 64 controlled mini-columns, the scaled tests in 2-m tall columns were conducted to study the overall leaching procedure and precipitation of the jarosite. Under normal aeration conditions (0.05 Nm3/m2/h) with hybrid irrigation (120 mM NaCl in H2SO4 solution at pH = 1.5), copper recovery reached 80% after 120 days while it was approximately 50% with limited one (0.003 Nm3/m2/h). The limited aeration column had a moderate oxidation–reduction potential (ORP) with values < 450 mV. This significant improvement in dissolution is explained by the reduced precipitation of passivating layer (mainly jarosite). These conclusions were also confirmed by the estimation of pyrite and natrojarosite with a modified ASTM D-2492 (MASTM D-2492). Moreover, to identify the microbial communities in the columns, DNA extraction and 16Sr RNA gene PCR amplification and sequencing were done.

Effect of polyvinyl pyrrolidone on chalcopyrite bioleaching with Acidithiobacillus ferrooxidans

Chalcopyrite (CuFeS2) is the most abundant copper-bearing mineral in nature. Large amounts of low-grade chalcopyrite ores cannot easily be utilized due to technical and economic limitations, which lead to an enormous waste of resources. Bioleaching is one of the most common methods to treat low-grade copper ores. However, the low leaching efficiency limits the industrial application of bioleaching chalcopyrite. In this study, polyvinyl pyrrolidone (PVP) was used to intensify the bioleaching of chalcopyrite with Acidithiobacillus ferrooxidans. The bioleaching results showed that PVP increased the bioleaching efficiency and the maximal effect was achieved by adding PVP after 6 days of experimental time. The solid leach residues were investigated using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectrometry (XPS) analyses to elucidate the role of PVP. Elemental sulfur and jarosite were detected on the chalcopyrite surface. These compounds may have formed a “passivation” layer, thereby hindering bioleaching as described in the literature. Moreover, PVP inhibited the generation of elemental sulfur and weakened the stability of the “passivation” layer. Additionally, PVP may have improved the surface hydrophilicity of chalcopyrite, which probably lead to an enhanced solid-liquid mass transfer.

Pollution Free and Sustainable Copper Production Using Greenhouse Gas CO2

The objectives of the present investigation to decrease the global pollution by utilizing the CO2 gas, in an effective way to produce the valuable metal copper, using low grade Cu ore which is termed as waste and not used for conventional Cu production. So the idea being waste and polluting waste are converted to useful products which will create employment, boost economy and reduce environment pollution. It is an innovative scheme for start-up. Carbonic acid produced by dissolving greenhouse gas CO2 was used for leaching low grade chalcopyrite ore under oxidizing condition. It is a single stage process with a single reactor where combined hydrometallurgical and electrometallurgical process occur. At anode an oxidizing condition is produced by dragging electron thereby increasing the rate of hydrometallurgical extraction producing Cu++ from CuFeS2. This generated Cu++ is simultaneously deposited at the cathode in the same reactor. The Cu produced was analysed and identified by RDR. The electrical power and energy consumption were computed. In the conventional cu extraction process from CuFeS2, sulphur come out as SO2 , the harmful polluting gas, in contrast in this process, sulphur came out as elemental sulphur and can be sold as by-product.

A Column Leaching Model of Low-Grade Chalcopyrite Ore: Mineral Preferences and Chemical Reactivity

Bioleaching models to examine copper extraction from low-grade chalcopyrite ores were set up to identify the influence of pyrite on leaching efficacy. A combination of scanning electron microscopy and geochemical analysis showed that extraction was marginally enhanced by the addition of pyrite when using a combination of Leptospirillum ferrooxidans, an iron oxidiser, Acidithiobacillus thiooxidans, a sulphur oxidising species and Acidithiobacillus ferrooxidans, an iron and sulphur oxidiser. Extensive biofilms formed on the pyrite surfaces (&gt;106 cells/mm2) but were severely limited on chalcopyrite, possessing approximately the same number of cells as quartz grains, an internal non-nutrient control “substrate” (with ca. 2 × 103 cells/mm2). The presence of dissolved copper did not inhibit the growth of this consortium. Indirect “bioleaching” of chalcopyrite appears to be limited by proton activity at the chalcopyrite surface.

Catalytic effect of ethylene thiourea on the leaching of chalcopyrite

Chalcopyrite leaching in acidic ferric sulfate media was improved by addition of ethylene thiourea (ETU) in shaking flask tests with the iron-oxidizing bacterium acidithiobacillus ferrooxidans. In bioreactor experiments, ETU was able to solubilize the chalcopyrite even after the mineral was pre-leached under non-catalytic conditions. Surface analysis of leached chalcopyrite mineral specimens by scanning electron microscopy and energy dispersive X-ray spectroscopy showed that the ETU-treated chalcopyrite exhibited significant surface corrosion. The shape of the etching pits suggested anisotropic corrosion towards certain 111 planes. Bioleaching experiments performed in columns showed that ETU can enhance the copper extraction rate from low-grade chalcopyrite ore.

Pre feasibility study in hydrometallurgical treatment of low-grade chalcopyrite ores from Sarcheshmeh copper mine

Chalcopyrite heap leaching is not yet a commercial reality, not just because of its lower recovery or slower kinetics, but rather, because of the economic impacts lower recovery and slower kinetics impose to the operating cost of the process. Considering the importance of the financial analysis on the economics of the operation, in this research, the economics of hydrometallurgical treatment of low-grade chalcopyrite deposit at Sarcheshmeh mine as a function of ore grade and extraction recovery were investigated. First, a brief history and theory of chalcopyrite ore leaching has been reviewed, showing that bio heap leaching at a possibly higher temperature with forced aeration is the only viable technique in treatment of low-grade chalcopyrite ores. In the economic feasibility study section, an operating cost estimate, capital cost estimate and economic analysis for a plant with 7000 tons per year copper cathode production capacity as a function of ore grades, acid consumption and heap leaching recoveries were investigated. Preliminary capital cost and operating cost estimates were made within two scenarios for a plant utilizing bio heap leaching, solvent extraction and electrowinning of low-grade chalcopyrite ore. The operating cost, for instance, was shown to be between US$5.99/kg to US$4.29/kg of copper cathode for extraction recoveries of 30% to 50% in a scenario where the construction of new SX and EW plants are required (Scenario 1). The operating cost was shown to reduce to US$5.36/kg to US$3.66/kg, for a similar recovery range, if the current SX and EW facility can absorb the bio heap leaching solution (Scenario 2). Using the operating cost data and the current copper selling price, the ore cut-off grade as a function of copper extraction efficiency was identified. The economic analysis showed that for an ore containing 0.28% copper, 7000 tons per year of copper cathode production requires a total investment of 38 million US dollar. The internal rate of return for such a plant was shown to vary between −2% to 27% for copper extraction efficiencies between 30% to 50% (Scenario 1). The sensitivity analysis of the similar plant showed that a copper selling price of US$5/kg, for instance, can even make the 50% copper extraction efficiency economically unacceptable for scenario 1.

Microstructure evolution of low-grade chalcopyrite ores in chloride leaching - A synchrotron-based X-ray CT approach combined with a data-constrained modelling (DCM)

The dissolution of metal sulfides, especially chalcopyrite and the development of porosity in samples of two different low-grade ores during chloride leaching have been studied by synchrotron-based micro-CT. Quantitative analysis of the changes was achieved by using a data-constrained modelling (DCM) approach. The result indicated that void spaces developed from the surface gradually into the core of a sample, which increased from 0.08% to as much as 11.1% in the Chilean ore, and from 0.05% to 0.93% in the Mongolian ore. Combining the results of DCM modelling and CsCl distribution test, no pore structure stretching into the core of the samples was found. As a result, the leaching of metal sulfide mostly happened in the out rim of both samples, where the mineral is directly exposed to the solution. For the Chilean ore, the volume fraction of metal sulfide decreased from 4.45% to 4.06% in 17 h in the sample as a whole, and from 1.23% to 1.2% in the core. For the Mongolian ore, the volume fraction of metal sulfide decreased from 0.23% to 0.21% in the same time span. This study provides clear evidence that contact of the target mineral with leaching solution is the primary premise for metal dissolution to happen. It also demonstrates that the combination of synchrotron CT and DCM is a useful approach for mineral micro-structure analysis.

Superconducting pulsating high gradient magnetic separation for fine weakly magnetic ores: Cases of kaolin and chalcopyrite

Superconduction was firstly combined into pulsating high gradient magnetic separation (PHGMS) technology to improve its separation performance for ultrafine magnetic particles. In this investigation, the superconducting PHGMS (SPHGMS) process was theoretically described and a cyclic pilot-scale SLon-CD100 superconducting PHGMS (SPHGMS) separator with magnetic induction reaching 9.0 T was briefly introduced, and then the separator was used to purify an ultrafine kaolin ore and separate a low-grade chalcopyrite ore. The separator has achieved a significantly improved removal rate for iron impurities from the kaolin ore compared with the PHGMS method, and it achieved an effective separation for the chalcopyrite ore with Cu recovery reaching higher than 90%. This SPHGMS method has provided a highly prospective technique for the purification of ultrafine non-metallic ores, and a potential approach for the sufficiently economic separation of magnetically non-ferrous ores such as chalcopyrite ore.

The acidic ferric sulfate leaching of primary copper sulfides under recycle solution conditions observed in heap leaching. Part 1. Effect of standard conditions

Understanding the dissolution of copper from chalcopyrite is important as chalcopyrite is the most abundant copper mineral in the earth's crust. The main method for extraction of copper from chalcopyrite is by flotation concentration before being smelted and electro-refined. However, this process is not suitable for the treatment of the vast reserves of low grade chalcopyrite ores, where hydrometallurgical extraction through heap leaching is a better option. While pressure or high temperature leaching with the addition of sodium chloride or HCl have been proposed to extract copper from chalcopyrite concentrates, this process is too expensive to treat low grade copper ores. Currently the research focus to develop a treatment process involves the use of bacteria to oxidise the sulfide minerals and produce sulfuric acid. Given the slow extraction rates of this process it requires decades to extract all the copper from the mineral which would mean the leach solution would therefore be recycled during the process once the copper had been removed. While previous studies have reported the effect of leach temperature, pH (acid concentration) and Eh on copper extraction, these have only considered initial leaching conditions. Studies using recycle leach solution conditions have not been undertaken, and this is the focus of the study reported here. The recycle solution conditions were based on a simulated long term solution composition. This article is part of a series of papers that has investigated the effect on copper and iron extraction from chalcopyrite which has evaluated conditions, major species and additives under recycle leach concentrations. This article examines the effect of the conditions, specifically temperature, pH, Eh and solids density. It was determined that the temperature had the most significant effect on the copper and iron extraction while the pH, Eh or solids density had no appreciable effect on the extraction of either copper or iron under the recycle leach conditions tested. While the effect of temperature on chalcopyrite dissolution is known, the activation energy, the rate of dissolution and the degree of copper extraction is lower under these high solute or recycle concentrations. Similar observations were found when studying pyrite but this study attributed the lowering of these parameters under recycle conditions to the sulfate concentration causing a diffusion layer around the mineral particles which alters or slows the response of pH, Eh or temperature on the dissolution reaction.

Creating a critical snapshot of the bioleaching sector by using patent databank analysis

This work defines the profile of the bio-hydrometallurgy sector by presenting a statistical analysis of the patent databank that covers the bioleaching field. The use of prior technology to take a snapshot helped provide a good panorama of the major players in the extractive metallurgy operation. Using an international classification code, 1226 patent families were retrieved. This code was chosen for microorganisms used in extracting nonferrous metals from ores or concentrates via wet processes. After a careful analysis that excluded (i) patent families without applicant information, (ii) those belonging to applicants with just a few families, (ii) those with indexing misconceptions, or (iv) duplicated families, only 312 patent families presented real interest and provided valuable information to facilitate a full analysis. Of the four largest companies producing patents in this area, BHP Billiton led the bioleaching of sulfide ores, followed by Beijing Nonferrous Central South University, which led the strain cultivation methods and inoculum generation, and Nippon Steel which led the wastewater treatment operations. This work also revealed that a classification of technical areas, although very important in classifying some technologies, should be used very carefully, because some mistakes were detected during indexing, and false results were sometimes retrieved while searching the patent databases. The evolution of patent production is closely related to the fluctuations in global metal prices. It is also affected by the strategic decision of a company CEO, especially when the time required to study a specific technology and develop an operation is very long, expensive, and requires specialized and committed technicians. Some challenges which remains to be overcome are: (i) bioleaching of low-grade chalcopyrite ores (ii) improving bacterial tolerance to chloride; (iii) industrial bioleaching of nickel laterites and (iv) bioleaching of rare earths.

Bioleaching of Low-Grade Chalcopyrite Ore by the Thermophilic Archaean &lt;i&gt;Acidianus brierleyi&lt;/i&gt;

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.

Attachment of &lt;i&gt;Acidithiobacillus&lt;/i&gt; &lt;i&gt;ferrooxidans&lt;/i&gt; and Bioleaching of Chalcopyrite under Influence of Organic Substances Associated with Copper Solvent Extraction

Small quantities of organic substances are inevitably entrained and dissolve in the aqueous raffinate during a copper solvent extraction (SX) operation. These organic substances contaminate the bioleaching environment through the loopback of the raffinate. The attachment of cells of Acidithiobacillus ferrooxidans (At. ferrooxidans) to the low grade chalcopyrite ores and the bioleaching of the ores under the influence of solvent extraction organic substances were investigated. The results showed that the cells of At. ferrooxidans were apt to attach on the SX organics-contaminated chalcopyrite ores with an adsorption ratio of about 83%, larger than that of 44% on the uncontaminated ores as a control. However, the bioleaching efficiency decreased from 25% to 15% under the influence of the SX organic substances. Obviously, an improvement of the cells attachment did not improve the bioleaching efficiency of the low grade chalcopyrite ores by At. ferrooxidans in the present of the SX organic substances. The SX organic substances impacted the metabolism of At.ferrooxidans and their bioleaching ability.

Modelling microbial transport in simulated low-grade heap bioleaching systems: The hydrodynamic dispersion model

The hydrodynamic model was developed to describe microbial growth kinetics within heap bioleaching systems. Microbial partitioning between the bulk flowing pregnant leach solution (PLS) and ore-associated phases that exist within the low-grade chalcopyrite ore bed, as a function of microbial transport between these identified phases, was investigated. Microbial transport between the bulk flowing PLS and ore-associated phases was postulated to be driven by the microbial concentration gradient between the phases, with advection and dispersion forces facilitating microbial colonisation of, and transport through, the ore bed. The population balance model (PBM) was incorporated into the hydrodynamic model to estimate mineral dissolution rates as a function of available surface area appropriately. Temporal and spatial variations in microbial concentration in the PLS and ore-associated phases are presented together with model predictions for overall ferrous and ferric iron concentrations, which account for iron concentrations in the bulk flowing PLS and that in the vicinity of the mineral surface. The model predictions for PLS and ore-associated microbial concentrations are validated with experimental data, demonstrating the improvement of this model over the previously presented ‘biomass model’. Based on Michaelis-Menten type kinetics, model-predicted true maximum specific growth rates for Acidithiobacillus ferrooxidans in the PLS and ore-associated phases were found to be 0.0004 and 0.019h−1, respectively. Estimated microbial attachment and detachment rates suggest that microbial growth is more prolific in the ore-associated phases with subsequent transport to the bulk flowing PLS. Sensitivity analysis of the hydrodynamic transport model to changes in the advection mass transfer coefficient, dispersion coefficient and inoculum size are discussed. For the current reactor configuration, increasing the irrigation rate from 2 to 2.5Lm−2h−1, i.e. increasing the advection mass transfer rate, resulted in a significant decrease in microbial retention within the ore bed.

Optimization of staged bioleaching of low-grade chalcopyrite ore in the presence and absence of chloride in the irrigating lixiviant: ANFIS simulation.

In this investigation, copper was bioleached from a low-grade chalcopyrite ore using a chloride-containing lixiviant. In this regard, firstly, the composition of the bacterial culture media was designed to control the cost in commercial application. The bacterial culture used in this process was acclimated to the presence of chloride in the lixiviant. Practically speaking, the modified culture helped the bio-heap-leaching system operate in the chloridic media. Compared to the copper recovery from the low-grade chalcopyrite by bioleaching in the absence of chloride, bioleaching in the presence of chloride resulted in improved copper recovery. The composition of the lixiviant used in this study was a modification with respect to the basal salts in 9K medium to optimize the leaching process. When leaching the ore in columns, 76.81% Cu (based on solid residues of bioleaching operation) was recovered by staged leaching with lixiviant containing 34.22mM NaCl. The quantitative findings were supported by SEM/EDS observations, X-ray elemental mapping, and mineralogical analysis of the ore before and after leaching. Finally, Adaptive neuro-fuzzy inference system (ANFIS) was used to simulate the operational parameters affecting the bioleaching operation in chloride-sulfate system.

Electrochemical study of chalcopyrite dissolution in sulfuric, nitric and hydrochloric acid solutions

Electrochemical and surface analyses were carried out to study the leaching of chalcopyrite in acid media, aiming to increase copper extraction from low-grade chalcopyrite ores. Unpublished results include the use of electrochemical impedance spectroscopy (EIS) to characterize the dissolution resistance of chalcopyrite surfaces in 0.1mol·L−1 of hydrochloric, nitric or sulfuric acids. Potentiodynamic polarization, atomic absorption spectrometry and EIS analysis showed that hydrochloric acid solutions are more efficient leaching agents than nitric and sulfuric acids. The impedance results suggested that the chalcopyrite dissolution is a diffusion-controlled process in hydrochloric and sulfuric acids. The use of Raman spectroscopy and scanning electron microscopy with energy dispersive spectrometers (SEM/EDS) allowed the partial identification of lead and bismuth sulfides as impurities. Two products were identified on the surface of chalcopyrite after anodic polarization, i.e., sulfur in the sulfuric acid only and covellite in all three acids.