Papers by Keyword: Chalcopyrite

Abstract: In this study, two black shale copper ores from different Mid-European Kupferschiefer-type deposits and their flotation concentrates were used for bioleaching tests. All samples were subjected to stirred tank bioleaching using an acidophilic, moderately thermophilic microbial consortium. The distribution of sulfides and gangue minerals in the ores, copper concentrates and residues of both, bioleaching and sterile chemical control tests were investigated using EDX-based particle analysis. The black shale ores and the extracted copper concentrates varied in their mineralogical composition with respect to the distribution of sulfides and gangue. While the copper-bearing sulfides in the Sangerhausen black shale and concentrate were dominated by bornite and chalcopyrite, the Rudna black shale and its flotation concentrate were rich in chalcocite and bornite. Differences in the portion of gangue minerals were detected in particular for carbonates that represented the dominant mineral group in the Rudna black shale and its copper concentrate. Distinct Cu dissolution kinetics and recovery rates of Co and other associated metals were observed for the various materials processed by bioleaching. Copper sulfides were completely dissolved also in both black shale ores. However, the sulfide distribution in the bioleaching residues of the Sangerhausen concentrate revealed that a significant portion of chalcopyrite was not leached. Even higher recovery rates for copper and other metals were determined for the bioleaching tests on the Rudna concentrate, in which copper sulfides were nearly completely dissolved. Alteration of copper sulfides and the formation of calcium sulfate were in particular observed in the sterile control residue of the Rudna concentrate, due to excessively use of sulfuric acid for pH stabilization. Lead sulfate precipitates increasingly occurred in the bioleaching residues, but represented also a common secondary phase in the sterile leaching residues.

Abstract: The bioleaching behaviors of chalcopyrite with two different metallogenic types by iron- and sulfur-oxidizing Sulfobacillus thermosulfidooxidans were investigated. It was found that the skarn-type chalcopyrite (STC) exhibited much faster leaching rate and the copper extraction was 33.34% after 21 days of biooxidation, while that of the porphyry-type chalcopyrite (PTC) was only 23.53%. The reasons were explained from the perspective of mineralogy. The analysis of XRD indicated that STC had slightly larger cell parameters than PTC. More stepped and bulgy structures were observed on the STC surface, as displayed in SEM images. The XPS spectra showed that copper on the surfaces of the two types of chalcopyrite mainly existed in the form of Cu(I), and STC had much higher copper content and lower Cu 2p3/2 binding energy than PTC. These differences in mineralogy resulted in the more excellent bioleaching kinetics of STC. This study is pretty useful in understanding the relation between the bioleaching behaviors of chalcopyrite and the mineralogical properties.

Abstract: Copper indium gallium selenide/sulfide (CIGS) and copper zinc tin selenide/sulfide (CZTS) are two thin film photovoltaic materials with many similar properties. Therefore, three new processing steps – which are well-known to be beneficial for CIGS solar cell processing – are developed, optimized and implemented in CZTS solar cells. For all these novel processing steps an increase in minority carrier lifetime and cell conversion efficiency is measured, as compared to standard CZTS processing. The scientific explanation of these effects is very similar to its CIGS equivalent: the incorporation of alkali metals, ammonium sulfide surface cleaning, and Al₂O₃ surface passivation leads to electrical enhancement of the CZTS bulk, front surface and reduced front interface recombination, respectively.

Abstract: The tank bioleaching of metal sulphides is an established technology. Commercial success started with the treatment of refractory gold concentrates using mesophilic micro-organisms, followed by the development of tank bioleaching processes for the treatment of base metal concentrates. This was initially a mesophilic process treating secondary copper sulphides, pentlandite and cobaltiferous pyrite. There was though limited potential for recovery of copper from chalcopyrite concentrates due to low copper extractions. Over the past decades the optimization of bioleaching processes for the treatment of chalcopyrite ores and concentrates has been the subject of numerous research programmes. The use of bioleaching for the treatment of pure chalcopyrite concentrates has, however, not found commercial application mainly due to competitive smelter prices. With this in mind, Mintek’s base metal bioleaching development over the past few years focused on the treatment of complex polymetallic concentrates containing contaminants such as As, Bi, Pb and Sb as a niche application for tank bioleaching processes. These contaminants pose problems when processed via the smelting route. This paper reviews Mintek’s involvement in the development of base metal tank bioleaching processes for the treatment of chalcopyrite and polymetallic concentrates. Examples of laboratory-scale test work as well as larger scale demonstration and commercialization of the technology are highlighted.

Abstract: Chalcopyrite (CuFeS₂) and marmatite [(Zn, Fe) S] are associated together most of the time in the raw ores and flotation concentrates. In this work, the interactions between chalcopyrite and marmatite during bioleaching by moderately thermophilic bacteria were investigated by electrochemical measurements and bioleaching experiments. In the initial stage of bioleaching of mixture of chalcopyrite and marmatite, the dissolution of marmatite was preferential, and was significantly accelerated with the addition of chalcopyrite because of the galvanic effect and catalytic effect of Cu²⁺ ions, while the dissolution of chalcopyrite was inhibited mainly due to the galvanic effect before the accomplishment of marmatite dissolution. Chalcopyrite dissolves fast when the dissolution of marmatite is finished, and small amount of marmatite cannot inhibit the final copper extraction of chalcopyrite if leaching time was long enough. Therefore, stepwise or selective bioleaching was feasible in processing mixture of chalcopyrite and marmatite to avoid complex flotation process in separating chalcopyrite and marmatite.

Abstract: This European Union ERASysApp funded study will investigate one of the major drawbacks of bioleaching of the copper containing mineral chalcopyrite, namely the long lag phase between construction and inoculation of bioleaching heaps and the release of dissolved metals. In practice, this lag phase can be up to three years and the long time period adds to the operating expenses of bioheaps for chalcopyrite dissolution. One of the major time determining factors in bioleaching heaps is suggested to be the speed of mineral colonization by the acidophilic microorganisms present. By applying confocal microscopy, metatranscriptomics, metaproteomics, bioinformatics, and computer modeling the authors aim to investigate the processes leading up to, and influencing the attachment of three moderately thermophilic sulfur-and/or iron-oxidizing model species: Acidithiobacillus caldus, Leptospirillum ferriphilum, and Sulfobacillus thermosulfidooxidans. Stirred tank reactors containing chalcopyrite concentrate will be inoculated with these species in various orders and proportions and the effects on the lag phase and rates of metal release will be compared. Meanwhile, confocal microscopy studies of cell attachment to chalcopyrite mineral particles, as well as metatranscriptomics and metaproteomics of the formed biofilms will further increase understanding of the attachment process and help develop a model thereof. By fulfilling our goal to decrease the length of the lag phase of chalcopyrite bioleaching heaps we hope to increase their economic feasibility and therefore, industrial interest in bioleaching as a sustainable technology.

Abstract: In a process of bioleaching of sulfides, the surface of target mineral is sometimes covered with intermediates and final products to interfere the extraction of metal. Understanding characterization and formation order of secondary minerals, which are responsible for passivation, is a key to resolve the passivation. In the present article, identification of secondary minerals and intermediates in a process of bioleaching of several sulfides by X-ray photoelectron spectroscopy, Raman spectroscopy, identification of jarosite group minerals using Raman spectroscopy, and expectation of formation order of secondary minerals by SEM-EDX and TEM observation are overviewed. Direct observation of a nanodomain by TEM provided a useful information on amorphous secondary minerals. In bioleaching of arsenic-bearing copper sulfides, which are expected to be a new target in the near future, a passivation model was proposed to keep maximizing Cu recovery and minimizing As solubilization, based on combination of solid characterization with aqueous observation.

Abstract: Bioleaching and biooxidation of sulfidic ores and concentrates generate very high acidities and a great of heat, which rise the temperature in the reactors or heaps, and accumulate the sulfur on the surface of the ores. Extremely thermoacidophilic archaea, mainly from the genus of Acidianus, Sulfolobus, Metallosphaera and sulfurisphaera, have great potential to contribute to biomining processes for their inherent tolerance for low pH, high temperature, and high-soluble metal concentrations. Species of the genus Metallosphaera typically grow by aerobic respiration on CO₂ with S⁰, tetrathionate (S₄O₆²⁺), and Fe²⁺ as electron donors, particularly suitble for metal extraction under high temperature by their iron- and sulfur-oxidation ability. Several species from Metallosphaera and Acidianus genera were investigated for their ability and conditions to dissolve various ores under a range of conditions. All of them showed good performance in copper extraction from chalcopyrite, with strain M.cuprina Ar-4 displaying higher activity than others. Surface analysis of chalcopyrite leached with the strain showed the leaching products accumulated on the ores. Our study will cover new understandings on the application of these thermoacidophilic archaea in biomining.

Abstract: Currently the vast majority of the world’s copper is obtained through sulfide mineral processing. Among the copper sulfides, chalcopyrite is the most economically relevant due to its abundance. Therefore, several technologies have been developed in order to achieve an efficient copper extraction from copper sulfides. Among these developments, the hydrometallurgical options of bioleaching as well as chemical chloride leaching are prevailing for secondary copper sulfides due to their good results at lab, pilot and industrial scale. Examples such as the Bacterial Thin-Layer technology developed by Minera Pudahuel in the ́80s (CL Patent 32025), as well as the Cuprochlor® process developed by Minera Michilla (CL Patent 45163), coming to the more recent “Heap leaching method” (US Patent WO2014030048A1) and the mixed version of the “Chloride method for bioleaching” patented by BHP Billiton (US Patent WO2012001501A1), are some examples that are currently being extended to the efficient copper extraction from chalcopyrite. In this work, we have compared at lab-scale BioSigma’s bioleaching technology and the industrial state-of-art chloride leaching for a mainly chalcopyritic copper sulfide ore. The metallurgical and microbial results, and the economical evaluation and comparative analysis clearly show that bioleaching presents several advantages compared to chloride leaching, being the biotechnological option more cost-effective and therefore industrially applicable.

Abstract: Bioleaching involves a chemical-microbial-driven dynamic process of oxidation and dissolution, as well as precipitation and formation of surface secondary phases that change the copper sulfide exposure/occlusion profiles. This dynamic process determines the kinetics of copper sulfides bioleaching. Former studies have shown the microbiological dynamics of the leaching solutions, and most mineralogical studies have been done with pure copper sulfide species under controlled conditions. In this work we aim to unravel the link between the microbiology and the mineralogy during the bioleaching of a mainly primary copper sulfide ore through the determination of the surface microbial and mineralogical variations in time applying process conditions. The results showed that the microbial dynamics in the leaching solutions is not representative of the bioleaching process since it differs significantly from the one established at the ore surface. Moreover, a major and fast alteration of the primary copper sulfide minerals chalcopyrite (CuFeS₂) and bornite (Cu₅FeS₄) was observed, having as the major bioleaching intermediate the formation of covellite (CuS). When the ore was subjected to a mesophilic inoculation, the microbial dynamics was modified, significantly changing the mineralogical dynamics of these primary sulfides and enhancing the overall kinetics of copper recovery.