High-grade Copper Research Articles

Phase Transformation of Arsenic, Antimony and Lead in High-Grade Copper Matte Converting

The duration of the high-grade matte converting process is short, the amount of slag is small, and it is difficult for the original impurity removal operation in the low-grade matte converting process to meet the current production demand. Because the removal method for impurity elements during high-grade matte converting is unclear, the phase transformation of impurity elements during this process is investigated in this study. The results show that arsenic exists mainly in the form of FeAsO4 and As2O5, antimony in the form of Sb and Sb2O5, and lead in the form of PbS and PbO in high-grade matte. During the converting process, arsenic and antimony mainly exist in the melt in the form of oxides and gradually aggregate into large particles with increasing copper content in the melt. Lead exists in matte in the form of PbS until the end of the converting process, and PbS is not completely oxidized until the matte converted to blister copper phase. The phase transformation characteristics of copper, iron, sulfur and impurity elements in the process of high-grade matte converting were revealed. This study provides a theoretical reference for the formulation of an efficient impurity removal scheme for the converting process.

Reclamation of iron and copper from BCL slag in Botswana

High-grade copper ores have been depleted over the years, making it a challenge in the mining industry. This investigation focused on a methodology to recover iron (Fe) and copper (Cu) from a copper/nickel slag obtained from the Bamangwato Concession Limited (BCL) mine in Botswana. In this modified flotation approach, the Response Surface Methodology (RSM) was used in conjunction with the Central Composite Design (CCD) and Analysis of Variance (ANOVA) to obtain the best optimal flotation conditions for the recovery of iron and copper. Using the RSM – CCD methodology, the optimal predicted responses were illustrated by a coefficient of determination R2 = 0. 9839 for recovery for Fe and 0.9655 for recovery for Cu. The recovery of copper increased with the increasing dosage of Na2S and collector dosage, while the increase of pH, had a decrease in recovery of copper due to the decline in the stability of the froth, which led to the resistance to form stable bubbles for efficient recovery of copper. Selective flotation of copper and iron was achieved by varying the Na2S dosage to achieve maximum recovery. Under these flotation conditions of PAX (800 g/t), pH (8), −75 μm, sulfurizing agent (Na2S, 1000 g/t), flotation time of 8 min, pH regulator of NaOH and H2SO4 and Methyl Isobutyl Carbinol (MIBC) from the experimental runs merited a grade upgrade of Cu in froth concentrate from 0.581 mass% to 0.884 mass%. An enrichment ratio of 2 was realised, with the recovery of Cu being 62%, whereas Fe in the froth concentrate increased from 69.8 mass% to 71.8 mass%. The main aim was to upgrade the grade and recovery of copper and iron to enhance the recovery for copper and iron in the next experimental stage of leaching.

Distribution of Rare Elements in Distillation Processing of Polymetallic Matte

The results of studies on the distribution of rare elements among the products of distillation processing of polymetallic mattes are present in this article. Schemes of the developed technological equipment for the implementation of the extraction processes of rare elements via the vacuum distillation of mattes are presented. Technological tests were performed with a matte of lead, copper, and antimony plants at 1100–1250 °C and a pressure of up to 700 Pa. It was established that As, Cd, Bi, In, and Ge, by more than 90% in total, are extracted into condensate and dust in the distillation process of volatile components from mattes of lead production. At the same time, antimony is distributed between the distillate residue and condensate. Antimony by 90.47%, arsenic by 78.83% and cadmium by 98.72% are distributed into sulfide condensate and dust in the distillation of copper production matte. From the matte of the antimony plant, Sb and Bi (90.76% and 89.78%, respectively) are transferred into the condensate and cyclone dust. Arsenic is distributed between the liquid and vapor phases. Based on calculations, Se and Te will be mainly concentrated in the distillation residue. High-grade copper mattes obtained in processing mattes from lead and copper plants can be further used to obtain metallic copper by converting. The condensate and dust can be processed separately or with the dust of the mainline production for rare metal extraction. Antimony matte processing condensate containing more than 70% Sb can be directed to the process of crude antimony refining.

Optimization of leaching parameters for the extraction of copper from hematite-dominated copper ore using Response Surface Methodology (RSM)

The optimization of recovery of copper from Akiri hematite-dominated copper ore using hydrometallurgy was investigated in this study. The Akiri copper ore deposit hosts a high-grade copper mineral from which copper metal can be extracted. However, the ore is dominated by gangue minerals that need to be mechanically reduced for efficient copper recovery. The purpose of this study is to optimize the extraction of the metal from hematite-dominated copper ore. The experiments that were carried out in the course of this study include crushing, pulverization,mineralogical and chemical characterizations of the sample and sulpheric acid leaching. Response surface methodology was used to optimize the system parameters namely;temperature, concentration of the leachant and contact time so that an efficient method will be developed for the extraction of copper.Chalcopyrite, covellite and cuprite are the copper minerals while the gangues minerals were quartz ,mica, hematite,etc.on the characterization of the copper ore. The major oxides in the ore are hematite ,copper oxide and silica and revealed that the ore contains 4.61% copper and 65.8% iron. Effect of three independent factors like concentration ,temperature and contact time for copper extraction from the hematite-dominated copper ore was studied.Central composite design method was applied to the proposed quadratic model that connect the factors used for best copper extraction at the best process condition. The work shows that concentration of the acid was the best efficient factor for copper extraction compare to temperature and contact time. This may be as a result of high value of F-statistics for the concentration of the leachant, which effects to high level of copper extraction.Experimental and predicted values for weight loss from the copper ore were obtained as 39.10% and 39.03% at optimum conditions, respectively. The optimum conditions of 1.5M acid concentration, 90oC reaction temperature and 90minutes contact time were obtained and from which 6.64%Cu at recovery of 92.0% and 2.31%Fe was obtained without stirring. Also, the ore was subjected to leaching with stirring at 400rpm with the optimum conditions obtained to know the effect. The grade obtained was 7.84% Cu at recovery of 83.51% and iron content 5.47%. This shows that leaching without stirring is the best option against leaching with stirring to extract the copper and to reduce the iron and other gangues contents in the copper ore.The activation energies were estimated as 13.20kJ/mol and 22.67kJ/mol for liquid film diffusion and diffusion product layer respectively, the values indicate that the leaching rate is controlled by diffusion process.

Multiple mineralization events at Paleozoic Sanchakou porphyry Cu deposit, Xinjiang: New insights from geology, geochronology, fluid inclusions, and H-O-C isotopes

The Sanchakou Cu deposit is located in the eastern section of the Dananhu arc belt in Eastern Tianshan, Xinjiang, and recorded multiple magmatic-mineralization events. The porphyry-style mineralization period produced disseminated, sulfide-dominant veined, and patchy sulfides containing chalcopyrite ± bornite ± carrolite ± molybdenite (Mol-1), which was associated with magnetite ± biotite ± chlorite ± sericite alteration in a suite of quartz diorite intrusions. The overprinting mineralization period contributed to minor Cu and Mo mineralization, featured by later disseminated molybdenite (Mol-2), chalcopyrite, and widespread low-temperature (<280 °C) vein-type stellerite assemblages. Two distinct geological ages of molybdenite (including Mol-1 and Mol-2) from Sanchakou have been determined in this study. The old 187Re/187Os isochron age for euhedral Mol-1 represents the timing of original porphyry-style mineralization (386 ± 16 Ma), in agreement with LA-ICP-MS zircon U-Pb age of dark diorite dykes (390 ± 11 Ma). The young 187Re/187Os age for fine-grained Mol-2 is interpreted to be a maximum age of sulfide formation or remobilization (364 ± 15 Ma), most likely associated with the emplacement of Late Devonian gneissic granite intrusions. Fluid inclusion microthermometry, mineralogy, and physicochemical calculations for the porphyry-type mineralization period (including four stages) at Sanchakou suggest that earlier magmatic fluids have evolved from high T (310–460 °C), high logfO2 (−22 to − 26), and alkaline condition during stage I to low T, low logfO2 (−34), and acidic condition during stage II. The decrease of oxygen fugacity caused by abundant deposition of magnetite in stage I produced large-scale Cu and Mo precipitation. Stage II to IV fluids have gradually decreasing temperatures and salinities, due to involvement of meteoric water that also facilitates the ore deposition. This result is consistent with the evolution of O isotope compositions of the fluids (δ18Ofluids = − 9.3 to 4.3), further implying the significance of fluid mixing instead of fluid boiling that caused ore deposition. Locally high-grade copper concentrations at Sanchakou are likely attributed to the overprinting modification event on the original ore bodies. All of these observations indicate that the Paleozoic Sanchakou ore-forming system is similar to other deformed porphyry Cu systems in the Central Asian orogenic belt (CAOB) and worldwide. The Cu mineralization and modification event at Sanchakou is coincident with the second peak productivity in CAOB. We further suggest that the Paleozoic diorite complex and stellerite alteration can be as a significant exploration target for porphyry-style Cu mineralization in the Eastern Tianshan.

RECOVERY TEMBAGA DARI LARUTAN TEMBAGA SULFAT MELALUI METODE SEMENTASI MENGGUNAKAN BESI

This study aims to optimize the copper recovery process from copper sulfate solution using the cementation method with iron as the precipitating agent. This method offers an efficient and sustainable solution to address the challenges of copper recovery from copper sulfate solutions, which has become increasingly crucial due to the declining supply of high-grade copper ore. The variables optimized in this research encompass the optimization of stirring speed (50 RPM to 300 RPM), iron addition (0.5 to 3 times the stoichiometric reaction), temperature (30 to 70°C), and reaction time (15 to 120 minutes). The research results indicate that the optimal conditions for copper recovery are achieved at a stirring speed of 200 RPM, iron addition of 2 times the stoichiometric reaction, a temperature of 70°C, and a reaction time of 120 minutes. Under these conditions, the percentage of copper recovery from the copper sulfate solution using the cementation method reaches 99.37%, demonstrating a high level of efficiency in this approach.

A new piece of the puzzle: slag and ore analysis to reconstruct the prehispanic smelting technology at the Atacama Desert, Chile

The Incas appropriated many local metallurgical technologies throughout the Andes, each of which had its unique peculiarities and was based on local ancestral knowledge. The widespread use of tin-bronze during the Inca expansion, the development of mining and smelting sites, as well as ethno-historical records evidence the Incas’ interest in copper smelting, a key activity in the Andes since ca. 1400 BC. However, little is known about the technical parameters achieved by ancient metallurgists and the changes that occurred during the Inca expansion. In this paper, we address these changes through a case study of Copiapó valley, focusing on the Viña del Cerro site, one of the most famous Inca smelting centres of the southern Andes. Although this place was architectonically restructured by the Incas, its operations began long before the imperial expansion and used wind-powered furnaces. We analysed 19 slag and 11 copper ore samples using OM, SEM–EDS, WD-XRF, and XRD analyses. Results identified heterogeneous and viscous slags, rich in SiO2 (43 wt%) and poor in FeO (13 wt%). Copper retention was high (up to 60 wt%). Microstructural analyses indicate that slags were formed under unstable oxidising conditions, reaching temperatures that ranged between 1000 to 1100 °C. The copper produced was very pure. High-grade copper ores containing up to 69 wt% CuO were reduced at the site, combining carbonates (malachite, azurite), halides (buttgenbachite, clinoatacamite), and some sulphates (brochantite). We propose that even under the relatively unfavourable conditions for slag formation, the smelting conditions generated at Viña del Cerro were competent enough to extract metal, but not necessarily enough to form liquid slag. These conditions were facilitated by the local metallurgists’ thorough knowledge of the wind flow and their ability to select the right ore. This new information contributes to understanding the efficiency of metallurgical technology and the knowledge, skills, and adaptability of the ancient metallurgists from Copiapó valley, a group that was integrated into the economic networks of the Inca Empire.

Recovery of high-grade copper from waste polyester imide enameled wires by pyrolysis and ultrasonic treatment

Recovery of high-grade copper from waste enameled wires can effectively alleviate the shortage of copper resources. In this paper, the evolution of pyrolytic products during pyrolysis of waste polyester imide enameled wires was analyzed and the thermal decomposition mechanism was presented. A technology consisting pyrolysis and ultrasonic was proposed to achieve deep decarbonization. The results showed that the pyrolysis process was mainly divided into two stages. Below 500 °C, polyester imide was first depolymerized into large monomer, and then pyrolytic oil containing ketones, imides, amines and aromatic compounds was generated by random fracture (three main ways) and free radical reactions. With increase of temperature, the free radical reactions of small molecules to produce carbon and pyrolytic gas were dominant. The decarbonization efficiency reached 99.99% and the high-grade copper was obtained under the optimal conditions. This study provided the theoretical basis for recycling high-grade copper from waste enameled wires.

Process for Concentration of Low Grade Copper Ore – A Process Design

The paper deals with the results of characterisation and flotation studies carried out on a low grade and complex copper ore sample with a view to design process for its concentration. Flotation studies were carried out under varying conditions of process parameters. Effects of granulometry of the feed, dosage of sodium iso-propyl xanthate as collector, pH and gangue depressant/dispersant were studied. Sulphidization technique and use of potassium octyl hydroxamate as auxiliary collector for flotation of oxidised minerals were observed to enhance copper recovery. Use of sodium silicate as depressant/dispersant for siliceous gangues helped in improving grade of copper concentrate. Rougher followed by multi-stage cleaning were found necessary to produce a high grade copper concentrate. Based on the studies undertaken the process was designed for concentration of the low grade copper ore sample.

Direct-to-blister smelting of copper concentrate based on a calcium ferrite slag system

The direct-to-blister smelting process realizes single furnace smelting from chalcocite to blister copper. This process saves the matte transport process, avoids multiple feeding in the smelting process, and has the advantages of high productivity, a short production process, and less SO2 pollution. By comparing with the phase diagram of iron silicate slag system, it shows that calcium ferrite slag system is more suitable for direct-to-blister smelting under the condition of high oxygen potential. In this study, high-grade copper concentrate was used as the raw material and direct-to-blister smelting experiments were carried out at the laboratory scale. The variation of copper recovery with CaO/Fe ratio, smelting temperature and sedimentation time was studied. The phase composition of slag and the loss of copper in slag were analyzed by X-ray diffraction (XRD) and scanning electron microscopy with an energy spectrometer (SEM-EDS). The results showed that by adjusting process parameters, the copper recovery can reach 90.15 wt.% and the blister copper grade is more than 98.50 wt.%. It provides a theoretical basis for the industrial application of calcium ferrite slag in direct-to-blister smelting.

Distribution behavior and deportation of arsenic in copper top-blown smelting process

In recent years, the impurity content in copper concentrate increases gradually with the consumption of high-grade copper ore. When the arsenic content in the raw materials increases, large amounts of arsenic enter the sulfuric acid system, resulting in large amounts of waste acid that put great pressure on production and environmental protection. Using the distribution characteristics of arsenic in each phase, the possibility of enriching arsenic in the form of stable arsenates in the slag was investigated to enrich arsenic in the form of stable arsenates in the slag. It is shown that increasing CaO content in slag at relatively low temperatures, controlling the slag type and changing the slag composition effectively improved the ability of the slag to absorb arsenic. Based on a theoretical analysis used to optimize the process parameters and determine a reasonable slag type, an oxygen-enriched top-blown smelting experiment was conducted with mixed copper concentrates. The mechanism of arsenic fixation in smelting slag at a smelting temperature of 1180 °C (1453 K) was investigated, and the results showed that the As content in slag was increased by 20∼50% and decreased by 10∼30% and 10∼20% in the dust and matte, respectively. Thus, arsenic is fixed in silicate in the form of stable arsenate, which can be an effective and safe treatment solution for copper smelting processes.

High-Grade Copper and Gold Deposited During Postpotassic Chlorite-White Mica-Albite Stage in the Far Southeast Porphyry Deposit, Philippines

Abstract Ninety-eight underground diamond holes (~102 km) drilled by Far Southeast Gold Resources Inc. at the Far Southeast porphyry Cu-Au deposit, Philippines, from 2011 to mid-2013, provide a three-dimensional exposure of the deposit between 700- and –750-m elevation, with surface at ~1,400-m elevation. Far Southeast contains an inferred resource of 891.7 million tonnes (Mt) averaging 0.7 g/t Au and 0.5 wt % Cu, equivalent to 19.8 Moz Au and 4.5 Mt Cu. This contribution reports the spatial and temporal distribution of alteration and mineralization at Far Southeast, notably a white-mica–chlorite-albite assemblage that formed after early secondary biotite and before late quartz–white-mica–pyrite alteration and that is associated with the highest copper and gold grades. Alteration assemblages were determined by drill core logging, short-wavelength infrared (SWIR) spectral analysis, petrographic examination, and a quantitative evaluation of materials by scanning electron microscopy (QEMSCAN) study. Alteration is limited around sparse veins or pervasive where vein density is high and the alteration halos coalesce. The alteration and mineralization zones with increasing depth are as follows: (1) the lithocap of quartz-alunite–dominated advanced argillic-silicic alteration that hosts part of the Lepanto high-sulfidation Cu-Au epithermal deposit (mostly above ~700-m elevation), (2) an aluminosilicate-dominated zone with coexisting pyrophyllite-diaspore ± kandite ± alunite and white mica (~700- to ~100-m elevation), (3) porphyry-style assemblages characterized by stockwork veins (below ~500-m elevation), (4) the 1 wt % Cu equivalent ore shell (~400- to –300-m elevation), and (5) an underlying subeconomic zone (about –300- to –750-m elevation, the base of drilling). The ore shells have a typical bell shape centered on a dioritic intrusive complex. The paragenetic sequence of the porphyry deposit includes stage 1 granular gray to white quartz-rich (± anhydrite ± magnetite ± biotite) veins with biotite-magnetite alteration. These were cut by stage 2 lavender-colored euhedral quartz-rich (± anhydrite ± sulfides) veins, with halos of greenish white-mica–chlorite-albite alteration. The white mica is largely illite, with an average 2,203-nm Al-OH wavelength position. The albite may reflect the mafic nature of the diorite magmatism. The quartz veins of this stage are associated with the bulk of copper deposited as chalcopyrite and bornite, as well as gold. Thin Cu sulfide (chalcopyrite, minor bornite) veins with minor quartz and/or anhydrite (paint veins), with or without a white-mica halo, also occur. These veins were followed by stage 3 anhydrite-rich pyrite-quartz veins with white-mica (avg 2,197 nm, illite)–pyrite alteration halos. Combined with previous studies, we conclude that this porphyry system, including the Far Southeast porphyry and Lepanto high-sulfidation Cu-Au deposits, evolved over a period of 0.1–0.2 m.y. Three diorite porphyry stocks were emplaced, and by ~1.4 Ma biotite-magnetite–style alteration formed with quartz-anhydrite veins and deposition of ≤0.5% Cu and ≤0.5 g/t Au (stage 1); coupled with this alteration style, a barren lithocap of residual quartz with quartz-alunite halo plus kandite ± pyrophyllite and/or diaspore formed at shallower depth (&amp;gt;700-m elevation). Subsequently, lavender quartz and anhydrite veins with bornite and chalcopyrite (high-grade stage, avg ~1 wt % Cu and ~1 g/t Au) and white-mica–chlorite-albite halos formed below ~400-m elevation (stage 2). They were accompanied by local pyrite replacement, the formation of hydrothermal breccias and Cu sulfide (paint) veins. Stage 2 was followed at ~1.3 Ma by the formation of igneous breccias largely along the margins of the high-grade zones and stage 3 pyrite-quartz-anhydrite ± chalcopyrite veins with white-mica (mostly illitic) halos. At shallower depths in the transition to the base of the lithocap, cooling led to the formation of aluminosilicate minerals (mainly pyrophyllite ± diaspore ± dickite) with anhydrite plus high-sulfidation-state sulfides and pyrite veinlets. Consistent with previous studies, it is likely that the lithocap-hosted enargite-Au mineralization formed during this later period.

Bulk flotation followed by selective leaching with biogenic ferric iron is a promising solution for eco-friendly processing of complex sulfidic ores.

The development of cost-effective environmentally friendly technologies is of current importance for the intensification of metal recovery. Here, we propose a new direction in the use of a two-step process for the treatment of complex sulfidic ores. In the first step, ore flotation allows the obtainment of a bulk copper-zinc concentrate and low-toxicity waste. In the second step, zinc is selectively extracted by chemical leaching with a biogenic ferric iron solution, while copper is accumulated in the leach residue. Importantly, the efficiency of this step depends on the chemical and mineralogical composition of polymetallic concentrates. Four samples of the copper-zinc sulfide concentrate with various contents of copper and zinc have been leached in multiple cycles at 80°C, 10% of pulp density, and pH 1.3-1.5. The leaching of the concentrate that contained 14.7% of copper and 5.0% of zinc for three leaching cycles (total duration, 5.75h) allowed the obtainment of a leach residue containing 15.3 and 0.14% of copper and zinc, respectively. At the same time, the leaching of another concentrate that contained 19.2% of copper and 2.64% of zinc after one leaching cycle (total duration, 0.67h) led to copper and zinc contents of 19.1 and 0.72%, respectively, in the leach residue. Therefore, the treatment of only two concentrates allowed the obtainment of high-grade copper concentrates containing low amounts of zinc. Ferric iron, the oxidant of sulfide minerals, was fully regenerated in leachate within 30-35h at 40°C using an acidophilic microbial community dominated by Leptospirillum ferriphilum, Sulfobacillus spp., and Ferroplasma acidiphilum. The loss of copper and zinc in solid waste of the bioregeneration did not exceed 1.0% and 1.8%, respectively. The proposed flowsheet of bulk concentrate processing has several important advantages over conventional technologies, including short duration of leaching, formation of low-toxicity solid waste, and pyrometallurgical processing of only high-grade copper concentrates. This approach can be a promising solution for the efficient processing of polymetallic bulk concentrates.

Comparison of Bio- and Ferric Leaching for Beneficiation of Bulk Copper-Nickel Sulfidic Concentrate

Processing of sulfidic raw materials, including bulk concentrates of nonferrous metals, is a problem of current importance in metallurgy and waste recycling. In this study, leaching with a chemical ferric iron reagent was compared to two bio-approaches to process a bulk copper-nickel concentrate: (1) ferric leaching with a solution obtained by microbial oxidation and (2) stirred-tank bioleaching using an active acidophilic microbial community. The results of both the chemical and bio-processes indicated nickel dissolution, while copper was accumulated in leach residues. After short-term high-temperature leaching with the chemical or bio- solution (Fe3+, 10 g/L), the nickel content in solids decreased by 0.7 and 2.6%, respectively, while the copper content slightly increased (by 1.5–3.2%). Bioleaching at 40°C was characterized by a considerably higher efficacy of the process: nickel leaching reached 86.7%, and the copper content increased by ~5% in the bioleach residue. Based on these results, ferric leaching can be considered an inefficient method for selective nickel removal, while bioleaching may be a promising cost-effective approach characterized by relatively low environmental hazards to obtain a high-grade copper product. Moreover, ferric leaching with the bio-solution can improve the grade of monometallic sulfidic concentrates due to additional selective nickel extraction.

Sustainable Use of Copper Resources: Beneficiation of Low-Grade Copper Ores

The global market has announced copper as a modern energy metal and finds its extensive utilization in the construction industry, electrical wiring, power transmission lines, alloying, anticorrosive coating, heat exchangers, refrigeration tubing, etc. Copper ore is primarily beneficiated from sulphide mineral deposits. Due to high-grade copper sulphide deposit exhaustion, the focus has now shifted towards recovery from different lean-grade oxide and mixed ore deposits. The present paper summarizes the utilization of copper as a clean energy mineral and its importance in the current renewable energy sector. Extensive research has been carried out on the flotation of copper sulphide ore as compared to copper oxide and mixed type ores. Besides flotation, other beneficiation techniques (selective flocculation and gravity separation) are also discussed in the present review. A few novel pretreatment methods are currently being studied for copper ore to intensify the separation for higher productivity.

Effect of Temperature on Biobeneficiation of Bulk Copper-Nickel Concentrate with Thermoacidophilic Microbial Communities

Bioleaching of the bulk copper–nickel sulfide concentrate was proposed as a method to remove nickel from it and to obtain a concentrate containing copper as chalcopyrite. This approach is based on the different refractoriness of sulfide minerals in ferric sulfate solutions and oxidation by acidophilic microorganisms. The bulk concentrate contained 10.8% copper in the form of chalcopyrite (CuFeS2) and 7.2% nickel that occurred in pentlandite ((Ni,Fe)9S8) and violarite (FeNi2S4). Three microbial communities grown at 35, 40, and 50 °C were used for bioleaching. The microbial community at 40 °C was the most diverse in the genus and species composition. At all temperatures of the process, the key roles in bioleaching belonged to mixotrophic and heterotrophic acidophiles. The highest levels of nickel leaching of 97.2 and 96.3% were observed in the case of communities growing at 40 and 50 °C, respectively. At the same time, the bioleach residue, which could be characterized as a marketable high-grade copper (chalcopyrite) concentrate, was obtained only at 40 °C. This solid contained 15.6% copper and 0.54% nickel. Thus, the biobeneficiation of bulk sulfide concentrates can be a promising field of biohydrometallurgy.

Biobeneficiation of bulk copper-zinc and copper-nickel concentrates at different temperatures

One of the problems associated with polymetallic ore concentration is the separation of bulk concentrates, which is difficult due to the textural and structural characteristics of mineral particles. In this paper, we proposed selective bioleaching of zinc and nickel from bulk copper-zinc and copper-nickel sulfide concentrates, respectively, to extract these metals into solution and to produce high-grade copper concentrates. In the copper-zinc concentrate, zinc occurred in sphalerite (ZnS). In the copper-nickel concentrate, nickel occurred in pentlandite ((Ni,Fe)9S8) and violarite (FeNi2S4). In both concentrates, which also contained pyrite (FeS2) and pyrrhotite (Fe1-xS), copper occurred in chalcopyrite (CuFeS2). Bioleaching of the concentrates by acidophilic microbial communities at 30 and 40 °C was compared. Bioleaching at increased temperature was characterized by the higher intensity of the process. Complete removal of zinc from the copper-zinc concentrate occurred within 15 days at 30 °C and 4 days at 40 °C, while the copper content in the bioleach residue increased by 7.5 and 5.9%, respectively. Nickel leaching was less efficient: 67.6% at 30 °C and 86.7% at 40 °C after 22 days of the process. At the same time, the copper content in the bioleach residue increased by 2.7 and 5.7%. Dissolution of violarite proceeded more rapidly than that of pentlandite. More efficient zinc and nickel leaching from the concentrates at 40 °C could be associated with a higher microbial diversity in the communities formed at this temperature. An increase in the proportion of bacteria of the genera Sulfobacillus and Ferrimicrobium, as well as archaea of the families Ferroplasmaceae and Cuniculiplasmataceae, was shown. At both temperatures, Acidithiobacillus and Leptospirillum bacteria prevailed during the biooxidation of both, the copper-zinc and copper-nickel concentrates.

Recovery of high-grade copper matte by selective sulfurization of CuO–Fe2O3–SiO2–CaO system

The separation of Cu from the Cu x O-Fe x O containing waste (such as copper slag and electroplating sludge) is always intractable by using pyrometallurgy method. The carbothermic reduction methods, as well as the conventional sulfurization technology by using sulfurization agent FeS 2 , will introduce lots of iron into the prepared Cu–Fe alloy or Cu–Fe–S matte, and this results in the difficulty in further separation of Cu from Fe. In this work, CaS is utilized as the new sulfurization agent, and the iron content of prepared Cu–Fe–S matte is lower than 5%, while the copper grade is improved to about 76–79%. Such products could be used as the raw materials for producing metallic copper. According to the experimental results, at 1450 °C, the copper oxides in CuO–Fe 2 O 3 –SiO 2 –CaO system is selectively sulfurized by CaS, and Cu 2 S dominated product is formed and separated from slags. The recovery extent of copper reaches 98% when the CaS addition is 1.15 times (1.15CaS) of the stoichiometric quantity required. However, the increase of CaS addition (1.6CaS) will lead to the sulfurization of iron oxides, and make the iron content in Cu–Fe–S matte increase to 15%. Besides, when the Cu/Fe ratio (in mass) of synthetic waste is 0.5, part of the CaS is oxidized by Fe 2 O 3 , which results in the recovery extent of Cu to only about 73.30%. However, the copper recovery extent could be improved to 97% by adding extra reductant carbon.

Recovery of high-grade copper concentrate from sulfur-rich porphyry ore using tricarboxystarch micromolecule as pyrite depressant

Tricarboxystarch (sodium salt), also known as TCSS, has been studied as a selective depressant of pyrite in chalcopyrite flotation using xanthate as a collector. In microflotation, tricarboxystarch achieved strong and selective depression of pyrite flotation than chalcopyrite under weakly acidic conditions. In this study, the performance of tricarboxystarch as a pyrite depressant was further investigated by using it in batch flotation experiments on sulfur-rich copper sulfide ore. The effects of the addition of tricarboxystarch on improving Cu grade and reducing S grade were investigated at different pH of solution and different doses of reagent. The overall batch experiment consisted of bulk roughing and cleaning flotation, followed by the removal of pyrite with the addition of depressant. Using tricarboxystarch as a depressant, a new environmentally friendly closed-circuit beneficiation process for a sulfur-rich copper ore was also designed in this work. The results of batch flotation experiments show that the addition of a low dose of tricarboxystarch under weakly acidic conditions (pH 6) yields a very high grade copper concentrate containing approximately 21.85% Cu and 33.78% S. As an inexpensive and eco-friendly polymer, tricarboxystarch usage may significantly reduce the reagent cost and potential environmental impact in the mineral industry.

Fluid evolution of a hematite-dominated, magmatic-hydrothermal Cu-Au deposit at Qibaoshan, Shandong Province, China

Qibaoshan is a magmatic-hydrothermal, polymetallic ore deposit located to the northwest of Wulian district, Shandong Province, China. The deposit hosts high grade copper and gold, which are the primary targets of currently active open-pit mining. However, the type, origin and mineralization mechanism(s) at Qibaoshan are still debated. Here, we studied the mineral assemblages, hydrothermal alteration, paragenesis of mineralization, and fluid evolution of the Qibaoshan deposit. Qibaoshan shares many similarities with some iron oxide-copper–gold (IOCG) deposits such as Mantoverde (Chile). The ore bodies of the Qibaoshan deposit are hosted in and structurally controlled by breccias, and are composed almost invariably of chlorite, coarse specular hematite, quartz and carbonates with subordinate pyrite and chalcopyrite. Passing inwards from the deep and peripheral parts towards the central ore zones, the intermediate- to felsic-host rocks mainly follow a sequence of hydrothermal alteration consisting of pervasive potassic and later acid alteration (chloritic and sericitic) events. The acid alteration is associated with the first pulse of copper deposition; which is followed by the deposition of specular hematite + euhedral quartz; then the deposition of (2nd) chalcopyrite + pyrite; and finally, late calcite + siderite precipitation in the vein centerlines. Each successive stage of this vein paragenesis shows clear evidence of precipitation into open space.The fluid evolution at Qibaoshan shows a transition from early, highly saline (47 wt% NaCleq), high temperature (396 °C), and low pressure fluids during the acid alteration; towards a moderate salinity (26 wt% NaCleq), intermediate temperature (272 °C) and pressure fluid during hematite growth; and then towards a low salinity (11 wt% NaCleq), low temperature (77 °C) fluid during the precipitation of euhedral quartz. The initial, high temperature stage showed features indicative of magmatic-hydrothermal origin. This first sequence included a metal-bearing (iron > copper) fluid pulse. Over the course of this sequence, the fluids showed gradual cooling coupled with a gradual decrease in salinity, probably indicating dilution as the early magmatic fluids mixed with externally derived meteoric water. After that, another metal-bearing (copper > iron) fluid pulse resulted in abundant (2nd) copper deposition in the veins. This vein sulfide stage was then followed by a trend towards lower salinity (14 wt% NaCleq), moderate temperature (225 °C) fluids that drove the precipitation of late carbonates. Overall, these results suggest that Qibaoshan is a magmatic-hydrothermal, IOCG-like deposit, with at least two magmatic fluid pulses, each followed by subsequent cooling and dilution by mixing with meteoric water that was tied strongly to the ore deposition.