Sulfide Leaching Research Articles

The Gypsum Influence on the Formation of Secondary Phases During Autoclave Leaching of Gold-Bearing Concentrates and the Silver Recovery Using Cyanidation

Autoclave leaching of sulfide concentrates may produce various ferric secondary phases, depending on the arsenic content and temperature. Silver is converted to argentojarosite, from which it is not recoverable by standard cyanidation methods. To increase silver recovery, it is necessary to reduce the argentojarosite formation during autoclave leaching. This study was devoted to the influence of gypsum on the formation of secondary phases of ferric arsenate and the subsequent recovery of gold and silver by cyanidation. The addition of gypsum at a consumption of 0.1 g/g(concentrate) helped to increase silver extraction from 13.4 to 98% at cyanidation. Gold recovery was 99%. An increase in gypsum consumption contributed to the ferric arsenate sulfate formation with an increased sulfate sulfur content, and a decrease in the As/S(sulfate) molar ratio in the cake from 3.7 to 0.88 contributed to an increase in silver extraction at cyanidation of up to 98%. Basic ferric sulfate is not formed in this case, since according to EDS mapping, the distribution of arsenic and sulfur over ferric-containing particles is uniform. According to TCLP, stable, sparingly soluble ferric arsenate phases are formed and the cake obtained after cyanidation is stable and suitable for disposal, since the final arsenic concentration in the solution was 0.45 mg/dm3.

Investigation of the high temperature leaching of a zinc sulphide concentrate in sulphuric acid solutions

Investigation of the high temperature leaching of a zinc sulphide concentrate in sulphuric acid solutions

Sulfur and metal mobilization during the life cycle of an oceanic core complex: Implications for seafloor massive sulfide deposits formation at slow and ultra-slow spreading ridges

Seafloor massive sulfide (SMS) deposits at slow and ultra-slow spreading ridges are often spatially related to, or hosted in oceanic core complexes (OCCs). The specific oceanic crust architecture, magmatism, hydrothermal fluid circulation and lithologies at OCCs, however, imply different S and metal (e.g. Cu, Zn, Co, Ni) fluxes relative to well-structured oceanic crust at-fast spreading ridges and which are not yet fully constrained. The study of S and metal distribution in the ODP Hole 735B deep drill core from the Atlantis bank allows to understand these fluxes along detachment faults and to better constrain the source zone of S and metals for OCC-related SMS deposits. Significant depletion of S, Cu, Zn and Ni are observed within the upper 250 m of the drill core where intense deformation and hydrothermal fluid circulation occurred. During the complex tectono-magmatic-hydrothermal evolution of the Atlantis Bank, four important stages are recognized for S and metal mobilization: 1) magmatic stratification leading to a higher proportion of sulfide-rich and S, Cu, Zn and Co fertile oxide gabbros in the root zone of the Atlantis Bank detachment, 2) high temperature ductile deformation leading to magmatic sulfide reworking and onset of sulfide leaching with limited metal mobilization, 3) extensive sulfide leaching and metal mobilization during amphibolite to greenschist facies metasomatism and, 4) late stage secondary sulfide precipitation and S enrichment during low temperature fluid circulation. Mass balance calculations from the source zones of the Atlantis Bank detachment highlights that metal mobilization during hydrothermal alteration of gabbroic rocks along detachment faults can fully account for the formation of OCC-related SMS deposits at slow and ultraslow spreading ridges. The Atlantis Bank detachment system, however, is gabbroic-dominated and represent the magmatic end-member of OCCs and further work is necessary for understanding metal fluxes in ultramafic-dominated detachment systems.

Copper leaching behaviour during oxygen pressure leaching of zinc sulfide concentrate

ABSTRACT To optimise copper (Cu) leaching, this study investigated Cu behaviour during a two-stage oxygen pressure leaching process of zinc sulfide concentrate (ZnS). The results indicated that maintaining low temperature, low sulfuric acid (H2SO4) concentration, and low oxygen partial pressure during the first stage of leaching the reduction of ferric iron (Fe3+) by ZnS and the weak leaching of Cu. In the second stage, increasing the temperature, H2SO4 concentration, and oxygen partial pressure enabled efficient Cu leaching while converting iron (Fe) back to Fe3+ and returning it to the first stage. This two-stage process effectively mitigated Fe hydrolysis precipitation, resulting in a small residue yield and preventing Cu incorporation into jarosite. Cyclic validation experiments were conducted under optimum experimental conditions with a residue yield of 36.1%, the dissolution rates of Zn, Cu, and Fe impurity of 98.76%, 91.65%, and 81.05%, and the Zn, Cu, and silver (Ag) contents of leaching residue were 1.61%, 0.17%, and 0.524%, respectively. The primary phases in the leach residue included lead (Pb) sulfate, sulfur, and pyrite. This approach allowed for deep leaching of Zn and Cu as well as achieving efficient Pb and Ag enrichment.

Selective recovery of antimony from Sb-bearing copper concentrates by integration of alkaline sulphide leaching solutions and microwave-assisted heating: A new sustainable processing route

The technical feasibility of leaching antimony from an antimony-bearing copper sulphide concentrate, using alkaline sulphide solutions and microwave-assisted and non-assisted heating technology, is investigated at a laboratory scale. The leaching test examines the influence of selective leaching reagent (Na2S and NaOH) concentrations, solid/liquid ratio, and temperature. The results indicate that antimony dissolution is highly selective (e.g. only Sb and As are leached), depending on the concentrations of leaching reagents and the leaching temperature. The influence of temperature on the mineral's dissolution, in the range 25–140 °C, is analysed from a thermochemical point of view using equilibrium databases. Under the optimal conditions: leaching agent: 250 g/L Na2S, 60 g/L NaOH, 2 h, 140 °C, with microwave assisted, the leaching efficiency of Sb reached 95.7 %. The antimony content in the copper concentrate is successfully reduced from 1.1 wt% to <0.2 wt% Sb, making it suitable for copper concentrate metallurgical processing. The study demonstrates that increasing temperature and NaOH/Na2S concentrations collectively enhance leaching efficiency, with a statistical significance, reducing both leaching time and the required temperature, compared to non-microwave-assisted leaching. Furthermore, it is established that excess free hydrogen sulphide ions ensure the efficient dissolution of the main impurities associated with penalties, such as antimony and arsenic, with limited copper and iron dissolution from the copper concentrate, predominantly chalcopyrite. Finally, an integrated hydrometallurgical process flowsheet for antimony removal and recovery from a sulphide copper concentrate is proposed.

Insight into the Extractive Metallurgy of Tin from Cassiterite.

This review details both the conventional and emerging methods of extracting tin from cassiterite. The emerging methods reviewed include sulphuric acid leaching of SnO, cooling crystallization of SnO, sulphide leaching, alkaline leaching, and dry chlorination. From these methods, the conventional approach (direct reduction smelting) stands out as the sole method that is suitable for industrial application, with none of the emerging ones being promising enough to be a contender. The thermodynamics involved in the hydrometallurgical extraction of tin from the mineral are also discussed. ΔGo values calculated at 25 °C for the reduction-dissolution of SnO2 using reducing gases revealed feasibility only when carbon monoxide was used. An indication of the possible species produced during the hydrolysis of the oxide of the metal (SnO2 and SnO) as a function of pH (ranging from -2 to 14 and 0 to 14 for SnO2 and SnO, respectively) was noted and highlighted to link a Pourbaix diagram generated from literature data. This diagram suggests that the solubility of SnO2 in both strongly acidic and alkaline media is possible, but with a small dissolution window in each. The purification and recovery routes of the various processing techniques were then envisaged.

75As Nuclear Magnetic Resonance Spectroscopic Investigation of the Thioarsenate Speciation in Strongly Alkaline Sulfidic Leaching Solutions

Copper ores and concentrates thereof feature an increasingly notable content of impurities such as arsenic and other hazardous elements. As an alternative to the state-of-the-art partial roasting process, arsenic could be removed by the alkaline sulfide leaching of the copper concentrates. In order to optimize and understand the processes, knowledge of the speciation and oxidation states is essential. In addition to methods such as UV/Vis spectroscopy, chromatography and ICP/MS methods, 75As NMR spectroscopy may be useful for the differentiation and quantification of the various species. Although arsenate(V) has been characterized by 75As NMR some time ago, to our knowledge, there are no data on tetrathioarsenate(V) AsS43− and the mixed oxygen/sulfur substituted mono-, di- and trithioarsenates(V) AsOxS4−x3−, x = 3, 2, 1, respectively. Therefore, we investigated several model solutions and samples from Cu-As leaching with 75As NMR. The strongly alkaline conditions of the leaching solution proved to be very advantageous for that purpose. Both the tetrathioarsenate(V) and the mixed species AsOxS4−x3− (x = 1–3) could be characterized and provide valuable data for the quantification of the material flows in the leaching process.

Sulfuric acid leaching of a complex zinc sulfide concentrate with high copper and lead concentrations under oxygen pressure

ABSTRACT This paper presents the use of an oxygen pressure-based acid leaching process for the selective extraction of basic metals from a complex zinc ore containing high concentrations of lead (6.00%) and copper (2.47%). The effects of leaching temperature, ore particle size distribution, leaching time, liquid-to-solid ratio, and oxygen partial pressure on the leaching efficiencies of zinc and copper were investigated, and the phase transformation behaviour of lead compounds was studied. Under the optimal conditions that is, a particle size of −48/+40 μm, initial sulfuric acid concentration of 150 g/L, liquid-to-solid ratio of 6:1, leaching time of 150 min, leaching temperature of 150°C, and oxygen partial pressure of 0.8 MPa – the leaching efficiencies of zinc, copper, and iron were 98.85%, 82.69%, and 33%, respectively. The leaching residue showed that almost all of the zinc sulfide was dissolved as ZnSO4, and most of the negatively charged bivalent sulfur was converted to zero-valent element sulfur. Through the pressure leaching reaction, galena in the concentrate was converted to lead jarosite (PbFe6(SO4)4(OH)12) and elemental sulfur. The formation of lead jarosite facilitated the removal of a significant portion of iron during leaching, reducing the subsequent purification burden.

Acid and ammonia leaching of secondary copper sulfides

The study focuses on understanding the efficiency and kinetics of copper recovery from secondary sulphide ores, which are increasingly becoming a significant source of copper. An experimental investigation was undertaken to assess the leaching behaviour of secondary copper sulphides in acid and ammonia media. The test work consisted of ore sample characterisation, including physico-mechanical properties determination, chemical assay, whole rock analysis, mineralogy, and copper distributions, followed by acid consumption tests, agglomeration, and agitation leach tests. Leaching tests were conducted in a lab-scale agitated reactor using 100 g of the ore sample, 0.3 l of leach solution, а stirring rate of 420 rpm and a leach time of up to 200 hours. The effect of the reaction time and oxidant (Fe3+, NO+) concentration on the copper recovery was evaluated. The maximum copper extraction was obtained in the test performed using acid media with the addition of NO+ as an oxidant. Further, a potential hydrometallurgical process option for recovering copper from secondary sulphide sources is proposed.

Ultrasonic pretreatment for enhancing flotation separation of elemental sulfur and silver-bearing lead minerals from an oxidative pressure leaching residue of zinc sulfide

Ultrasonic pretreatment was introduced to enhance the flotation separation of elemental sulfur and silver-bearing lead minerals from an ultrafine residue produced by oxidative pressure leaching of zinc sulfide. The particle size analysis of residue shows that ultrasonic pretreatment increases the number of particles with high sulfur content in the −19 μm fraction. This resulted from the associated sulfur was effectively liberated from other minerals. The complete liberation proportions of elemental sulfur and plumbojarosite in residue are respectively increased by 20.91 % and 38.53 % after ultrasonic treatment, in terms of mineral liberation analysis (MLA). Time-of-flight secondary ion mass spectrometry (ToF-SIMS) investigation implies that the surface structure difference between elemental sulfur and silver-bearing lead minerals is expanded by ultrasonic pretreatment. As a result, the separation of sulfur and silver-bearing lead minerals is significantly improved by ultrasonic pretreatment. Under optimized conditions of ultrasonic power, ultrasonic treatment time and solid weight, pilot-scale flotation produced a concentrate that the sulfur grade and recovery of concentrate increased by 11.63 % and 9.10 %, respectively, and the lead and silver recoveries of tailings increased by 8.72 % and 9.50 %, respectively, compared with those obtained by using the flotation without pretreatment. This work may provide an important reference for effectively recycling complex secondary resources and reducing the difficulty of subsequent values extraction.

Secondary uranyl arsenates–phosphates and Sb–Bi-rich minerals of the segnitite–philipsbornite series in the oxidation zone at the Prakovce-Zimná Voda REE–U–Au quartz-vein mineralisation, Western Carpathians, Slovakia

AbstractThis work is an investigation of the assemblages of supergene minerals occurring in hydrothermal REE–U–Au quartz-vein mineralisation at the Prakovce-Zimná Voda site, Slovakia. Heterogeneous uranyl arsenates and minor phosphates of the autunite group (nováčekite, kahlerite, threadgoldite, autunite, arsenuranospathite and chistyakovaite) together with scorodite and Sb–Bi-rich philipsbornite–segnitite-series minerals formed by oxidising fluids during decomposition and leaching of primary hypogene uraninite, brannerite and base-metal sulfides and sulfosalts. A progressive change of pH from acidic to near-neutral due to the gradual consumption of sulfides resulted in the formation of late phosphuranylite, pharmacosiderite and arseniosiderite. Goethite and other Fe oxides represent the latest hydrous ferric mineral phases and were formed after most of the As was already fixed in Fe arsenates. Antimony and Bi were taken up only into philipsbornite–segnitite and suggest unusual conditions during this process. X-ray absorption spectroscopy indicates that Sb in the philipsbornite–segnitite is fully oxidised (0.1–0.4 apfu Sb5+, octahedral coordination on the G site). Pentavalent Sb together with the presence of ferric oxides and arsenates and uranyl minerals suggest oxidative conditions during weathering. This study also indicates that hydrous ferric arsenates are dominant and stable secondary minerals in a supergene environment in a quartz vein rich in Fe and As accompanied by elevated concentrations of U, Pb, Sb, Bi, S, P, Ca and Ba under oxidising conditions.

Recovery of zinc resources from secondary zinc oxide via composite ammonia leaching: Analysis of Zn leaching behavior

Recovering zinc from typical industrial solid waste secondary zinc oxide (SZO) dust, rich in zinc resources, presents a significant challenge when finding an economical and green approach. This study aimed to investigate the optimal conditions for ammonia leaching of SZO dust using hydrothermal ammonia leaching methods and to explore how impurities affect zinc resource recovery in an ammonia leaching system. The results of SZO characterization before and after leaching confirmed that zinc oxide was the primary component dissolved in the ammonia leaching system. Only a fraction of zinc sulfide, lead oxide, and ferrous oxide entered the liquid phase, while most remained in the leaching slag. The study concluded that ammonium salt acted as a “dipping aid” in the ammonia leaching process and resulted in a 93.40% Zn leaching rate under optimal leaching conditions. Additionally, the study found that while impurities inhibited the leaching of Zinc Oxide in SZO, they promoted the leaching of Zinc Sulfide. Additionally, the leachate was found to contain recoverable amounts of lead and iron. These findings offer a theoretical framework for the efficient and cost-effective recovery of resources from SZO, providing valuable guidance toward achieving this objective.

Development of a Two-Stage Hydrometallurgical Process for Gold-Antimony Concentrate Treatment from the Olimpiadinskoe Deposit.

An integrated two-stage metallurgical process has been developed to process concentrates from the Olimpiadinskoe deposit, which contain high levels of antimony and arsenic. The optimal parameters for the alkaline sulfide leaching process of the initial concentrate from the Olimpiadinskoe deposit were determined to achieve the maximum extraction of antimony at a 99% level. The recommended parameters include an L:S ratio of 4.5:1, a sodium sulfide concentration of 61 g/L, a sodium hydroxide concentration of 16.5 g/L, a duration of 3 h, and a temperature of 50 °C. A synergistic effect of co-processing alkaline sulfide leach cakes with sulfuric and nitric acids was observed. The pre-treatment step reduced the nitric acid composition by converting carbonates into gypsum and increased the arsenic extraction by 15% during subsequent nitric acid leaching. The laboratory research on the nitric acid leaching of decarbonized cake established the key parameters for the maximum iron and arsenic extraction in solution (92% and 98%, respectively), including an L:S ratio of 9:1, a nitric acid concentration of 6 mol/L, and a time of 90 min. Full polynomial equations for the iron and arsenic extraction from the decarbonized cake were derived. The model demonstrated a high relevance, as evidenced by the determination coefficients (R2) of 96.7% for iron and 93.2% for arsenic. The technology also achieved a high gold recovery rate of 95% from the two-stage alkaline sulfide and nitric acid leach cake. Furthermore, the maximum deposition of arsenic from the nitrate leach solution in the form of insoluble As2S3 was determined to be 99.9%. A basic technological flow sheet diagram for processing the flotation gold-antimony concentrate from the Olimpiadinskoe deposit was developed, including two stages: the production of metallic antimony and the gold extraction from the nitric leach cake.

Process optimization and mechanism of high-efficiency germanium extracting from zinc oxide dust containing germanium enhanced by ultrasound

Aiming at the problem of low extraction efficiency of germanium in zinc oxide dust, a process of strengthening germanium leaching by ultrasonic wave in sulfuric acid leaching process was proposed. The effects of acidity, temperature, time, liquid-solid ratio, ultrasonic power and amount of iron powder on germanium leaching were investigated by response surface method, and the ultrasonic enhanced leaching process was optimized. Based on process mineralogy analysis, and germanium phase distribution analysis, which is obtained by self-establishment step-by-step extract method, the studied zinc oxide dust contains 94.1% germanium oxide and germanate, 5.13% germanium sulfide and 0.77% insoluble germanium. The results showed sulfuric acid concentration 131 g/L(1.34 mol/L), temperature 78 °C, time 22 min, liquid-solid ratio 7.6:1, ultrasonic power 270 W, iron powder content 0.71%. The leaching efficiency of germanium is 95.19%, which is 5.79% higher than that of conventional leaching method. It was found that ultrasound can destroy the particle size, reduce the cluster structure of leached products by 13.5%, inhibit the agglomeration of particles, and promote the leaching of germanate and germanium sulphide. This study is of great significance for the production of germanium.

Characterization of Extracellular Polymeric Substances Produced by an Acidianus Species and Their Relevance to Bioleaching

Extracellular polymeric substances (EPS) produced by microorganisms play a crucial role in various bioprocesses, including bioleaching. The microbial leaching of metal sulfides requires an initial cell attachment, which is facilitated by EPS. These substances are mixtures of polysaccharides, proteins, lipids, and other compounds, and their composition and properties can vary depending on the species, growth conditions, and environmental factors. Despite the significance of iron/sulfur oxidizing species in biomining processes, the knowledge of the interfacial processes between thermoacidophilic archaeal species and mineral surfaces is limited. This study examines the cell surface characteristics and EPS produced by an Acidianus strain. The research was conducted using microscopic techniques, Zeta-potential measurements, spectrophotometric methods, Fourier transform infrared spectroscopy, and fluorescence lectin-binding analysis. The results suggest that non-soluble substrates, such as sulfur or pyrite, induce changes in cell surface structures, including the presence of cell appendages, wider cell envelopes, higher hydrophobicities, and increased EPS production, compared to cells grown with soluble substrates such as tetrathionate or ferrous iron. The EPS mainly consist of proteins and carbohydrates, including glucose, manose, N-acetylgalactosamine, and N-acetylglucosamine residues. This study contributes to a better understanding of the relationship between thermophilic archaea and mineral surfaces in biomining processes.

Разработка укрупнённого адсорбера для переработки продуктивных растворов

Productive solutions obtained after leaching of ores have a complex composition, including a variety of non-ferrous and heavy metal cations. The method of extracting nickel from productive solutions after leaching of sulfide and lateritic ores is the most important process in hydrometallurgical processing. Sorption by ion-exchange resins is an alternative to existing technologies for nickel recovery from productive solutions. The ability to selectively extract nickel and regenerate makes polymeric ion-exchange resins one of the most popular sorbents in the modern world. The polymer resin sorption process avoids wastage of reagents, costly filtration, and poor nickel selectivity compared to other metal ions associated with solvent extraction processes. In order to conduct experimental studies of sorption using Amberlite IRC 748 polymer resin, it is necessary to calculate and design an adsorber. The objectives of the study include the determination of the geometric parameters of the adsorber, the parameters of the sorption/desorption process and the development of a process flow diagram. As a result of the research, an enlarged adsorber has been designed to extract nickel from the productive solution after bacterial-chemical oxidation of cobalt-copper-nickel sulfide ore, and a process flow diagram for the process of obtaining nickel salts from the productive solution has been developed. The volume of the adsorber, its height, diameter, diameter of the inlet fitting, the height of the sorbent layer, the required resin flow rate, and the duration of the process before regeneration are determined. To ensure the continuity of the process, taking into account the duration of bacterial-chemical oxidation, periodic regeneration of the sorbent, the number of adsorbers in a common installation is taken to be two. When the adsorption stage occurs in one of the apparatuses, the stage of regeneration and drying of the polymer resin proceeds in the other. The estimated sorption capacity of Amberlite IRC 748 resin was taken as 21.6 g of nickel per 0.1 kg of adsorbent. Resin desorption has been supposed to be carried out with a 10 % sulfuric acid solution, at a flow rate of 5 l/h.

Secondary phase formation during electrokinetic in situ leaching of intact copper sulphide ore

Electrokinetic in situ leaching (EK-ISL) of copper sulphides is a novel mining technology aimed at recovering copper from orebodies without physical excavation, thereby significantly reducing the environmental footprint of the mining operation. Its viability at larger scale is, however, highly dependent on developing a comprehensive understanding of the geochemical processes occurring inside the pore space of the intact rocks during leaching. One of the critical issues affecting the efficiency of copper sulphide leaching operations is the formation of secondary layers. So far, the details of their formation have only been studied under ex situ conditions and for ground samples. Therefore, this study was aimed at a detailed characterisation of the secondary leaching products under EK-ISL induced leaching conditions and how they evolved over time. We conducted time-dependant leaching tests on intact core samples with either ferric chloride or ferric sulphate as lixiviant. SEM-EDS and laser Raman microspectroscopy showed the formation of elemental sulphur as a result of the oxidation of longer-chain polysulphides. The neo-formed phases showed to slow down copper recovery, yet did not completely halt the leaching progress. Our conceptual model of the secondary layer formation suggests that the sustained dissolution of polysulphides during EK-ISL-induced leaching under the induced geochemical conditions exposes new mineral surfaces to attack. Importantly, this creates the opportunity for secondary phase re-solubilisation and therefore enhanced copper recovery.

Options for Increasing the Rate of Bioleaching of Arsenic Containing Copper Concentrate

In the present work the effect of alkaline sulfide leaching (ASL) on the extraction of copper and zinc from low-grade copper concentrate containing chalcopyrite, tennantite, sphalerite, and pyrite during batch and continuous bioleaching experiments was studied. It was demonstrated that ASL and further bioleaching may be a promising approach for treatment of copper–zinc concentrates containing tennantite as this approach allows increasing copper extraction degree in comparison to one-stage bioleaching by 1.6–2.3 times. Thus, ASL was shown to be effective for pretreatment of tennantite containing concentrates to improve bioleaching for copper extraction. At the same time, ASL led to decrease in zinc extraction by 1.4–1.5 times. Therefore, the development of combined hydrometallurgical processes including ASL and bioleaching for effective metal leaching requires further studies to avoid negative effect on zinc extraction.

Enhancing the leaching performance of molybdenite and Co-white alloy simultaneously: A structure conversion process

Molybdenite (MoS2), driven by its unique sandwich structure, is chemical inert and hydrophobic leading to a high refractory sulfide ore, and Co-white alloy, due to its grinding and corrosion resistance, is a refractory product (mainly containing Co, Fe, Cu and Si) for use in traditional hydro-metallurgical processing. In this work, a novel, two-step process was proposed to enhance the leaching performance of both molybdenite and Co-white alloy. First, prior to leaching and based on the sulfur affinity of Co, Fe and Cu, molybdenite and Co-white alloy were converted into ternary sulphides (MxMo6S8) with high leaching activity. Second, a leaching process was carried out in an autoclave with oxygen as the oxidant. Compared to molybdenite and Co-white alloy, the leaching performance of the ternary sulfides was greatly improved under moderate conditions. During the leaching of ternary sulfides, the sulfur is partially converted to elemental sulfur, which is unlike the acid leaching process of molybdenite where sulfur is oxidized to sulfuric acid. Factors affecting the decomposition of ternary sulfide were also studied in detail under moderate conditions. The optimal leaching conditions were found to be a temperature of 120 °C, a sulfuric acid concentration of 1 mol/L, a duration of 150 min, and an oxygen partial pressure of 0.95 MPa. The oxidation efficiency of molybdenum reached 99%, the elemental sulfur yield was 55%, and the leaching efficiencies of cobalt and copper were both greater than 99%.

Sulfide leaching of high-grade arsenic copper concentrates

Such factors as lower-grade copper ores, more demanding mining and technical conditions, and higher implementation costs for new development projects are typical for the Ural region in general and for the Uchalinsky Mining and Processing Plant (Uchalinsky GOK), developing tennantite-containing copper-sulfide ore reserves, in particular. Depending on the process flow design and the mineral composition of the ore, 10&ndash;70 % of arsenic is transferred into copper concentrates. The mass fraction of arsenic in the resulting copper concentrates may reach 2 %, significantly reducing the concentrate grade. Sulfide-alkaline leaching has been studied as a promising conditioning method for flotation copper concentrate. It ensures more effective arsenic removal and compliance of the final product with the requirements for further pyrometallurgical processing. The studies were carried out using a low-grade high-arsenic concentrate sample from the Uchalinsky GOK containing 16.04 wt. % Cu, 5.30 wt. % Zn, 1.36 wt. % As, and 0.19 wt. % S. It has been established that iron is predominantly occurring in the form of pyrite, with chalcopyrite and sphalerite unevenly distributed in its mass. The concentrate had high concentrations of fahlore minerals (tennantite, etc.). Studies were conducted to assess the effects of changes in the sulfide leaching process parameters (temperature, raw material size, NaOH and Na2S concentrations, solid-liquid ratio, duration) on the transfer of arsenic into the alkaline solution. The specific conditions have been established (t = 95 &deg;C; Cm(NaOH) = 3.5 M, Cm(Na2S) = 1.5 M; solidliquid ratio = 5; duration of three hours or more) that ensure almost complete removal of arsenic from the flotation concentrate to obtain a conditioned copper product meeting the requirements of GOST R 52998-2008.