Chalcopyrite Surface Research Articles

The effects of hydroxyl on selective separation of chalcopyrite from pyrite: A mechanism study

The separation of chalcopyrite from pyrite is usually carried out under high alkaline conditions. However, the separation mechanism of chalcopyrite from pyrite under high alkaline conditions was still unclear. In this work, the effects of hydroxyl on the separation of chalcopyrite from pyrite were systematically investigated by flotation tests, Zeta potential measurements, adsorption studies, Fourier Transform Infrared Spectrometer (FTIR) analysis and density functional theory (DFT) calculations. Micro-flotation results showed that chalcopyrite could be separated from pyrite in high alkaline pulp. Furthermore, Zeta potential indicated that the adsorption of xanthate on the surface of pyrite was obviously weakened at pH = 12, while its on chalcopyrite surface had little change. Such results were confirmed by adsorption tests. The adsorption amount of sodium butyl xanthate (SBX) on chalcopyrite was much higher than pyrite at pH = 12. Besides, FTIR analysis demonstrated that the characteristic peaks (C=S, C–O–C) of SBX were observed for chalcopyrite, while no characteristic peak of SBX was found for pyrite. DFT calculation further confirmed that the competitiveness of xanthate on the surface Cu sites of chalcopyrite was stronger than on the surface Fe sites of pyrite. Hydroxyl ion can be effectively adsorbed on pyrite rather than chalcopyrite, owing to its stronger affinity with pyrite.

Enhanced flotation of chalcopyrite particles by grinding with short cylinder media

In mineral processing, sufficiently liberated target minerals by grinding is a prerequisite for successful flotation. Rod grinding produces particles with a narrower size range and better floatability through line contacts, but with a lower production capacity compared to balls (point contacts). As a result, balls remain as the preferred media for most dressing plants. However, balls produce many ultra-coarse and ultra-fine particles. Hence, grinding media with multiple contact forms could offer a compromise, which can combine the advantages of both rods and balls. In this paper, the performance of short cylinders which comminute minerals in point and line contact modes and ball grinding media were compared and evaluated using chalcopyrite as a test mineral. The grinding results show that short cylinders generate more angular particles with intermediate particle sizes and have a higher grinding efficiency compared with balls. Short cylinders selectively produce more active {112} surfaces of chalcopyrite, which possess higher adsorption capacity with collectors and were preferentially floated as the concentrate. Flotation tests confirm that the real ore particles ground by short cylinders have higher liberation degree and exhibit a higher flotation recovery of chalcopyrite than ore ground using balls. This study provides a reference scheme for the grinding and flotation optimization of valuable minerals.

Adsorption of a new reagent scheme on chalcopyrite and molybdenite surfaces causing an efficiency flotation separation: Insights from first-principles calculations

Herein, a new and environmentally friendly process scheme containing PGA as depressant and Z200 as collector for chalcopyrite-molybdenite bulk flotation and STG as depressant for chalcopyrite/molybdenite separation flotation was applied to the separation of pyritic Cu-Mo sulfide ore from Daye, Hubei Province, China. The flotation results showed that the new process scheme not only can efficiently achieve the flotation separation of chalcopyrite and molybdenite, but also can reduce the dosage of STG in chalcopyrite/molybdenite separation compared with the traditional process combining CaO and BX. The closed-circuit flotation experiment results further demonstrated this preferable result. Besides, the differences in the adsorption of STG on the chalcopyrite (112) surface in the presence of Z200 and BX were investigated by first-principles calculations at the atomic level. The calculation results showed that the STG adsorption on chalcopyrite (112) surface in the presence of Z200 was easier than that in the presence of BX, and the STG adsorption weakened the Z200 adsorption on chalcopyrite (112) surface, which provides atomic-scale explanations to the less STG dosage in chalcopyrite/molybdenite separation. This new reagent scheme has environmental advantages and great reference value for the separation of other pyritic copper-molybdenum sulfide ores.

Selective Ozone-Assisted Acid Leaching of Copper from Copper Smelter Slag by Using Isopropanol as a Solvent

Copper content in copper smelter slag exceeds that in copper ores, which has attracted increasing interest to recover copper from this by-product of pyrometallurgical copper production. The isopropanol-sulfuric acid-ozone system has been tested under different conditions to extract this metal from copper smelter slag containing chalcopyrite as a copper mineral. Isopropanol as a solvent played a key role in increasing the copper recovery to 87% after 5 h of leaching, while the use of an aqueous solution of sulfuric acid allowed only 13% of copper to be recovered. Iron extraction under these conditions was only 10%. The role of ozone was spectroscopically proven to oxidize ferrous ions to form ferric ions, which are effective oxidizers of chalcopyrite. The presence of copper in solution in the form of cuprous (Cu+) ions was proven electrochemically. The increased copper extraction in the solution was caused by the stabilization of cuprous ions by isopropanol. The limiting stage of the process was the chemical reaction on the chalcopyrite surface with the activation energy of 73.4 kJ mol−1.

A DFT study of the adsorption of O2 and [Fe(H2O)2(OH)3] on the (001) and (112) surfaces of chalcopyrite.

The oxidation of chalcopyrite, CuFeS2, is still not well understood and relevant in the context of the hydrometallurgical extraction of copper. Herein, we used DFT calculations within the periodic boundary conditions formalism to study the adsorption of O2 and [Fe(H2O)2(OH)3] molecules on the (001) and (112) surfaces of CuFeS2. The O2 molecule adsorbs strongly by a dissociative pathway at sulfur atoms on the (001) surface with an adsorption energy of - 76.5kcalmol-1. The surface is chemically modified forming SO2 groups, in which the S-O bond length is calculated to be 1.47 and 1.54Å. PDOS and Löwdin charges analyses indicate the oxidation of the sulfur atoms on the surface. We tested different adsorption modes of [Fe(H2O)2(OH)3], and a bidantade coordination with the Oads-Fesur and Feads-Ssur bond lengths of 2.02 and 2.47Å is the most favorable with an adsorption energy of - 18.8kcalmol-1 on the (001) surface. Adsorptions of each species are also observed on the (112) surface, but they are weaker than those observed on the (001) surface.

AFM Image Analysis of the Adsorption of Xanthate and Dialkyl Dithiophosphate on Chalcocite

Atomic force microscopy (AFM) has been applied to study the adsorption morphology of various collectors, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX) and Cytec Aerofloat 238 (sodium dibutyl dithiophosphate), on chalcocite in situ in aqueous solutions. The AFM images show that all these collectors adsorb strongly on chalcocite. Xanthate adsorbs mainly in the form of insoluble cuprous xanthate (CuX), which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This xanthate/chalcocite adsorption mechanism is very similar to the one obtained with the xanthate/bornite system; while it is different from the one of the xanthate/chalcopyrite systems, for which oily dixanthogen is the main adsorption product on chalcopyrite surface. On the other hand, dibutyl dithiophosphate adsorbs on chalcocite in the form of hydrophobic patches, which can be removed by rinsing with ethanol alcohol. AFM images show that the adsorption of collectors increases with increasing adsorption time and collectors’ concentration. In addition, increasing the solution pH to 10 does not prevent the adsorption of xanthate and Aerofloat 238 on chalcocite and the result is in line with the fact that chalcocite floats well in a wide pH range up to 12 with xanthate and dialkyl dithiophosphate being used as collectors. The blending collectors study shows that xanthate and dialkyl dithiophosphate can co-adsorb with both insoluble cuprous xanthate and oily Cu(DTP)2 (Cu dibutyl dithiophosphate) on a chalcocite surface. The present study helps to clarify the flotation mechanism of chalcocite in industry practice using xanthate and dialkyl dithiophosphate as collectors.

Flotation separation of molybdenite from chalcopyrite using mechanically degraded polyacrylamide as a novel depressant

In this work, cationic polyacrylamide (CPAM) which was degraded by mechanical shear was used as a chalcopyrite potential selective depressant to separate molybdenite from chalcopyrite by flotation while using kerosene as a collector. Micro-flotation experiments of single minerals show that CPAM was the most suitable to be used as the chalcopyrite depressant among the three different types of polyacrylamide. The molecular weight of CPAM was reduced from 12 million to 1.8 million and the depression performance of CPAM on chalcopyrite was increased after mechanical rotational shear degradation for 6 h. When the dosage of CPAM which was degraded by mechanical shear for 6 h (CPAM-6 h) was 6.0 mg/L, good separation results were achieved in the artificially mixed minerals experiment. In froth products, the recovery of molybdenite was 87.96 %, the grade of molybdenum was 54.60 %, and the grade of copper was only 2.58 %. The depression mechanism of CPAM-6 h on chalcopyrite and molybdenite was systematically investigated by contact angle measurement, zeta potential measurements, FT-IR spectra analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The analysis results show that CPAM-6 h has not only electrostatic adsorption but also chemical adsorption on the surface of chalcopyrite while only electrostatic adsorption on molybdenite, then the addition of kerosene can destroy the hydrogen bonding of CPAM-6 h on the surface of molybdenite and make it hydrophobic again, but kerosene cannot remove the copper-ammonium complex formed by CPAM-6 h on the surface of chalcopyrite, therefore, chalcopyrite remains hydrophilic.

Selective flotation of chalcopyrite from galena using a novel collector benzoic diethylcarbamothioic thioanhydride: An experimental and theoretical investigation

The flotation separation of chalcopyrite and galena has always been the focus of production. Benzoic diethylcarbamothioic thioanhydride (BDT) is a novel chelating collector that has shown a certain application strength in the field of sulfide ore flotation. In this research, micro-flotation tests, zeta potential tests, Fourier transform infrared spectroscopy measurements, X-ray photoelectron spectroscopy measurements, and density functional theory (DFT) calculations were used to investigate the selective recovery and selective adsorption of BDT on chalcopyrite and galena. The flotation results showed that BDT had good flotation selectivity for chalcopyrite and galena, which achieved up to 96.67 % and 50.26 %, respectively, at pH 6 using a collector dosage of 100 g/t. The analysis of the adsorption mechanism showed that CS and CO in BDT are mainly involved in the adsorption process. On the surface of chalcopyrite, CS and CO can form a six-membered chelating ring with Fe or Cu sites. BDT can also be adsorbed on the surface of galena in the same way, but the adsorption strength is weaker than that on the surface of chalcopyrite.

Effect of sodium metabisulfite and slaked lime on the floatability and surface properties of chalcopyrite

In the flotation of complex copper ores containing chalcopyrite in seawater, sodium metabisulfite (SMBS) has been widely used as a pyrite depressant. Here, calcium ions in seawater or in process water because of pH control using lime (CaO) or slaked lime (Ca(OH) 2 ) can affect the floatability of chalcopyrite. However, the effect of SMBS on the floatability of chalcopyrite in the presence of calcium ions is unknown. Therefore, the current study investigated the flotation behavior and surface properties of chalcopyrite after treatment with SMBS in the absence and presence of Ca(OH) 2 . The flotation experiments demonstrated that both SMBS treatment and the addition of Ca(OH) 2 exhibited a depressing effect on the natural floatability of chalcopyrite. This depressing effect of SMBS and Ca(OH) 2 on the floatability of chalcopyrite was significantly decreased in the presence of potassium amyl xanthate (PAX). However, the combination of SMBS treatment and Ca(OH) 2 formed calcium sulfite (CaSO 3 ) on the surface of chalcopyrite, which significantly reduced the recovery of chalcopyrite from 97% to 66% when in the presence of PAX and at a pH of 9. • The effect of Na 2 S 2 O 5 (SMBS) and Ca(OH) 2 on the floatability of chalcopyrite was studied. • Both SMBS and Ca(OH) 2 exhibited a depressing effect on the recovery of chalcopyrite. • SMBS produced sulfate and hydrophilic species on the surface of chalcopyrite. • SMBS and Ca(OH) 2 form CaSO 3 precipitate that reduced the recovery of chalcopyrite. • SMBS reduced the adsorbed PAX on the surface of chalcopyrite.

Synthesis of novel thionocarbamate for copper−sulfur flotation separation and its adsorption mechanism

As a novel collector, O-isopropyl-N,N-diethyl thionocarbamate (IPDTC) was designed and synthesized for copper−sulfur flotation separation. Density functional theory calculations were performed to investigate the electronic structures of IPDTC. The results showed that IPDTC had higher energy of the highest occupied molecular orbital but lower electronegativity than O-isopropyl-N-ethyl thionocarbamate (Z−200). It was predicted that IPDTC had strong collection ability according to the reaction energy criteria. Flotation results demonstrated that the collecting ability of IPDTC to chalcopyrite and pyrite was stronger than that of Z−200. Then, the flotation mechanism was analyzed by measurements of surface tension, adsorption capacity, XPS, FTIR and zeta potential. These results indicated that IPDTC could reduce the solution surface tension. The adsorption capacity of IPDTC on chalcopyrite was higher than that on pyrite, consistent with the results of the flotation tests. FTIR, zeta potential and XPS results also demonstrated that IPDTC was strongly absorbed on the chalcopyrite surface by formation of Cu—S—C bonds, but showed a weak affinity on the pyrite surface.

A molecular analysis on nitrile-based collectors and their application to chalcopyrite flotation

In this research, one of the newest nitrile-based collectors so-called Tecflote-S10, was re-structured to increase its application in the flotation of copper-bearing sulfide minerals. For this purpose, a systematic theoretical study was conducted using a self-consistent periodic density functional theory (DFT) calculation to identify the adsorption properties of several new-designed nitrile-based collectors on the chalcopyrite (100) surface. In the new collector design, the long hydrocarbon chain of the Tecflote-S10 was replaced with a phenyl ring having several functional groups in different positions to address the electron-donating effect on the strength of the adsorption. The electronic properties and reactivity of new-designed collectors were evaluated, and a proper synthesis route was proposed. Collector-surface interaction and adsorption efficiency of new collectors on chalcopyrite surface were investigated using adsorption energy, the Fukui function (FF), and partial density of state (PDOS) analyses. It was found that replacing phenyl ring in the collector structure instead of a long hydrocarbon chain lead to an improvement in the collector adsorption efficiency. Accordingly, all new-designed collectors showed higher adsorption ability on chalcopyrite than the Tecflote-S10. However, collectors with the acronyms Tf(Ph)-3-R5, Tf(Ph)-N-2R1, and Tf(Ph)-N-2R2 with higher adsorption energies compared to others could be potentially used as a proper alternative in chalcopyrite flotation. To verify the results experimentally, futuristic adsorption, wettability, and floatability tests will be examined for this study.

Depression mechanism of peracetic acid for flotation separation of chalcopyrite from arsenopyrite based on coordination chemistry

A highly selective depressant is of critical importance for efficient Cu-As separation. Herein, the depression mechanism of peracetic acid (PAA) with respect to arsenopyrite is systematically analysed at the microscopic level using density functional theory calculations, molecular dynamics simulations, X-ray photoelectron spectroscopy and coordination chemistry. The adsorption energy of PAA on FeAsS (001) surfaces is − 550.5 kJ/mol. Both, the single-bonded O (O1) and double-bonded O (O2) atoms of PAA are simultaneously adsorbed onto the Fe atoms of the FeAsS (001) surfaces, but the covalent bond formed by the O1 and Fe atoms is more stable. Oxidised arsenopyrite surfaces contain an abundance of Fe(III)-O species, while the state of the Cu and Fe atoms on the chalcopyrite surface does not change significantly. The σ-coordination effect of the PAA molecules is more likely to provide lone-pair electrons to the empty eg orbital of the Fe2+ ions on the surface of arsenopyrite than to those on chalcopyrite surfaces. The three pairs of π-electrons in the t2g orbital of the Fe2+ ions on arsenopyrite surfaces are more likely to interact with the empty π-orbital of the PAA molecule in a π-backbonding interaction.

Underlying synergistic collection mechanism of an emerging mixed reagent scheme in chalcopyrite flotation

Effective collectors are essential for the flotation of copper sulphide resources. In this work, we prepared a novel surfactant containing C-O-C groups, O,O'-bis(2-butoxyethyl) ammonium dithiophosphate (BEAT), and mixed it with O-isopropyl-N-ethyl thionocarbamate (IPETC) as an emerging reagent scheme for efficiently improving the flotation recovery of chalcopyrite. Foaming performance tests revealed that BEAT possessed a stronger foaming ability and foam stability than methyl isobutyl carbinol (MIBC). Micro-flotation results indicated that a significant improvement of chalcopyrite flotation recovery of 92.43% was achieved when mixed IPETC/BEAT collectors (BEAT optimal molar fraction of 60%) of 4 × 10−5 mol/L at pH 7.0–7.5 were employed. Bench-flotation results of copper sulphide ores showed that compared with IPETC + MIBC (30 g/t + 36 g/t) or BEAT (30 g/t) alone reagent system, a smaller amount of mixed IPETC/BEAT collectors (only 20 g/t) scheme was able to obtain higher Cu recovery and Cu grade. Surface tension results implied that the mixtures provided higher surface activity than individual IPETC, thus exhibiting superior foaming properties and better water solubility. Wettability results suggested that mixed collectors possessed stronger hydrophobicity and superior selectivity towards chalcopyrite against pyrite than single collector. FTIR results demonstrated that mixed collectors were chemically involved with the chalcopyrite surface through co-adsorption. Intermolecular interaction parameter computation confirmed the positive synergistic effect of mixed collectors.

Cryo-ToF-SIMS study of sodium isobutyl xanthate adsorption on sulfide minerals

The chemical properties of the mineral/solution interface have a decisive influence on the flotation behavior of minerals. Here, chalcopyrite, chalcopyrite-pyrite mixture, and chalcopyrite-galena mixture were reacted in 0.1 mM sodium isobutyl xanthate solution at natural pH, then centrifuged, fast-frozen, and characterized with time-of-flight secondary ion mass spectrometry at –125 °C (Cryo-ToF-SIMS) in comparison with the samples thawed in vacuum and measured at room temperature (RT-ToF-SIMS). Cryo-ToF-SIMS of fast-frozen mineral wet pastes allows quasi-in situ characterization of chemical species within the mineral/solution interfacial layer. It was found that dixanthogen was the predominant species of xanthate adsorption products on chalcopyrite and pyrite, while that of galena was lead isobutyl xanthate. In particular, due to the interaction effects between sulfide minerals, the formation of dixanthogen at the mineral/solution interface of chalcopyrite was promoted and inhibited by pyrite and galena, respectively, and the lead ions dissolved from galena were adsorbed to the chalcopyrite surface, resulting in xanthate to react with adsorbed species of lead ions to form lead isobutyl xanthate. This study also observed that the mineral/solution interfacial layer of chalcopyrite-galena mixture was more deficient in sodium ions and calcium ions than those of chalcopyrite and chalcopyrite-pyrite mixture; we proposed that this phenomenon was caused by the repulsion of sodium ions and calcium ions by lead ions dissolved from galena in the electric double layer of minerals.

Surface Passivation and Detrimental Heat-Induced Diffusion Effects in RbF-Treated Cu(In,Ga)Se2 Solar Cell Absorbers.

Alkali postdeposition treatments of Cu(In,Ga)Se2 absorbers with KF, RbF, and CsF have led to remarkable efficiency improvements for chalcopyrite thin film solar cells. However, the effect of such treatments on the electronic properties and defect physics of the chalcopyrite absorber surfaces are not yet fully understood. In this work, we use scanning tunneling spectroscopy and X-ray photoelectron spectroscopy to compare the surface defect electronic properties and chemical composition of RbF-treated and nontreated absorbers. We find that the RbF treatment is effective in passivating electronic defect levels at the surface by preventing surface oxidation. Our X-ray photoelectron spectroscopy (XPS) data points to the presence of chemisorbed Rb on the surface with a bonding configuration similar to that of a RbInSe2 bulk compound. Yet, a quantitative analysis indicates Rb coverage in the submonolayer regime, which is likely causing the surface passivation. Furthermore, ab initio calculations confirm that RbF-treated surfaces are less prone to oxidation (in the form of Ga, In, and Se oxides) than bare chalcopyrite surfaces. In addition, elemental diffusion of Rb along with Na, Cu, and Ga is found to occur when the samples are annealed under ultrahigh vacuum conditions. Magnetic sector secondary ion mass spectrometry measurements indicate that there is a homogeneous spatial distribution of Rb on the surface both before and after annealing, albeit with an increased concentration at the surface after heat treatment. Depth-resolved magnetic sector secondary ion mass spectrometry measurements show that Rb diffusion within the bulk occurs predominantly along grain boundaries. Scanning tunneling and XPS measurements after subsequent annealing steps demonstrate that the Rb accumulation at the surface leads to the formation of metallic Rb phases, involving a significant increase of electronic defect levels and/or surface dipole formation. These results strongly suggest a deterioration of the absorber-window interface because of increased recombination losses after the heat-induced diffusion of Rb toward the interface.

A Quantitative Relationship between Oxidation Index and Chalcopyrite Flotation Recovery

The surface oxidation of chalcopyrite is one of the most important factors affecting its flotation performance. In this study, a critical oxidation degree is proposed to define “slight” and “significant” oxidation in terms of surface species and chalcopyrite flotation recovery. Slight oxidation enhanced chalcopyrite hydrophobicity, but significant oxidation reduced its recovery apparently. Microthermokinetic measurements indicated that the apparent activation energy (Ea) of chalcopyrite oxidation was reduced from around 173 kJ·mol−1 to 163 kJ·mol−1 when the reaction changed from slight oxidation to significant oxidation when applying H2O2. The surface oxidation degree was defined as the ratio of hydrophilic species to hydrophobic species. The highest recovery (94.8%) and contact angle (93°) were achieved at a concentration of 0.1 vol.% H2O2, with the lowest oxidation degree of 0.388 being observed. The oxidation degree was correlated to the flotation recovery, with a quantitative relationship (y = −298.81x + 213.05, y and x represent flotation recovery and oxidation degree, respectively, 0.388 ≤ x ≤ 0.618) being established, thereby giving a guideline to better manage chalcopyrite flotation by controlling its surface oxidation and SBX adsorption on chalcopyrite surfaces.

Effect of calcium ions on surface properties of chalcopyrite and arsenopyrite and its response to flotation separation under low-alkalinity conditions

Herein, the effect of calcium ions on surface properties of chalcopyrite and arsenopyrite and its response to flotation separation under low-alkalinity conditions were investigated by flotation tests, zeta potential measurements, solution chemistry analysis, XPS tests, and DFT calculations. The flotation test results showed that calcium ions can selectively decrease the arsenopyrite floatability. The analysis results of zeta potential and solution chemistry showed that the positively charged Ca2+ and Ca(OH)+ were adsorbed on the chalcopyrite and arsenopyrite surfaces, and more adsorption of which on the arsenopyrite surface was found. Furthermore, the pre-adsorption of calcium ions greatly hindered the collector adsorption on the arsenopyrite surface while did not hinder that on the chalcopyrite surface. The XPS test results further demonstrated that CaOH+ was covered on the arsenopyrite surface via interaction with the Fe atom and S atom. Moreover, DFT calculation results revealed that the Ca-S bond can form on the chalcopyrite surface while the Fe-O bond cannot form. However, the Fe-O bond and Ca-S bond were both formed on the arsenopyrite surface, and the formed Ca-S bonds on the chalcopyrite surface were weaker than that on the arsenopyrite surface. Thus, a more hydrophilic surface of arsenopyrite was generated, which decreased its floatability.

Effect of deep oxidation of chalcopyrite on surface properties and flotation performance

In this study, chalcopyrite was oxidized in hydrogen peroxide (H 2 O 2 ) solutions of different concentrations to simulate different degrees of oxidation in real ores, and the effects of H 2 O 2 treatment on chalcopyrite surface properties and flotation performance were investigated by surface analysis techniques and floatation experiments, which implied the reason for the poor grade and recovery of oxidized chalcopyrite concentrate in the production process of the ore. Flotation results showed that when the concentration of H 2 O 2 increased from 0% (by weight) to 5%, the flotation recovery of chalcopyrite decreased sharply. However, with increasing H 2 O 2 concentration from 5% to 30%, chalcopyrite recovery improved relatively to different degrees with different collector concentrations. Analyses of X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic optical emission spectrophotometry (ICP-OES) results indicated that the pretreatment with H 2 O 2 caused that hydrophilic substance formed on chalcopyrite surface with the dissolution of copper ions, and the dissolution amount of copper increased with the increase of H 2 O 2 concentration. UV–visible spectrophotometer and Fourier Transform Infrared spectrum (FTIR) studies indicated that the pretreatment of chalcopyrite with H 2 O 2 had little effect on the adsorption amount of potassium butyl xanthate (PBX) on chalcopyrite surface. However, due to the dissolution of copper ions, PBX interacted with chalcopyrite mainly as buthyl dixanthogen (BX) 2 .

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.

Effect of residual reagents on chalcopyrite losses at Mount Isa Mines copper Operation: Part II - evaluation of flotation mechanisms

Mount Isa Mines Copper Operation (MICO) is one of the largest copper producers in Australia. The concentrator has a complex circuit, which includes a pre-flotation section designed for early removal of deleterious talc, and other naturally floating gangue including carbonaceous material.The downside of early talc removal is the loss of chalcopyrite to the pre-flotation concentrate. This work investigates the role of residual collector and frother reagents on chalcopyrite losses in the MIM pre-flotation circuit, and the possibility of improving talc recoveries whilst keeping chalcopyrite loss to a minimum. In Part I of this study, it was demonstrated that talc/chalcopyrite selectivity can be improved by removing residual reagents from the MIM process water. In Part II, the mechanisms of chalcopyrite losses are evaluated to explain the results presented in Part 1. This is done through an evaluation of mineral recoveries by true flotation and entrainment. The effect of residual reagents on chalcopyrite surfaces is evaluated using statistical analysis of Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) performed on process stream samples.