Copper Precipitation Research Articles

Optimization of Copper-Ammonia-Sulfate Electrolyte for Maximizing Cu(I):Cu(II) Ratio Using pH and Copper Solubility

An investigation has been carried out to understand the solution chemistry of the Cu-NH−-SO4−2 system, focusing on the effect of pH on the solubility of copper in the solution and maximizing the Cu(I):Cu(II) ratio. A Pourbaix diagram for the Cu-N-S system has also been created using the HSC Chemistry software for a wide range of Cu-NH3 species, unlike most other studies that focused only on Cu(NH3)42+ and Cu(NH3)52+ (Cu(II)) as the dominant species. The Pourbaix diagram demonstrated that the Cu(I) exists as Cu(NH3)2+, while the Cu(II) species are present in the system as Cu(NH3)42+ and Cu(NH3)52+, depending upon the Eh and pH of the solution. Copper precipitation was observed in the electrolyte at pH values less than 8.0, and the precipitation behavior increased as the pH became acidic. The highest Cu(I):Cu(II) ratio was observed at higher pH values of 10.05 due to the higher solubility of copper at higher alkaline pH. The maximum Cu(II) concentration can be achieved at 4.0 M NH4OH and 0.76 M (NH4)2SO4. In the case of low pH, the highest Cu(I):Cu(II) ratio obtained was 0.91 against the 4.0 M and 0.25 M concentrations of NH4OH and (NH4)2SO4, respectively. Meanwhile, at high pH, the maximum Cu(I):Cu(II) ratio was 15.11 against the 0.25 M (NH4)2SO4 and 4.0 M NH4OH. Furthermore, the low pH experiments showed the equilibrium constant (K) K < 1, and the high pH experiments demonstrated K > 1, which justified the lower and higher copper concentrations in the solution, respectively.

Structural characteristics and biological evaluation of copper coating cotton material obtained by chemical reduction method

The article describes the preparation of new cotton materials obtained by chemical deposition of copper sulfide. This two-stage process consists of chelation of copper sulfate on cellulose chains of cotton (COT → COT-CuSO4) with subsequent precipitation of copper in the form of copper sulfide (COT-CuSO4 → COT-CuS) using sodium sulfide. The obtained COT-CuS composites were characterized physicobiologically. Thus, the structural characteristic of the Cotton-CuS material was determined by microscopy analysis (SEM), Atomic Absorption Spectrometry with Flame Excitation (FAAS), specific surface area and total pore volume analysis (BET). The copper functionalized cotton fabric was subjected to microbial activity tests against colonies of Gram-negative (Escherichia coli) and Gram-positive ( Staphylococcus aureus) bacteria and Chaetomium globosum, Aspergillus niger fungal molds species. Biochemical evaluation includes hematological tests of activated partial thromboplastin time (aPTT) and prothrombin time (PT). The substantial antimicrobial properties of the newly synthesized COT-CuS material with the lack of influence on blood coagulation processes offer prospects of a potential use as applications as an antibacterial/antifungal material.

Hydrothermal precipitation of copper from leaching solutions of metallurgical dusts

In this work, we aim to establish the main regularities of hydrothermal precipitation of copper from the previously unstudied sulfuric-nitric acid and sulfate solutions of atmospheric and autoclave processing of metallurgical dusts. Pyrite was used as a sulfidizer. The elemental composition of the products was determined by X-ray fluorescence, inductively coupled plasma atomic emission spectrometry, and atomic absorption analysis. It was found that copper precipitation by the proposed technology enables its recovery at a level of more than 95%. For sulfate solutions with a high arsenic concentration, a two-stage scheme of oxidation-hydrothermal treatment with the following parameters was proposed: temperature 180°С, duration 2 h, oxygen consumption 0.026 dm3/g pyrite (for the 1st stage), and 200°С and 2 h (for the 2nd stage). Extraction in the cake amounted to 95.4% of copper (in the form of Cu2S) and 91.4% of arsenic (in the form of FeAsO4), which allowed further separation of these metals by flotation. An autoclave treatment of a Cu–Zn–Fe–As–NO3 solution in the presence of pyrite at 180–220°С produced the activation energy values (kJ/mol) corresponding to the kinetic regime calculated by the two methods: 64.6 by the conventional method and 60.5 by the shrinking core model. The kinetic parameters of CuSO4–H2SO4–FeS2–H2O and CuNO3–H2SO4–FeS2–H2O systems were also determined. Flotation enrichment of copper autoclave precipitation cake was shown to result in a high degree of Cu and As separation, with the recovery amounting to Cu ˃ 95% and As ˂ 5%. Precious metals contained in pyrite are transferred to a flotation concentrate by 92.7% (Au) and 96.5% (Ag). The composition of the resulting flotation concentrate comprised (%): 12 Cu; 37 Fe; 38 S; 13 other elements. It is shown that, in order to obtain a product with the required content of copper, flotation concentrate should be separated into pyrite and copper concentrates followed by an additional flotation of primary copper concentrate in an alkaline medium in the presence of lime. Hence, our study has established the main regularities of hydrothermal precipitation of copper from the sulfuric-nitric acid and sulfate solutions of atmospheric and autoclave processing of metallurgical dusts.

Replacive IOCG systems in the Ossa Morena Zone (SW Iberia): The role of pre-existing ironstones as a geochemical trap

The central Ossa Morena Zone (SW Iberia) hosts a regionally extensive ironstone level interbedded with bimodal volcanic rocks, limestone and shale of Lower-Middle Cambrian age. The stratabound ironstone includes dominant magnetite and hematite with locally abundant chert and barite. It is interpreted as being (sub-)exhalative at or near the seafloor and formed during a rifting event that postdated the Cadomian orogeny. In some places, such as in the Las Herrerías deposit, the ironstone is irregularly replaced by a chalcopyrite-rich ore; the Cu-rich mineralization is accompanied by the pervasive phyllic alteration of the hosting siliciclastic sediments. The highest copper grades are found when the ironstone is crosscut by WNW-ESE-trending late-Variscan extensional brittle-ductile structures that are interpreted as the feeder channels for deep hydrothermal fluids. A similar nearby copper-rich mineralization (Pallares) is is likely controlled by the tectonic contact between limestone and pyrite-rich black shale.Sr-Nd whole-rock isotope geochemistry data suggests that the Sr in the ironstone (87Sr/86Sri ≈ 0.7088) is close to isotopic equilibrium with the local exhalative barite (0.7084–0.7086) and Cambrian seawater. The ironstone has a significantly more crustal εNd initial signature (<-1.8) than the coeval volcanic rocks (+5.2 to + 7.9). The younger sulfide mineralization inherited the Nd isotope composition of the ironstone but shows a significant enrichment in 87Sr (87Sr/86Sr > 0.7091) that is interpreted as related with the input of genetically different and more crustally-derived hydrothermal fluids.39Ar-40Ar dating of the phyllic alteration suggest that the copper mineralization was formed at ca. 332–330 My. These ages are coeval with those of small peraluminous granite intrusions that host Cu-Au vein-like mineralization and dated at 331.8 ± 1.6 Ma (LA ICPMS U-Pb zircon). Our interpretation is that the copper-rich mineralization at the Las Herrerías area is the distal expression of an intrusion-related hydrothermal system.Numerical modelling shows that ironstone is an effective trap for copper precipitation due to the large changes in pH and fO2 that take place when copper-bearing acid and reduced fluids react with the brittle ironstone. The precipitation of chalcopyrite, however, is controlled by the amount of available reduced sulfur in the ore trap. The δ34S values of the sulfides (+12.6 to + 21.6 ‰) suggest that the most likely source for the reduced sulfur is the thermogenic reduction of aqueous sulfate equilibrated with the exhalative barite (δ34S, +31.4 to + 35 ‰) with some minor input of reduced sulfur leached from the metasediments.This system could be considered as a variant of the IOCG clan. The formation of the ironstone and the copper mineralization, however, are separated by more than 200 My. Probably, many IOCG systems have a similar origin as Las Herrerías, with an ironstone being just a passive geochemical trap for the copper–gold mineralization.

Особливості структуроутворення заевтектоїдних сталей, легованих міддю

The structural state of pre-eutectoid steels alloyed with copper in the range of up to 28% was studied. It was established that the alloying of steel with a carbon content of 1.3% with copper in the amount of 8, 12 and 28% leads to the formation of the primary and secondary copper -phase The main metallic component of the structure of the studied copper-alloyed steels is represented by thin-plate copper pearlite with inclusions on the boundaries of the primary austenite grains of secondary cementite and secondary inclusions of the copper -phase. The results of the X-ray spectral microanalysis showed that the primary copperite of the -phase consists of 92.5% of copper and 7.1% of iron. The transition zone between the primary copper precipitate and the matrix, the distribution of chemical elements in it, was studied. The total size of the interphase zone is 0.4 μm. It was established that alloying of steels with 8-28% copper contributes to the formation of a highly dispersed structure of copper thin-plate pearlite, as well as the formation of areas with deformed microvolumes near the primary copper e-phase, which constitute a significant barrier to the movement of dislocations. Thus, a state with increased resistance to dynamic loads has been formed at the micro level. The obtained results open up the possibility of using post-eutectoid steels alloyed with copper in the corresponding highly loaded products Keywords: structure, post-eutectoid steel, alloying, thin-plate pearlite, e-phase, iron, spectrum.

Multi-million-year magmatic and hydrothermal activity is key to the formation of supergiant to behemothian porphyry copper deposits

Understanding the primary controls on mineral deposit formation and size is essential for sourcing the metals required by our ever-growing economy. The tonnage of porphyry copper deposits ranges five orders of magnitude but the key mechanisms and processes that modulate the size of these deposits remain enigmatic. Here, we investigate the behemothian deposits of the Chuquicamata Intrusive Complex (CIC) in northern Chile employing high-precision U–Pb and Re–Os geochronology. We resolve a complex long-lived magmatic-hydrothermal activity that lasted over 3.3 Myr. High-precision zircon petrochronology data indicate two distinct porphyry emplacement episodes, separated by 0.5 Myr, with the younger generation closely tied to the main intervals of hydrothermal mineralization. High-precision Re–Os molybdenite dates reveal a prolonged hydrothermal mineralization interval (> 2.5 Myr) that progressively migrated southwards within the CIC and continued after the end of the (apparent) magmatic activity. We show that the rate of copper precipitation varies little in nature (0.025–0.10 Mt/kyr) and is independent of the size of the deposit. Consistent with evidence from smaller deposits, our findings provide unprecedented evidence that copper endowment in porphyry copper deposits positively correlates with the timescales of magmatic and hydrothermal activity. Supergiant to behemothian deposits require multi-million-year magmatic-hydrothermal activity, linking the largest porphyry copper systems to a simple metric – the duration of magmatic-hydrothermal activity.

A New Cu-Alloyed Precipitation-Hardening Hot-Work Tool Steel

Abstract Hot-work tools for hot forming processes, such as die forging, are subject to complex loads that can often lead to premature tool failure. The present study attempts to reduce the main cause of failure of high-speed hot working tools, i. e., wear due to surface breakdown, with the aid of damage-tolerant microstructures. For this purpose, a hot-work tool steel is specifically alloyed with copper in order to form copper precipitations during the subsequent heat treatment, which increase the strength of the material and contribute to the reduction of dislocation movements. The aim is to close the property gap between the standardized direct-hardening and secondary-hardening hot-work tool steels.

Study on the mechanism of copper and arsenic separation in copper smelting acidic solution by arsenic sulfide residue

A large amount of acidic solution containing arsenic and copper is produced in the hydrometallurgical treatment process of arsenic-containing solid waste in copper smelting. It is necessary to develop an economical and efficient separation technology of arsenic and copper from the solution. In this paper, according to the difference of solubility product between As2S3 and CuS, arsenic sulfide residue (ASR) was used as copper precipitant to realize the efficient separation of copper and arsenic in acidic solution, so as to achieve the purpose of “treating waste with waste”. It is found that the copper precipitation reaction is a more sensitive reaction. With the increase of temperature and time, the precipitation efficiency of copper first increases and then decreases, mainly because CuS will react with AsO43- in the solution, and then re-dissolution occurs. With the increase of pH value, As and Fe precipitate, resulting in incomplete separation of Cu and As. Under the optimum conditions, the precipitation efficiencies of Cu, Sb, Cd, Fe and Zn reached 97.39 %, 46.31 %, 2.04 %, 2.59 % and 0.65 %, respectively. The content of Cu in the precipitated residue reaches 50.47 wt%. The precipitated residue can be used as raw material for copper smelting.

Copper sulfide precipitation from alkaline monosodium glutamate solutions

Recent studies of metal leaching using monosodium glutamate have shown promising results of this being an alternative to conventional leaching reagents. However, limited information is available covering the treatment of leaching solutions and the final recovery of metals. In this regard, this article presents an experimental study on the precipitation of copper from glutamate solutions using sodium hydrosulfide (NaHS), as a simple and efficient route for the processing of leaching solutions from this new system. Synthetic pregnant leach solutions (PLS) with varying copper total concentrations [CuT] and glutamate concentrations were used. The effects of [CuT], [CuT]:[NaHS] molar ratio and glutamate concentration on the particle size distribution and copper recovery were investigated. The results revealed that higher [CuT] led to smaller particle sizes, with the P90 decreasing from 106 µm to 60.7 µm and 73.2 µm for Cu concentrations of 1 g/L, 2.5 g/L, and 5 g/L, respectively. The [CuT]:[NaHS] molar ratio reduced the P90 particle size, from 60.7 µm to 56.4 µm and 7.44 µm as the molar ratio increased from 1:0.8 to 1:1 and 1:1.2, respectively. Copper recovery from glutamate solutions increased with higher molar ratios, achieving values of 70.95 %, 88.24 %, and 99.55 % for molar ratios of 1:0.8, 1:1, and 1:1.2, respectively, agreeing with copper recovery values of other chemical systems. The glutamate concentration had minimal impact on particle size but affected copper recovery, with a decrease from 88.24 % to 85.83 % when increasing the glutamate concentration from 0.5 M to 1 M. X-ray diffraction (XRD) analysis confirmed the presence of pure covellite with hexagonal phase in the precipitates. These findings contribute to understanding copper precipitation dynamics from glutamate solutions using NaHS and have implications for optimizing copper recovery processes in the perspectives of the advent of alkaline leaching of copper ores.

Utilization of organic-rich materials for the adsorption of copper ions from aqueous environments

This study investigated the suitability of moss peat and compost as adsorbents for removing copper ions from aqueous systems. Kinetic experiments were conducted at pH 4, 20 °C, and an initial copper ion concentration of 20 mM. Under these experimental conditions, moss peat and compost had a maximum adsorption capacity of 45.8 and 41.9 mg/g, respectively. The kinetic data was assessed using several models, and the data fitted well with the pseudo-second-order model for both adsorbents. Moreover, the analysis of the isotherm data showed that the Langmuir model could fit the data, suggesting that copper ions are chemically adsorbed onto moss peat and compost. The pH value of 4.5 was the most effective for the adsorption of copper ions onto moss peat and compost. At this pH value, the maximum adsorption capacities were 60.0 mg/g for moss peat and 56.9 mg/g for compost. The characterization of moss peat and compost before and after the interaction with copper ions indicated that surface precipitation was the dominant mechanism by which copper ions were removed from aqueous systems. Copper precipitation on the surface of moss peat was higher than that on the surface of compost, and it was found to be 7.7 wt% and 3.8 wt%, respectively. Overall, these findings highlight the potential of using moss peat and compost as effective adsorbents for copper ions in highly contaminated water, particularly industrial and mining effluent.

Anaerobic treatment of groundwater co-contaminated by toluene and copper in a single chamber bioelectrochemical system

Addressing the simultaneous removal of multiple coexisting groundwater contaminants poses a significant challenge, primarily because of their different physicochemical properties. Indeed, different chemical compounds may necessitate establishing distinct, and sometimes conflicting, (bio)degradation and/or removal pathways. In this work, we investigated the concomitant anaerobic treatment of toluene and copper in a single-chamber bioelectrochemical cell with a potential difference of 1 V applied between the anode and the cathode. As a result, the electric current generated by the bioelectrocatalytic oxidation of toluene at the anode caused the abiotic reduction and precipitation of copper at the cathode, until the complete removal of both contaminants was achieved. Open circuit potential (OCP) experiments confirmed that the removal of copper and toluene was primarily associated with polarization. Analogously, abiotic experiments, at an applied potential of 1 V, confirmed that neither toluene was oxidized nor copper was reduced in the absence of microbial activity. At the end of each experiment, both electrodes were characterized by means of a comprehensive suite of chemical and microbiological analyses, evidencing a highly selected microbial community competent in the biodegradation of toluene in the anodic biofilm, and a uniform electrodeposition of spherical Cu2O nanoparticles over the cathode surface.

Apatite as a Record of Magmatic–Hydrothermal Evolution and Metallogenic Processes: The Case of the Hongshan Porphyry–Skarn Cu–Mo Deposit, SW China

Apatite, as a common accessory mineral found in magmatic–hydrothermal deposits, effectively yields geochemical insights that facilitate our understanding of the mineralization process. In this research, multiple generations of magmatic and hydrothermal apatite were observed in the Hongshan porphyry–skarn Cu–Mo deposit in the Yidun Terrane in SW China. The geochemical compositions of the apatite were studied using in situ laser ablation–inductively coupled plasma mass spectrometry and an electron probe microanalysis to understand the magmatic–hydrothermal processes leading to ore formation. The apatite (Ap1a) occurs as subhedral to euhedral inclusions hosted in the phenocrysts of the granite porphyry. The Ap1b occurs later than Ap1a in a fine-grained matrix that intersects the earlier phenocrysts. Increases in F/Cl, F/OH, and F/S and decreases in ΣREE and (La/Yb)N from Ap1a to Ap1b suggest the exsolution of a volatile-rich phase from the magma. The skarn hosts three types of hydrothermal apatite (Ap2a, Ap2b, and Ap3), marking the prograde, retrograde, and quartz–sulfide stages of mineralization, respectively. The elemental behaviors of hydrothermal apatite, including the changes in Cl, Eu, As, and REE, were utilized to reflect evolutions in salinity, pH, oxygen fugacity, and fluid compositions. The composition of Ap2a, which occurs as inclusions within garnet, indicates the presence of an early acidic magmatic fluid with high salinity and oxygen fugacity at the prograde skarn stage. The composition of Ap2b, formed by the coupled dissolution-reprecipitation of Ap2a, indicates the presence of a retrograde fluid that is characterized by lower salinity, higher pH, and a significant decrease in oxygen fugacity compared to the prograde fluid. The Ap3 coexists with quartz and sulfide minerals. Based on studies of Ap3, the fluids in the quartz–sulfide stage exhibit relatively reducing conditions, thereby accelerating the precipitation of copper and iron sulfides. This research highlights the potential of apatite geochemistry for tracing magmatic–hydrothermal evolution processes and identifying mineral exploration targets.

Hydrogenation of Carbon Dioxide to Dimethyl Ether on CuO–ZnO/ZSM-5 Catalysts: Comparison of Powder and Electrospun Structures

The promising direct dimethyl ether (DME) production through CO2 hydrogenation was systematically analyzed in this research by synthesizing, characterizing, and testing several catalytic structures. In doing so, various combinations of precipitation and impregnation of copper- and zinc-oxides (CuO–ZnO) over a ZSM-5 zeolite structure were applied to synthesize the hybrid catalysts capable of hydrogenating carbon dioxide to methanol and dehydrating it to DME. The resulting catalytic structures, including the co-precipitated, sequentially precipitated, and sequentially impregnated CuO–ZnO/ZSM-5 catalysts, were prepared in the form of particle and electrospun fibers with distinguished chemical and structural features. They were then characterized using XRD, BET, XPS, ICP, TGA, SEM, and FIB-SEM/EDS analyses. Their catalytic performances were also tested and analyzed in light of their observed characteristics. It was observed that it is crucial to establish relatively small-size and well-distributed zeolite crystals across a hybrid catalytic structure to secure a distinguished DME selectivity and yield. This approach, along with other observed behaviors and the involved phenomena like catalyst particles and fibers, clusters of catalyst particles, or the whole catalytic bed, were analyzed and explained. In particular, the desired characteristics of a CuO–ZnO/ZSM-5 hybrid catalyst, synthesized in a single-pot processing of the precursors of all involved catalytically active elements, were found to be promising in guiding the future efforts in tailoring an efficient catalyst for this system.

Unravelling the mechanisms of copper precipitation-induced strengthening in austenitic stainless steels: An atomistic approach

Copper addition in austenitic stainless steel is known to provide good high-temperature strength through precipitation strengthening. However, the mechanism of such strengthening and its overall contribution to strength in austenitic stainless steels have not been adequately investigated. The present work employs molecular dynamics (MD) simulation to investigate the interaction between an edge dislocation and copper precipitate in austenitic stainless steel. The mechanism controlling the strength was found to be trailing partial detachment for smaller precipitates up to a maximum radius of 3 nm, whereas leading partial detachment controls the strength for larger precipitate sizes, irrespective of the inter-precipitate spacing. Besides, modulus strengthening was identified as the primary strengthening contributor for the coherent Cu precipitate in the present alloy, which was subsequently aligned with the theoretical predictions by the existing Russell-Brown (R-B) model, adopting some modifications. The discrepancy between the simulation results and the original R-B model is attributed to the interaction between the two partial dislocations in presence of the precipitate. The modified R-B model was then used in combination with Thermo-calc and DICTRA predictions to estimate the strength of Cu-added austenitic stainless steel. However, the predictions overestimated the experimental data due to the model's inability to account for the random distribution of precipitates. To address this limitation, a subsequent discrete dislocation dynamics (DDD) simulation was conducted, incorporating a random distribution of Cu precipitates. Finally, the DDD simulation results demonstrated a good match with the experimental results, which can be further extended to other alloy systems as well.

Genesis of the Yi’nan Tongjing Gold–Copper Skarn Deposit, Luxi District, North China Craton: Evidence from Fluid Inclusions and H–O Isotopes

The Luxi district presents an exceptional research area for the investigation of the significant role played by magma exsolution fluids in the mineralization process of Au–Cu deposits. A particularly noteworthy occurrence within this region is the Yi’nan Tongjing Au–Cu skarn deposit, situated in the central-southern part of the Luxi district. This deposit primarily occurs in the contact zone between the early Cretaceous Tongjing complex and the Proterozoic to Cambrian sequences. The ore formation process observed in this deposit can be categorized into three distinct stages: (I) thermal metamorphism, (II) prograde alteration, and (III) retrograde alteration. The retrograde alteration stage is further divided into four sub-stages: late skarn (III-1), oxide (III-2), sulfide (III-3), and late quartz-calcite (III-4). It is primarily during the III-3 sub-stage that gold mineralization occurs. Petrographic analysis has identified three types of fluid inclusions (FIs) within garnet, quartz, and calcite grains. These include liquid-rich two-phase aqueous FIs, vapor-rich two-phase aqueous FIs, and halite-bearing multi-phase FIs. The homogenization temperatures of fluid inclusions from stages II, III-3, and III-4 range between 430–457 °C, 341–406 °C, and 166–215 °C (first to third quartiles), respectively. The garnet samples from stage II exhibit hydrogen and oxygen isotope compositions (δ18OH2O = 6.8‰ and δD = −73‰) that are indicative of a typical magma source. However, the hydrogen and oxygen isotopes of sub-stages III-1, III-2, and III-3 (δ18OH2O = 7.32‰ to 9.74‰; δD = −107‰ to −81.9‰) fall below the magma water box while the hydrogen and oxygen isotope values of III-4 (δ18OH2O = −5.3‰ to −0.9‰ and δD = −103.8‰ to −67‰) tend to move towards the meteoric water line. Furthermore, the ore-forming fluid displays characteristics of a mixture between the crustal and mantle fluids. The Tongjing complex occurred along a weakened fault zone, initiating a process of thermal metamorphism upon contact with the wall rock. This thermal metamorphism resulted in the formation of diverse assemblages, including hornfels, reaction skarns, and skarnoids. Subsequently, the upward movement of ore-forming fluids triggered exsolution which led to the establishment of a high-temperature, medium-salinity NaCl–H2O system with a single phase at depths ranging from 1–3 km. This marked the formation of the prograde alteration stage. Afterward, the ore-forming fluid underwent water–rock interactions and the admixture of meteoric water at a depth of 1–2 km. These processes facilitated phase separation, commonly referred to as boiling, resulting in the transformation of the ore-forming fluid into higher salinity fluids and lower-density gases. This evolutionary transition ultimately induced the precipitation and liberation of gold and copper from the fluid.

Mineral chemistry and apatite Sr isotope signatures record overprinting mineralization in the Duobaoshan porphyry Cu deposit, Heilongjiang Province, NE China

Porphyry copper deposits can be deformed by subsequent magmatic-tectonic-metamorphic evolution, resulting in the remobilization of pre-existing ores and the consequent overprinting mineralization. This process might potentially increase the ore grade and/or resource. We focus on the Duobaoshan porphyry Cu (Mo) deposit, two periods were identified in this study, i.e., porphyry period (including Stage 1: potassic alteration; 2: propylitic alteration, and 3: chlorite-sericite alteration and porphyry mineralization) and overprinting period (including Stage 4–1: ductile–brittle deformation; Stage 4–2 and Stage 4–3: overprinting mineralization). Metal sulfide veins occur along the schist in Stage 4–2 and Stage 4–3, features that differ from the typical porphyry mineralization of Stage 3 (veinlets, stockworks, and dissemination). Here, we present in situ Sr isotope data for apatite and compositions of chlorite, epidote, and apatite to reveal the source and nature of fluids and mechanism of precipitation during overprinting mineralization. The in situ 87Sr/86Sr ratios of apatite from Stages 3, which range from 0.7030 to 0.7046, are slightly higher than those observed in the Ordovician granodiorite. Meanwhile, the Sr isotope ratios for apatite from Stages 4–2 and 4–3 are 07033–0.7040 and 0.7013–0.7045 respectively. These ratios broadly consistent with those of the surrounding Ordovician granodiorite and basaltic andesite, suggesting that the ore-forming fluids for all these stages originated from magmatic sources. Chlorite in Stage 4–2 has a higher Mn, Co, Ni, Zn content compared to chlorite in Stage 3, 4–3, whereas epidote and apatite in Stage 4–2 have higher Ca, Sr, Pb content compared to those in Stage 3, 4–3, implying that the fluids in Stage 4–2 underwent strongly water–rock reactions and extracted metal elements from surrounding rocks. Copper was only detected in Stage 4–3 chlorite (15.13–500.20 ppm) and epidote (7.91–19.29 ppm), indicating a high concentration of copper in the fluid, and due to the pre-existing magnetite dissolution, chlorite, epidote, and apatite in Stage 4–3 exhibit high V and Fe relative to other stages. Fluid mixing likely occurred during Stage 3, leading to the precipitation of copper. Strong water-reaction in Stage 4–2 produce changes in fluid natures that facilitate sulfide deposition during this stage. While in Stage 4–3, copper precipitation is controlled by a combination of rising pH and changing sulfur content and valence. Our study highlights that in the Duobaoshan deposit, late magmatic-hydrothermal fluids remobilized pre-existing ore bodies, and the copper precipitation mechanisms differed during the main copper mineralization events.

The Casting and Hot Forging of Low-Carbon Copper-Bearing Steel and Its Substructural Characterization

The casting of metal alloys followed by hot forging is a widely used manufacturing technology to produce a homogeneous microstructure. The combination of mechanical and thermal energy envisages the microstructural properties of metal alloys. In the present investigation, a metal alloy of composition 0.05C-1.52Cu-1.51Mn (in weight %) was cast in an induction furnace using a zirconia crucible. The melt pool was monitored using optical emission spectroscopy (OES) to maintain the desired composition. The as-cast block was then subjected to forging under a pneumatic hammer of 0.5 t capacity so that any casting defects were eliminated. The as-cast block was reheated to a temperature of 1050 °C and held at that temperature for 6 h to homogenize, followed by hammering with a 50% strain using a pneumatic hammer. The microhardness was calculated using a Vickers microhardness testing apparatus. The microstructure characterization of the processed alloy was carried out using an optical microscope, electron backscattered diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDXA), and a transmission electron microscope (TEM). The sample for optical microscopy was cut using a diamond cutter grinding machine and surface polishing was carried out using emery paper. Further, mechanical polishing was performed to prepare the samples for EBSD using a TEGRAPOL polishing machine. The EBSD apparatus was operated at a 20 kV accelerating voltage, 25 mm from the gun, and with a 60 µ aperture size. HKL Technology Channel 5 Software was used for the post-processing of EBSD maps. The procedure of standard polishing for OES and TEM sample preparation was followed. Recrystallization envisages equiaxed grain formation in hot forging; hence, the strain-free grains were observed in the strained matrix. The lower distribution of recrystallized grains indicated that the driving force for recrystallization was not abundant enough to generate a fully recrystallized microstructure. The fractional distribution of the misorientation angle between 15 and 60° confirms the formation of grain boundaries (having a misorientation angle greater than 15°) and dislocations/subgrain/substructures (having a misorientation angle less than 15°). The fraction of misorientation angle distribution was higher between the angles 0.5 and 6.5°; afterwards, it decreased for higher angles. The substructure was observed in the vicinity of grain boundaries. The softening process released certain strains, but still, the dislocation was observed to be deposited mostly in the vicinity of grain boundaries and at the grain interior. The fine precipitates of the microalloying element copper were observed in the range of size in nanometers. However, the densities of these precipitates were limited and most of these precipitates were deposited at the grain interior. The microhardness of 210.8 Hv and mean subgrain size of 1.61 µ were observed the enhanced microhardness was due to the limited recrystallized grains and accumulation of dislocations/subgrain/substructures.

Gold recovery from electronic wastes using a solvent extraction/selective back-extraction strategy

ABSTRACT The present lab-scale investigation describes a simple and efficient approach to the selective solvent extraction and recovery of gold, and copper as a by-product, from Waste Printed Circuit Boards (WPCBs) of different brands of used computers. The process comprised of three steps; leaching of scraps in aqua regia, solvent extraction process under optimized conditions, and ultimately selective back-extraction. The analysis of leach solution by inductively coupled plasma revealed, in addition to gold (0.14 wt%), copper (40.0 wt%), tin (11.9 wt%), and Ni (2.3 wt%) were the other main metals in the WPCBs. A solvent extraction procedure using trioctylamine, as extractant, dissolved in kerosene was employed for the extraction of gold as its anionic chloride-complexes from the leach liquor. The parameters affecting this process including hydrochloric acid concentration, equilibrium time, extractant concentration, initial gold concentration in the sample solution, and the aqueous/organic volume ratio were optimized by means of the statistical technique response surface methodology (RSM). Under the optimized extraction conditions, 99.6% of gold and 23.4% of copper were transferred into the organic phase, while the extracted percentage of other metal ions were negligible. Selective back-extraction by the solution 0.1 M NaOH resulted in the selective precipitation of copper, while the raffinate contained just gold ions.

A Reevaluation of the Timing and Temperature of Copper and Molybdenum Precipitation in Porphyry Deposits

Abstract The timing and temperature at which copper-iron and molybdenum sulfide deposition occurs in porphyry deposits remain controversial. Petrologic estimates indicate that veins and wall-rock alteration zones containing copper-iron sulfides form in a wide temperature range from ~350° to 650°C. Most sulfides are hosted in potassium(K)-silicate–altered rock and quartz A veins or in early-halo alteration selvages formed above ~450°C. In contrast, cathodoluminescence (CL) imaging of A veins indicates that copper-iron sulfides are contained within a primary lucent (bright and gray)-CL quartz and are crosscut by microfractures filled with younger dull (dark and medium-gray)-CL quartz in direct contact with copper-iron sulfides. These observations have been interpreted as supporting late copper-iron sulfide introduction together with dull-CL quartz at moderate temperatures of ~300° to 450°C, based on fluid inclusion estimates. We provide new CL, QEMSCAN, and petrographic data and images of vein quartz as well as petrologic data of altered wall rock from Haquira East (Peru), Encuentro (Chile), and Batu Hijau (Indonesia) porphyry deposits, which were formed at conditions ranging from deep to shallow (~2–10 km). At all three deposits, dull-CL quartz in microfractures is ubiquitously observed crosscutting all generations of high-temperature lucent-CL quartz veins. Each lucent-CL vein type hosts distinct sulfide populations, crosscuts the others, and coexists in space within the copper and molybdenum ore zones. Within this ore zone, the dull-CL quartz only contains copper-iron sulfides where it transects old A veins and early halos, molybdenite where it transects young molybdenite-bearing quartz veins, and both copper-iron sulfides and molybdenite in younger B veins. Furthermore, where the dull-CL quartz crosscuts igneous or barren (deep) quartz veins, it typically lacks copper and molybdenum. Therefore, dull-CL quartz has no particular spatial or genetic affinity with copper-iron sulfides or molybdenite. We propose that copper was introduced and precipitated at high temperatures in stability with K-silicate alteration. In shallow porphyry deposits, most copper was introduced with lucent-CL quartz in A veins, likely formed via adiabatic decompression from magmatic lithostatic to hydrostatic conditions at ~450° to 600°C. In deep deposits, most copper is introduced with quartz-poor early halos, likely formed at a temperature range similar to that of A veins but during an early stage of retrograde silica solubility. The inferred timing and temperature of copper precipitation are consistent with available solubility experiments for copper-bearing solutions that suggest copper precipitation may start at a high temperature of ~600°C, and ~90% precipitates before it cools down to ~400°C. Much of the molybdenum is introduced and precipitated with discrete pulses of molybdenite-bearing quartz veins that crosscut and postdate copper-bearing A veins and early halos and, to a lesser degree, with B veins that may carry both copper and molybdenum. Whereas molybdenite-bearing and barren (deep) quartz veins form at relatively high temperatures of ~550° to 650°C, copper-molybdenum–bearing B veins likely form at lower temperatures near ~500°C. Copper precipitation and local copper remobilization from older veins and halos continued during the formation of copper-iron sulfide veinlets, named C veins, and during the precipitation of dull-CL quartz following K-silicate alteration. C veins and even younger pyrite-rich D veins may have chlorite or sericite selvages and are composed of dull-CL quartz that formed at ~450° and 300° to 450°C, respectively. Microfractures form through all lucent-CL quartz veins because of the thermal contraction of high-temperature quartz at the onset of sustained cooling after K-silicate alteration has ceased. The fluid that migrated through these microfractures was initially in retrograde silica solubility, which causes dissolution and corrosion of the older lucent-CL quartz. The formation of C veins may overlap in time with the initial stage. At a later stage and temperatures below &amp;lt;450°C, the fluid precipitates dull-CL quartz in microfractures and dissolution zones within older lucent-CL quartz. In copper-iron sulfide-bearing A and B veins and molybdenite-bearing quartz veins, corroded lucent-CL quartz and the younger dull-CL quartz infill can often be observed in contact with older sulfides because quartz sulfide grain boundaries are preexisting discontinuities, and they are preferentially opened during volume contraction. Collectively, these observations and estimates are consistent with silicate phase petrology and numerous observations that most copper-iron sulfides precipitate in K-silicate alteration zones or in early halos with K-feldspar-muscovite-biotite assemblages.

Study on Selective Leaching of Copper and Simultaneous Precipitation of Iron in Polymetallic Complex Chalcopyrite by Hydrothermal Leaching Under Oxygen Pressure

Study on Selective Leaching of Copper and Simultaneous Precipitation of Iron in Polymetallic Complex Chalcopyrite by Hydrothermal Leaching Under Oxygen Pressure