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Due to the scarcity of water in many parts of the world, wastewater generated by hydrometallurgical processes has been recognized as a valuable resource for recovery or reuse. A method for reusing hydrometallurgical raffinate in the leaching of low-grade oxide copper ore in a counter-current leaching process was evaluated. In the first stage of the investigation, the influential factors on copper leaching, such as the amount of acid consumed (200–400 g/kg of ore), the initial iron concentration of the raffinate (5–25 g/L), the liquid-to-solid ratio (2–10 mL/g), and the duration of the leaching process (15–75 min), were examined using response surface methodology coupled with central composite design. Two responses, copper recovery and final copper concentration, were selected to determine the optimal conditions for the leaching process. Based on the statistical model, it was found that using 325 g/kg of ore of consumed acid, an initial iron concentration of 10 g/L, a liquid-to-solid ratio of 4 mL/g, and a leaching time of 60 min would result in higher values for both responses. Confirmation runs were conducted to validate the selected conditions and the suitability of the statistical model. Additionally, compositional and morphological characterization of samples before and after the leaching process was conducted using field diffusion scanning electron microscopy and X-ray diffraction analysis, which showed the dissolution of compounds such as tenorite and cuprite. In the second stage, a two-unit counter-current leaching system was adopted, as hydrometallurgical processes are usually carried out in multiple stages on an industrial scale. This leaching system was designed to maximize copper dissolution by considering the information obtained from the response surface methodology. The use of this leaching system increased the overall leaching efficiency by up to 80%. By characterizing the solid samples, it was found that the copper extraction percentage in a counter-current leaching system could be increased by simultaneously precipitating iron-bearing compounds. [ABSTRACT FROM AUTHOR]

Availability of safe drinking water is a major concern in many parts of the world. While many filtration units operating on various principles are available to combat this, most require electricity, which may not be consistently available in such areas. In the present study, we have designed and demonstrated a water disinfection system that can operate purely on gravity, without any electricity. For this, a potassium hydroxide modified copper‐impregnated activated carbon (KOH‐Cu‐AC) hybrid was used as a filter medium for disinfection, because it is less expensive, with performance comparable to previously reported hybrids containing silver. To maintain a constant water flow rate under gravity, during disinfection, a Mariotte bottle was used as the reservoir of the contaminated water. Using this and a constant head between the bottle and the treated water exit point, the required water‐filter contact time of 25 min (for decontamination) is maintained in the filter column, regardless of tank‐fill level. The demonstrated lab‐scale system can perform disinfection of simulated contaminated water (with an initial concentration of 104 CFU mL−1Escherichia coli), for at least 6 h, with a flow rate of 150 mL h−1. The disinfection performance from the gravity‐based filter was further validated with the conventional pump‐driven filter, used for continuous disinfection of drinking water. Equivalence of results between pump‐ and gravity‐driven operations helps us to eliminate the need for power, without any compromise in disinfection efficacy. Finally, copper concentration from treated water (106 ppb at steady state) remains very well within the safe limit (1000 ppb as per USEPA guideline). Hence, the lab‐scale design of gravity‐based packed bed filter will be useful for domestic and community‐based supply of safe drinking water in resource‐constrained areas, because it eliminated electricity requirement of conventional power‐driven systems. Practitioner Points: Cost‐effective KOH‐Cu‐AC hybrid is developed as a disinfection material.Mariotte bottle used for maintaining constant disinfected water flow rate works without any electrical power supply.This system can be used for getting on‐spot, continuous disinfected water supply.The concentration of copper in the treated water is well within the safety limit.It can be applicable in rural and remote areas (no electric power source) as well as natural calamity‐affected areas. [ABSTRACT FROM AUTHOR]

Oxidative leaching, as a basic step of the hydrometallurgical process of pure copper production from chalcopyrite, is a slow process in which mineral acids with strong oxidants addition are usually used as a leaching medium. It was found experimentally that the copper leaching from chalcopyrite in the H2SO4–H2O2–H2O system, in the presence of isopropanol (IPA) and under other conditions (H2O2 concentration, rate of mixing and temperature), takes place with satisfactory rate and efficiency. To quantify how much the change of these crucial variables affects the rate of the process, experimentally obtained kinetic curves (conversion over time) were analyzed using a Shrinking Core Model (SCM). The determined values of the copper leaching rate constants (kobs) confirmed the positive influence of increasing IPA and H2O2 concentrations as well as the temperature on the kinetics and efficiency of the leaching. The kinetic studies were also supported by using X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, scanning electron microscopy (SEM), and adsorption measurements. The positive influence of IPA was explained by its stabilizing role for iron compounds (hematite, magnetite, and pyrite), which are catalysts during the Cu dissolution, as well as H2O2 protection from decomposition during free radical reactions. Finally, the optimal conditions for efficient leaching, the rate-limiting step as well as the mechanism suggestion of the copper dissolution, were given. [ABSTRACT FROM AUTHOR]

Nowadays, deep eutectic solvents (DESs) are seen as environmentally friendly alternatives with the potential to replace traditional solvents used in hydrometallurgical processes. Although DESs have been successfully applied in the recovery of metals from secondary sources, there is still innovative potential regarding DESs as green leaching agents applied in the recovery of metals from primary sources like polysulfide ores. This study aimed to evaluate the characteristics of DESs as solvents for some of the main metals present in typical polymetallic concentrates, like Cu, Fe, Pb, and Zn. Thus, three DESs based on choline chloride (ChCl) were prepared: 1:2 ChCl-urea (also known as reline), 1:2 ChCl-ethylene glycol (also known as ethaline), and 1:2 ChCl-glycerol (also known as glyceline). Then, dissolution tests at 30 °C were carried out with these DESs and different metal- (Cu, Fe, Pb, and Zn) bearing compounds (sulfates, oxides, and sulfides). According to the dissolution tests, it was found that the solubility of the studied metals (expressed as g of metal per Kg of DES) was dictated by the bearing species, reaching the dissolution of the metals from sulfates with values as high as two orders of magnitude higher than the metal solubility values for metal oxides and sulfides. [ABSTRACT FROM AUTHOR]

Mineralogy and chemical composition are the main indicators for selecting operational parameters for copper leaching from mineral resources and smelting furnace dust. The main goal of this research is to evaluate the dust composition of chalcopyrite concentrate smelting furnaces to improve copper leaching efficiency. In this regard, for four months, samples were taken daily from the dust of the smelting furnaces of Sarcheshme copper complex. Using X-ray diffraction analysis, X-ray fluorescence spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and reflective light microscopy, the composition of the samples was determined and leaching tests were designed and implemented to determine the main operational parameters. The results of this study showed that the grain size distribution of the samples did not change significantly during the sampling period, but the amount of some elements such as arsenic was varried and fluctuated between 0.17 and 3.90%. The changes of copper and iron were also about 2%. The results of leaching tests of flash furnace dust showed that the solid percentage, acid concentration and temperature are the most important operating parameters. Under the optimal operating conditions, about 65% of copper is dissolved without the use of an oxidizer within a maximum of 60 minutes. By using a two-stage electrochemical process, the conditions for extracting more than 95% of copper from flash furnace dust was provided. [ABSTRACT FROM AUTHOR]

In this study, SDS is used to enhance the sulfuric acid leaching of chalcopyrite in aqueous and isopropanol media. The presence of SDS increased copper extraction into the solution in both solvents. However, it was the "isopropanol–sulfuric acid–SDS" system that proved to be particularly effective for copper recovery from chalcopyrite. The positive effect of SDS can be attributed to the reduction in the solution's surface tension and the enhancement of mineral wetting. Additionally, the presence of SDS as a surfactant induces changes in the adsorption patterns of formed sulfur species on the mineral surface. SDS competes with sulfur for occupancy on the surface binding sites. This competitive interaction has the potential to diminish the formation of a substantial sulfur layer on the mineral surface. Under optimal conditions (isopropanol media, 2 M H2SO4, 65 °C, 120 min, 0.6 g/L SDS), copper recovery into the solution was 83%, and this is a considerable achievement for chalcopyrite leaching at ambient pressure in the absence of strong oxidizers. [ABSTRACT FROM AUTHOR]

The leaching of Cu in ammoniacal solutions has proven an efficient method to recover Cu from waste printed circuit boards (WPCBs) that has used by many researchers over the last two decades. This study investigates the feasibility of a counter-current leaching circuit that would be coupled with an electrowinning (EW) cell. To accomplish this objective, the paper is divided into three parts. In Part 1, a leaching kinetic framework is developed from a set of experiments that were designed and conducted using end-of-life waste RAM chips as feed sources and Cu(II)-ammoniacal solution as the lixiviant. Various processing parameters, such as particle size, stirring rates, initial Cu(II) concentrations, and temperatures, were evaluated for their effects on the Cu recovery and the leaching rate. It was found that the particle size and initial Cu(II) concentration were the two most important factors in Cu leaching. Using a 1.2 mm particle size diameter and 40 g/L of initial Cu(II) concentration, a maximum Cu recovery of 96% was achieved. The Zhuravlev changing-concentration model was selected to develop the empirically fitted kinetic coefficients. In Part 2, kinetic data were adapted into a leaching function suitable for continuously stirred tank reactors. This was achieved via using the coefficients from the Zhuravlev model and adapting them to the Jander constant concentration model for use in the counter-current circuit model. Part 3 details the development of a counter-current circuit model based on the relevant kinetic model, and the circuit performance was modeled to provide a tool that would allow the exploration of maximum copper recovery whilst minimizing the Cu(II) reporting to electrowinning. A 4-stage counter-current circuit was modeled incorporating a feed of 35 g/L of Cu(II), achieving a 4.12 g/L Cu(II) output with 93% copper recovery. [ABSTRACT FROM AUTHOR]

This paper provides an overview of hydrometallurgical copper extraction studies in which liquid extraction technology has been used with four copper deposits of different compositions. The sulfuric acid consumption rate and copper extraction efficiency, which are dependent on the initial content and forms of calcium compounds and other impurities in ore samples, were calculated, and the results are presented herein. It was established that during the leaching process, silicate compounds of alkaline earth metals, in addition to calcium and magnesium carbonate compounds, would affect the levels of sulfuric acid consumption, thereby actively lowering the acidity of the environment. Moreover, these compounds could partially sorb copper ions from sulfuric acid leaching solutions. Thus, the analysis of waste ore samples showed that residual copper is mainly contained in the form of complex silicate complexes. The presence of divalent iron compounds in the composition from one of the deposits also allowed us to perform a biochemical leaching experiment with preliminary oxidation using an Acidithiobacillus ferrooxidans bacterial culture adapted to the ore composition. The use of this biochemical method in the copper leaching process resulted in a significant reduction in sulfuric acid consumption, by 40%, and a copper recovery rate of 87.2%. [ABSTRACT FROM AUTHOR]

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Oxidative leaching, as a basic step of the hydrometallurgical process of pure copper production from chalcopyrite, is a slow process in which mineral acids with strong oxidants addition are usually used as a leaching medium. It was found experimentally that the copper leaching from chalcopyrite in the H2SO4–H2O2–H2O system, in the presence of isopropanol (IPA) and under other conditions (H2O2 concentration, rate of mixing and temperature), takes place with satisfactory rate and efficiency. To quantify how much the change of these crucial variables affects the rate of the process, experimentally obtained kinetic curves (conversion over time) were analyzed using a Shrinking Core Model (SCM). The determined values of the copper leaching rate constants (kobs) confirmed the positive influence of increasing IPA and H2O2 concentrations as well as the temperature on the kinetics and efficiency of the leaching. The kinetic studies were also supported by using X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, scanning electron microscopy (SEM), and adsorption measurements. The positive influence of IPA was explained by its stabilizing role for iron compounds (hematite, magnetite, and pyrite), which are catalysts during the Cu dissolution, as well as H2O2 protection from decomposition during free radical reactions. Finally, the optimal conditions for efficient leaching, the rate-limiting step as well as the mechanism suggestion of the copper dissolution, were given.

Nowadays, deep eutectic solvents (DESs) are seen as environmentally friendly alternatives with the potential to replace traditional solvents used in hydrometallurgical processes. Although DESs have been successfully applied in the recovery of metals from secondary sources, there is still innovative potential regarding DESs as green leaching agents applied in the recovery of metals from primary sources like polysulfide ores. This study aimed to evaluate the characteristics of DESs as solvents for some of the main metals present in typical polymetallic concentrates, like Cu, Fe, Pb, and Zn. Thus, three DESs based on choline chloride (ChCl) were prepared: 1:2 ChCl-urea (also known as reline), 1:2 ChCl-ethylene glycol (also known as ethaline), and 1:2 ChCl-glycerol (also known as glyceline). Then, dissolution tests at 30 °C were carried out with these DESs and different metal- (Cu, Fe, Pb, and Zn) bearing compounds (sulfates, oxides, and sulfides). According to the dissolution tests, it was found that the solubility of the studied metals (expressed as g of metal per Kg of DES) was dictated by the bearing species, reaching the dissolution of the metals from sulfates with values as high as two orders of magnitude higher than the metal solubility values for metal oxides and sulfides.

In this study, SDS is used to enhance the sulfuric acid leaching of chalcopyrite in aqueous and isopropanol media. The presence of SDS increased copper extraction into the solution in both solvents. However, it was the “isopropanol–sulfuric acid–SDS” system that proved to be particularly effective for copper recovery from chalcopyrite. The positive effect of SDS can be attributed to the reduction in the solution’s surface tension and the enhancement of mineral wetting. Additionally, the presence of SDS as a surfactant induces changes in the adsorption patterns of formed sulfur species on the mineral surface. SDS competes with sulfur for occupancy on the surface binding sites. This competitive interaction has the potential to diminish the formation of a substantial sulfur layer on the mineral surface. Under optimal conditions (isopropanol media, 2 M H2SO4, 65 °C, 120 min, 0.6 g/L SDS), copper recovery into the solution was 83%, and this is a considerable achievement for chalcopyrite leaching at ambient pressure in the absence of strong oxidizers.

The leaching of Cu in ammoniacal solutions has proven an efficient method to recover Cu from waste printed circuit boards (WPCBs) that has used by many researchers over the last two decades. This study investigates the feasibility of a counter-current leaching circuit that would be coupled with an electrowinning (EW) cell. To accomplish this objective, the paper is divided into three parts. In Part 1, a leaching kinetic framework is developed from a set of experiments that were designed and conducted using end-of-life waste RAM chips as feed sources and Cu(II)-ammoniacal solution as the lixiviant. Various processing parameters, such as particle size, stirring rates, initial Cu(II) concentrations, and temperatures, were evaluated for their effects on the Cu recovery and the leaching rate. It was found that the particle size and initial Cu(II) concentration were the two most important factors in Cu leaching. Using a 1.2 mm particle size diameter and 40 g/L of initial Cu(II) concentration, a maximum Cu recovery of 96% was achieved. The Zhuravlev changing-concentration model was selected to develop the empirically fitted kinetic coefficients. In Part 2, kinetic data were adapted into a leaching function suitable for continuously stirred tank reactors. This was achieved via using the coefficients from the Zhuravlev model and adapting them to the Jander constant concentration model for use in the counter-current circuit model. Part 3 details the development of a counter-current circuit model based on the relevant kinetic model, and the circuit performance was modeled to provide a tool that would allow the exploration of maximum copper recovery whilst minimizing the Cu(II) reporting to electrowinning. A 4-stage counter-current circuit was modeled incorporating a feed of 35 g/L of Cu(II), achieving a 4.12 g/L Cu(II) output with 93% copper recovery.

[Display omitted] • The series of leaching cells was beneficial utilization of Cl 2. • Leaching time and HCl concentration had great effects on dissolution of Cu. • Double intake pipes and bubble stone improved the leaching efficiency of Cu. • Reduction of Cl 2 gas bubbles improved the leaching kinetics and shorter time. This paper investigated the improved leaching of Cu, Sn, Pb, Zn, and Al from waste printed circuit boards (WPCBs) by electro-generated Cl 2 in HCl solution through multiple leaching cells in series, double intake pipes, and bubble stone for leaching. The leaching agents in the leaching cell include Cl 2 (aq), HCl, HClO, and Cl 3 -. The leaching rate and leaching speed of Zn, Sn, Al, and Pb exceeded that of Cu. Leaching time and HCl concentration have a strong impact on the dissolution of Cu, whereas the effect of the electrolytic current and the leaching temperature is comparably weak. The series of leaching cells improved the effective utilization of Cl 2 and increased the treatment capacity of the WPCBs. Bubble stones significantly enhanced the efficiency and rate of leaching. Reduction of the size of the Cl 2 gas bubbles improved the leaching kinetics. The leaching rate of Cu reached 87.22%, whereas the leaching rate of Zn, Sn, Al, and Pb exceeded 90% after 100 min. Our experimental data provide a reference for electrolytic leaching recovery of metals from WPCBs, and our method improves the metal leaching and electrolytic efficiency in practice. [ABSTRACT FROM AUTHOR]

This paper provides an overview of hydrometallurgical copper extraction studies in which liquid extraction technology has been used with four copper deposits of different compositions. The sulfuric acid consumption rate and copper extraction efficiency, which are dependent on the initial content and forms of calcium compounds and other impurities in ore samples, were calculated, and the results are presented herein. It was established that during the leaching process, silicate compounds of alkaline earth metals, in addition to calcium and magnesium carbonate compounds, would affect the levels of sulfuric acid consumption, thereby actively lowering the acidity of the environment. Moreover, these compounds could partially sorb copper ions from sulfuric acid leaching solutions. Thus, the analysis of waste ore samples showed that residual copper is mainly contained in the form of complex silicate complexes. The presence of divalent iron compounds in the composition from one of the deposits also allowed us to perform a biochemical leaching experiment with preliminary oxidation using an Acidithiobacillus ferrooxidans bacterial culture adapted to the ore composition. The use of this biochemical method in the copper leaching process resulted in a significant reduction in sulfuric acid consumption, by 40%, and a copper recovery rate of 87.2%.

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. [ABSTRACT FROM AUTHOR]

Flash furnace dusts generated in copper pyrometallurgy are habitually recirculated to the furnace for copper recovery and as a cold burden material. However, it is necessary bled the dusts in order to reduce the amount of impurities to be recycled to the furnace. The most important processes for the treatment of Flash furnace dusts applied at the industrial scale are hydrometallurgical and mainly involve sulfuric acid. The objective of this work was to study the leaching of Flash furnace dusts generated in the Huelva, Spain, plant of Atlantic Copper using sulfuric acid. The work compares a leaching process developed in two steps, (first step with water, followed by leaching with sulfuric acid) to obtain a more selective leaching, or in a single step also with sulfuric acid, which decreases the operations number. A weak acid bleed (wab), from the same plant, was used as a source of sulfuric acid. After leaching, the concentration of sulfates and the acidity were reduced by gypsum precipitation. The liquids generated in this way are suitable for subsequent treatments of arsenic-iron precipitation and copper recovery by electrolysis. [ABSTRACT FROM AUTHOR]

Copper smelters produce solid waste streams that pose potential pollution problems because of the dust and metal content. Dust from flash and electric furnace smelters is normally recycled to the smelting process, but this decreases the capacity for concentrate feed, and increases impurities and carryovers in the dust with time. The purpose of this study was to test an acid bioleaching process for recovering copper from a sample of smelter dust. The dust sample contained delafossite, chalcocyanite, and chalcopyrite as the main Cu-minerals. Smelter dust (10% pulp) in acid leach solution was subjected to three microbial cultures in a sequence of 35°C, 50°C, and 70°C incremental temperatures for 2 days each. Up to 83% copper dissolution from the dust was achieved by the combined action of the three-phase bioleaching and chemical leaching over the contact time of 6 days. Chemical acid demand at 70°C solubilized 68% Cu from smelter dust within 2 h, attributed to chalcocyanite dissolution in the dust. The monovalent copper minerals chalcopyrite and delafossite were more recalcitrant than the sulfate phase chalcocyanite. A 16-day bioleaching experiment at 35°C and 50°C yielded copper recoveries, which were comparable to those obtained in the three-phase bioleaching. It was concluded that further increases in copper yields from smelter dust require extended contact time ideally at the extreme thermophilic temperature range and stirred bioreactor conditions to control key parameters. [ABSTRACT FROM AUTHOR]

Present paper investigates the dissolution behavior of copper from chalcopyrite concentrate sample using cupric chloride solution in detail. Response surface modeling (RSM) in combination with d-optimal design (DOD) was utilized for modeling and optimizing the cupric chloride leaching process. At first, a quadratic polynomial model was developed for the relationship between the recovery of copper and influential factors. The predictions indicated an excellent agreement with the experimental data (with R2 of 0.9399). Then, the effects of main factors including pH (1-4), liquid/solid ratio (2-7 mL/g), temperature (70-90 °C), CuCl2 concentration (6-35 g/L), and leaching time (0.5-16) were determined. The findings demonstrated that the temperature and CuCl2 concentration were the most effective factors on the dissolution rate of copper from chalcopyrite sample, while liquid/solid ratio had the lowest impact. The recovery of copper increased linearly with an increment in the liquid/solid ratio and the decrease in the pulp pH. Additionally, the recovery enhanced by increasing the temperature and CuCl2 concentration owing the generation of Cu–Cl complexes species and reached a plateau point and then almost remained unchanged. Meanwhile, it was found out that the recovery of copper was independent of the interaction between factors. Moreover, the optimization of leaching process was carried out by Design Expert (version 7) software and desirability function method and the highest recovery of copper was found to be about 86.1% at a pH of ~1.4, temperature of 89 °C, liquid/solid ratio of 6.8 mL/g, CuCl2 concentration of 21.79 g/L and leaching time of ~8 h.

Currently, the generation of electrical and electronic wastes is growing fast, thereby the reduction of the environmental impacts generated by its inadequate disposal is an ongoing challenge. In this study, a research on the use of monosodium glutamate for copper leaching, with emphasis on the thermodynamics and oxidant characteristics, is presented. Copper dissolution was conducted following a hydrometallurgical route, using monosodium glutamate in alkaline solutions. The effect of oxidizing agents such as hydrogen peroxide (H2O2) and potassium permanganate (KMnO4), and the efficiency of copper leaching with glutamate compared with glycine have been studied. Results, obtained at room temperature, showed 92% recovery of copper using 0.03 M hydrogen peroxide, 0.5 M monosodium glutamate at a pH of 9.44. This novel method would allow the extraction of copper from WEEE at low temperature, using an environmentally friendly leaching amino acid for the recovery of copper from electronic waste.

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.

The parameters of the continuous technological process of leaching copper from fine copper waste using nitric acid as an oxidizer are studied. Optimal conditions for a continuous leaching process were established, in which solutions with a mass concentration of copper ions greater than 25 g/dm3 were obtained.

A method to develop thermo-kinetic (TK) diagrams for the Cu−H2O−acetate and Cu−H2O systems is described. Conventional Eh-pH diagrams, also known as Pourbaix diagrams, are developed based on the thermodynamic stability of component species, typically in aqueous media. TK diagrams are an improvement on Eh-pH diagrams as they also describe the kinetics of electrochemical processes. These diagrams are developed by using data from linear scan voltammetry of Cu rotating disk electrodes exposed to aqueous media of different pH. By applying the same procedure, the TK diagrams can be developed for other metals or mineral systems exposed to aqueous media containing ligands. To ensure reproducibility and reconstruction of the TK diagrams for other metal/mineral/electrolyte systems, some important experimental considerations are highlighted in this study. These TK diagrams are useful to evaluate the corrosion of metals, the leaching performance of minerals and to predict the suitable conditions for metal recycling processes.Briefly, this article explains: • Important experimental considerations that could affect the kinetics of electrochemical processes. • A method to construct TK diagrams with examples of the Cu−H2O−acetate and Cu−H2O systems. • With overlaid Eh-pH diagrams, TK diagrams explain both the thermodynamic stability of component species and the kinetics of the electrochemical processes.

The self-assembly of amphiphilic molecules onto solid substrates can result both in the formation of monolayers and multilayers. However, on oxidized and non-oxidized copper (Cu), only monolayer formation was reported for phosphonic acids possessing one phosphate head group. Here, the adsorption of octadecylphosphonic acid (ODPA) on Cu substrates through a self-assembly process was investigated with the initial hypothesis of monolayer formation. The relative amount of ODPA adsorbed on a Cu substrate was determined by infrared reflection/absorption spectroscopy (IRRAS) and by atomic force microscopy (AFM) investigations before and after ODPA deposition. X-ray photoelectron spectroscopy (XPS) with sputtering was used to characterize the nature of the layers. The results show that the thickness of the ODPA layer increased with deposition time, and after 1 h a multilayer film with a thickness of some tens of nm was formed. The film was robust and required long-time sonication for removal. The origin of the film robustness was attributed to the release of Cu ions, resulting in the formation of Cu-ODPA complexes with Cu ions in the form of Cu(I). Preadsorbing a monolayer of octadecylthiol (ODT) onto the Cu resulted in no ODPA adsorption, since the release of Cu(I) ions was abolished. [ABSTRACT FROM AUTHOR]

As pH of leaching medium is an important factor in the leaching of wood preservative components, its effects on leaching should be quantified to ensure environmentally safe use of treated wood. In this study, the effects of pH on leaching of copper from wood treated with copper amine-based preservatives [alkaline copper quat (ACQ)-2, bis-(N-cyclohexyldiazeniumdioxy)-copper (CuHDO)-3, and copper azole (CUAZ)-3] were evaluated in comparison with wood treated with chromated copper arsenate (CCA)-3. Radiata pine sapwood blocks treated with these preservatives were leached at five pH levels (3.0, 3.5, 4.0, 4.5, and 6.5). The leached blocks were subjected to laboratory-scale decay tests using two brown-rot fungi. The blocks treated with copper amine-based preservatives leached significant amounts of copper at pH levels below 4.0. At all pH levels, the CuHDO-3-treated samples generally leached the most copper, followed by the samples treated with ACQ-2, CUAZ-3, and CCA-3. When the treated blocks were leached at pH 3.0, the degradation of hemicelluloses, which can chemically adsorb copper, was confirmed through Fourier transform infrared attenuated total reflectance (FTIR-ATR) analysis. Moreover, X-ray photoelectron spectroscopy (XPS) analysis indicated that the ratio of precipitates of the remaining copper in the treated wood severely decreased after leaching at pH levels below 4.0. Subsequent reduction in the biological effectiveness of wood treated with copper amine-based preservatives was not hardly observed after leaching at pH levels 4.0 or above. These results indicate that copper loss at pH levels 4.0 or above is not great enough to cause public concern about environmental problems and reduction of biological efficacy in practical applications. [ABSTRACT FROM AUTHOR]

The present paper is a detailed investigation of the dissolution behavior of copper from the chalcopyrite concentrate sample using a cupric chloride solution. Response surface modeling (RSM) in combination with d-optimal design (DOD) was utilized for modeling and optimizing the cupric chloride leaching process. Initially, a quadratic polynomial model was developed for the relationship between the recovery of copper and influential factors. The predictions indicated an excellent agreement with the experimental data (with R2 of 0.9399). Then, the effect of main factors including pH (1-4), liquid/solid ratio (2-7 mL/g), temperature (70-90 °C), CuCl2 concentration (6-35 g/L), and leaching time (0.5-16) were determined. The findings demonstrated that the temperature and CuCl2 concentration were the most effective factors on the dissolution rate of copper from chalcopyrite sample, while the liquid/solid ratio had the lowest impact. The recovery of copper increased linearly with an increment in the liquid/solid ratio and the decrease in the pulp pH. Additionally, the recovery enhanced by increasing the temperature and CuCl2 concentration owing to generation of Cu-Cl complexes species and reached a plateau point and then almost remained unchanged. Meanwhile, it was observed that the recovery of copper was independent of the interaction between factors. Moreover, the optimization of leaching process was carried out by Design Expert (version 7) software and desirability function method and the highest recovery of copper was found to be about 86.1% at a pH of ~1.4, temperature of 89 °C, liquid/solid ratio of 6.8 mL/g, CuCl2 concentration of 21.79 g/L and leaching time of ~8 h. [ABSTRACT FROM AUTHOR]

In order to study the kinetics of copper leaching from pyrite cinder containing 0. 87%Cu sulfuric acid slag alter being roasted at high temperature, the properties of ore were analyzed by X-ray diffraction and other methods. The effects of ore particle size，initial acidity，liquid-so lid ratio，stirring rate，leaching temperature and leaching time on copper leaching in sulfuric acid slag samples were studied experimentally. The unreacted shrinking nucleus model is used to analyze the kinetics of the sulfuric acid slag leaching process. The results show that all factors have a great influence on the leaching rate of copper leaching of sulfuric acid slag; based on the leaching process controf model，leaching kinetic equation，leaching reaction appearance in terms of activation energy，the main controf step of determining the slag leaching process is internal diffusion reaction controfs, and the apparent activation energy of the leaching reaction is E, --19. 96 kJ/mof. [ABSTRACT FROM AUTHOR]

• Efficacy of rubberwood impregnated with MCA was evaluated and compared with CCA. • Treated rubberwood exhibited requisite amount of preservative retention. • Treated wood showed sharp increase followed by gradual decrease in copper leaching. • Except MOR, no deleterious effect was observed on hardness of treated rubberwood. • SEM showed small size copper particles in the pits and parenchyma of treated wood. • Treated wood exhibited lower weight loss compared to control after exposure to fungi. • MCA treatments may be recommended in enhancing durability of perishable timbers. This study objective was to investigate the biological efficacy of a commercial dispersion of micronized copper azole (MCA) on plantation grown rubberwood. MCA is a formulation containing micronized copper carbonates and azole, an organic co-biocide. The impact of MCA pressure treatments with various concentrations of the active ingredients and the treatment durations on retentions, leaching rate, mechanical properties and biological performance against brown and white rots were evaluated. Biological performance of MCA treated rubberwood at minimum retention of 2.8 ± 0.3 kg/m3 was found to be comparable to that of chromated copper arsenate (CCA) treatment at 15.1 ± 2.3 kg/m3. Field tests are being conducted to confirm the laboratory findings. [ABSTRACT FROM AUTHOR]

Chalcopyrite leaching in acidic ferric sulfate media at ambient temperature exhibits slow kinetics due to the formation of passivation layers on chalcopyrite surfaces. In this study, we investigated the use of potassium iodide to assist chalcopyrite leaching and proposed mechanisms by which iodide enhanced the leaching efficiency. The effect of ferric concentration, temperature and iodide concentration on chalcopyrite leaching was studied by factorial experimental design and statistical analysis of data using the analysis of variance (ANOVA) method. The addition of 0.5 g/L of potassium iodide to the leaching media containing Fe(III) resulted in the production of I 2 and led to an increase of copper extraction by 47% at 50 °C. Controlled potential experiments highlighted an optimal potential window for leaching at 700–800 mV, thus suggesting that tri-iodide might play a significant role in leaching enhancement. Mineral liberation analysis (MLA) highlighted that elemental sulfur was the surface product generated from the oxidation of chalcopyrite. The rate parameters in the presence of KI were significantly higher, especially at lower temperature, and consistent with those observed for the H 2 SO 4 -I 2 leaching media. The addition of potassium iodide into the leaching media led to a decrease of activation energy from 81.4 to 33.8 kJ/mol. • Copper was efficiently extracted from chalcopyrite in H 2 SO 4 -Fe 2 (SO 4) 3 -KI media. • Sulfur accumulated on chalcopyrite but, with KI, Cu extraction increased up to 87%. • The leaching kinetics was enhanced upon addition of KI and its oxidation to I 2. • Kinetics was described by the ash-diffusion expression of the shrinking core model. • The leaching activation energy decreased from 81 to 33 kJ/mol with 0.5 g/L of KI. [ABSTRACT FROM AUTHOR]

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Flash furnace electrostatic precipitator dust (FF-ESP dust) is a recycle stream in some primary copper production facilities. This dust contains high amounts of copper. In some cases, the FF-ESP dust contains elevated levels of bismuth and arsenic, both of which cause problems during the electrorefining stages of copper production. Because of this, methods for separation of copper from bismuth and arsenic in FF-ESP dust are necessary. Hydrometallurgical leaching using a number of lixiviants, including sulfuric acid, sulfurous acid, sodium hydroxide, and water, were explored. Pourbaix diagrams of copper, bismuth, and arsenic were used to determine sets of conditions which would thermodynamically separate copper from bismuth and arsenic. The data indicate that water provides the best overall separation between copper and both bismuth and arsenic. Sodium hydroxide provided a separation between copper and arsenic. Sulfurous acid provided a separation between copper and bismuth. Sulfuric acid did not provide any separations between copper and bismuth or copper and arsenic.

Southern pine (Pinus sp.) wood cubes were treated with ACQ solutions with wax modification and post-treated at 70 °C for 10 h with hot air circulation. The effects of wax concentrations in ACQ-treated southern pine on its dimensional stability and copper leaching performance were investigated. The ACQ/wax-treated wood exhibited improved water resistance during the water soak process. The testing of swelling and shrinkage performance of the treated wood showed that samples with a higher percentage of wax had higher resistance to water swelling and shrinkage. The samples with a lower percentage of wax addition had only a slight effect on the moisture swelling and shrinkage resistance. As a result, copper leaching from ACQ/wax-treated wood with a 2% wax concentration was reduced to a lower level compared to ACQ-treated wood. When the proportion of wax in ACQ preservative was less than 1%, a higher percentage of copper was leached from treated wood.

The article presents data from theoretical and experimental studies related to the search for a solution to an urgent geotechnological problem - selective mining of standard quality ore, substandard and diluted ores, taking into account the peculiarities of their processing by heap leaching. For complex-structural large-scale ore deposits of the stockwork morphological-structural type, multilevel heterogeneity is typical. The morphology and structure of the objects of direct extraction - ore bodies within the production blocks - vary significantly. The expediency of selective mining and separate heap leaching (or heap oxidation and leaching) of gold and copper from conditioned ores of various geological and technological types and grades is justified. In addition, it is advisable to selectively extract and separately process by heap leaching or flux in a controlled manner before it off-balance and diluted ores, as well as mineralized overburden and tailings of high-grade ores.

This study includes solvent extraction and electrowinning of copper from leaching process. The Taguchi method was used to determine the optimum conditions for solvent extraction process of copper ore in sulfuric acid solution. The experimental parameters of solvent extraction were: Extractant mass of sodium diethyldithiocarbamate (SDDT), agitation time, and pH value. While, the electrowinning parameters were constant at 25°C temperature, reaction voltage of 2 V, 200 A/dm2 current density, and 2.5 cm distance between electrodes. The following optimum solvent extraction parameters levels were found: Extractant mass of SDDT 100 mg, agitation time 30 min, pH = 8. Under these conditions, the extraction ratio was 97.15%. It was observed that the extraction ratio increases with the increase of SDDT mass. A contacting time of 30 min is considered for ensuring state of equilibrium, and the extraction ratio decreases in a more alkaline medium (pH >8) when the cation of hydrolysis at the aqueous phase was sufficiently disturbed from heating, allowing elements to return to the aqueous phase, thereby decreasing the extraction ratio. After electrowinning is carried out, the results for the experiments were taken to quantitative analysis using the X-ray fluorescence pectrophotometer, scanning electron microscopy, and X-ray diffraction patterns which showed the presence of pure copper at a purity level of 100%.

More than 90% of US Navy Ships are coated with copper ablative paint. These ships may spend long periods of time pier-side, which makes them vulnerable to fouling. Hull grooming has been proposed as a means of maintaining the coatings in an operational condition. This study investigated the effect of grooming on a copper ablative coating exposed statically for six years. Grooming was performed weekly or monthly with controls left ungroomed. The fouling community was visually assessed, dry film thickness measurements were taken to monitor coating loss, and the copper leaching rates were measured. It was found that weekly and monthly groomed surfaces reduced fouling, and the ungroomed surfaces became fully fouled. Coating loss was similar for weekly, monthly and ungroomed surfaces. The results suggest that grooming is a viable method for maintaining copper ablative coatings in a fouling-free condition without adverse increases in the total copper output. [ABSTRACT FROM PUBLISHER]

Hydrometallurgy is the main method to regenerate valuable metals from electroplating sludge and reduce its environmental hazards. As a key step to efficiently recover metals, it is important to choose an environmentally friendly and efficient leaching agent. In this work, four green ionic liquid (ILs) ([BMIm]HSO 4 , [HOOCMIm]HSO 4 , [BSO 3 HMIm]HSO 4 , and [BSO 3 ]Py.HSO 4) were used to leach copper from copper–rich electroplating sludge (C–ES). The tested ILs could effectively leach copper from C–ES, but functionalized ILs have better leaching efficiency, especially sulfonate ILs, which could remove 100% of Cu from C–ES under optimal conditions. Kinetics studies showed that the leaching process of controlled by chemical reaction and material diffusion, and the apparent activation energies were 39.21, 0.98, 14.47, and 41.93 kJ mol−1, respectively. Introducing functional groups (such as carboxyl and sulfonate group) which can complex with metals on cations can enhance the H+ release and complexation ability of ILs, improve the mass transfer efficiency between liquid–solid phase, and thus improve the copper leaching ability by ILs. These findings are of great significance for selecting functional ILs to efficiently regenerate copper and the resource utilization from C–ES. [Display omitted] • An efficient leaching method of copper from electroplating sludge is proposed. • The leaching behavior and the leaching mechanism of copper in ILs was analysed. • Functionalized ILs had better hydrogen release and metal complexation ability. • Sulfonate functionalized ILs is most conducive to copper recovery from C-ES. [ABSTRACT FROM AUTHOR]

The effects of laccase from the white-rot basidiomycete fungus Trametes versicolor on Norway spruce wood (Pices abies) surface were studied. Experiments were performed at room temperature and at pH 4.6, without the addition of mediators. Biological, chemical and physical properties of the treated wood surface were examined by a wood decay test, a scanning electron microscopy (SEEM), a Fourier transform infrared (FTIR) spectroscopy and a copper leaching test. Laccase pre-treatment of Norway spruce wood surface was shown to reduce wood decay by brown-rot fungus, Gloeophyllum trabeum and white-rot fungus, Trametes versicolor. SEM images showed expanded wood cell walls, closed pits and a more even surface after laccase treatment. FTIR analysis indicated that laccase not only catalyse depolymerisation of lignin, but also affect other wood cell wall components, such as hemicellulose and cellulose. We showed that laccase treatment altered wood properties in a way that improved wood resistance to decay and prevented leaching of copper from impregnated wood. [ABSTRACT FROM AUTHOR]

• Electrokinetic leaching of intact rocks using ferric chloride and ferric sulphate. • Distinctly higher recovery (>90%) was achieved with ferric chloride. • Secondary layer formation slowed down leaching rates but did not halt recovery. • Secondary layers found to consist of polysulphides and elemental sulphur. • Preferential formation of soluble polysulphide phases enhances copper recovery. 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. [ABSTRACT FROM AUTHOR]