Copper Leaching Research Articles

Stepwise H*-Mediated and Non-H* Reduction Processes for Highly Selective Transformation of Nitrate to Nitrogen Gas Using a ZVAl-Based Material.

Improving the reduction efficiency and N2 selectivity is important for nitrate decontamination. A novel ternary ball-milled Al-Cu-AC material is reported to achieve a highly selective reduction of nitrate to N2. The reduction process, driven by the continuous dissolution of zero-valent aluminum (ZVAl), demonstrated a stepwise reduction scheme. The interesting shift in the electron-donating pathways was ascribed to the spontaneous change in the microenvironmental pH from neutral to alkaline. The Al-Cu-AC (1:1:5 mass ratio) material completely removed 30 mg/L of NO3--N over a wide pH range (5-9), achieving over 83% TN removal and N2-selectivity, without detectable copper leaching. The atomic hydrogen (H*)-mediated reduction occurring on the Cu component was proven to be crucial for the fast transformation from NO3- to NO2-, while the non-H* reduction process was dominated by the electrochemical reduction of NO2- to N2 on the AC cathode of Al || AC microgalvanic cells formed in the material. The primary reduction route from NO3- to N2 was identified as the *NOH pathway, and the superiority of the Al-Cu-AC material toward nitrate reduction was verified with actual wastewater. This study revealed how microenvironmental pH influenced the electron-donating pathways of ZVAl and provides a new approach to maximize the performance of zero-valent metals.

Statistical Modeling of NaCl and FeSO4 Pretreatment Effect on Refractory Copper Ore Leaching

Black copper oxides, a significant copper resource, present challenges in leaching due to their refractory nature and complex mineralogical composition. This study investigates the sulfation dynamics of the reductive leaching process of black copper ores with the purpose of increasing the copper leaching, focusing on the influences of time and the addition of NaCl and FeSO4 on sulfation behavior. Experiments were designed to replicate industrial conditions using oxidized minerals from the Codelco Salvador hydrometallurgy plant. Multivariate nonlinear regression models and response surface methodology were employed to analyze sulfation behavior. The findings demonstrate that analytical acid consumption (AAC) exerts a consistently positive and statistically significant effect on sulfation across the sampled domain, while NaCl and FeSO₄ also influence the process. However, variations in their levels showed limited impact. Time was significant only within the 24–48 h range. The optimized model predicted maximum sulfation at 60 h with 60% AAC, 90 g NaCl, and 42 g FeSO₄, with strong alignment between the observed and predicted values. These insights emphasize the importance of pretreatment methods, including sulfuric acid curing and NaCl addition, in improving leaching efficiency.

Dielectric Permittivity in Copper Leaching: A Review

The leaching process for copper extraction has garnered significant attention due to its critical role in meeting the rising demand for copper, driven by global trends towards decarbonization and electrification. The accurate measurement of variables is essential for process control, prompting the development of advanced sensor technologies. This paper reviews the applications of dielectric permittivity measurements in the mining industry, focusing on their potential to enhance the monitoring and optimization of copper leaching processes. It evaluates the suitability of permittivity-based sensors, analyzing their advantages and limitations, and discusses the implications for process control and economic optimization. The study highlights the integration of permittivity measurements into existing monitoring systems, aiming to improve efficiency, reduce environmental impact, and increase ore recovery rates. This comprehensive review provides insights into the current state of permittivity measurement technologies and their future prospects in the context of copper leaching.

Water quality performance of vegetated compost blankets for highway stormwater management: Particulate matter and trace metals.

Urban stormwater pollution poses serious risks to human and environmental health, including trace metals toxicity. To improve the performance of existing highway Vegetated Filter Strips (VFS), which have limited performance for volume reduction and pollutant removal, amendment with a Vegetated Compost Blanket (VCB), a layer of seeded compost, has been proposed. A novel VCB/VFS system was assessed as a Stormwater Control Measure (SCM) via particulate matter and trace metals removal performance. Field and greenhouse studies of the VCB/VFS system were conducted and concentrations of total suspended solids (TSS), filtered and total copper, and total zinc were analyzed. Thirty-three representative field storm events were sampled over a period of 2.25years. Significant TSS removal was observed in both the field and greenhouse studies, with effluent particles likely flushing from the media itself and the majority of effluent concentrations below the water quality target of 25mg/L. Particulate copper, and likely particulate zinc, were also largely concurrently removed. Dissolved trace metals performance was mixed, and differences in initial compost copper content was likely influential in observations of dissolved copper leaching in the field which was not observed in the greenhouse. Despite positive performance for particulate matter and associated trace metals removal from stormwater, potential detriment to downstream water bodies due to dissolved copper leaching is a concern. Before widespread implementation, compost composition and potential for dissolved trace metals release should be thoroughly considered, as well as the age and ability of the VFS to immobilize dissolved metals.

Study on the Chlorination Leaching of Gold and Copper from High Gold-Containing Material Based on Variable Stirring Speed

Study on the Chlorination Leaching of Gold and Copper from High Gold-Containing Material Based on Variable Stirring Speed

Tin, silver, and copper sulfate compound extraction from lead-free solder dross by reduction with petroleum coke, electrorefining, cementation, and crystallization process

Solder dross, a waste by-product from the electronic component dipping bath, contains significant quantities of valuable metals. This study presents a four-step process for recovering tin, silver, and copper from lead-free Sn-Ag-Cu solder dross. The process involves the initial reduction of the dross using petroleum coke to produce an anode plate, followed by electrorefining to extract tin from the anode plate. Selective leaching of silver and copper from the residual anode slime and cementation techniques are employed to recover silver powder. The rest of the copper solution was used to synthesize copper sulfate crystals. Experimental results demonstrate optimal conditions for the reduction process, resulting in a high tin recovery rate of 92.88%. The electrorefining step yields tin with a purity of 99.94%. Silver and copper are successfully recovered from the anode slime, achieving purities of 99.60% for recovered silver powder and 99.90% for crystallized copper sulfate compounds. This comprehensive study offers insight into the efficient extraction and recovery of tin and other valuable metals from lead-free solder dross.

Oxidative Dissolution Behavior of Synthetic Chalcopyrite with Non-Stoichiometric Compositions

Chalcopyrite (CuFeS2) is the most important Cu mineral, accounting for 70% of copper reserves in the world. Cu metal is primarily produced from chalcopyrite-containing ores by an extraction process involving flotation, pyrometallurgy, and electrorefining. Owing to the ongoing depletion of high-grade ores, hydrometallurgical processes involving copper leaching from chalcopyrite-containing ores using acidic ferric sulfate solutions have been intensively studied. However, efficient copper leaching remains a challenge, and the details of the dissolution mechanism of chalcopyrite in natural resources remain unclear.Investigation using synthetic minerals with controlled compositions and morphologies is an effective approach for understanding the dissolution mechanism. In this study, we prepared dense pellets of synthetic chalcopyrite with stoichiometric and non-stoichiometric compositions and compared their oxidative dissolution behaviors in an acidic ferric sulfate solution.The nominal compositions of the prepared samples are Cu0.250Fe0.250S0.500 (stoichiometric composition), Cu0.240Fe0.260S0.500, Cu0.245Fe0.260S0.495, and Cu0.265Fe0.245S0.490. The powder samples were synthesized via a high-temperature reaction using Cu wire, Fe wire, and S powder as raw materials. The dense pellets (diameter 10 mm and thickness of approximately 3 mm) were obtained by pulse current pressure sintering and subsequent annealing at 500 ℃. Density measurements and scanning electron microscopy observations revealed that the morphologies such as grain size and density of the obtained pellets were almost constant, regardless of the nominal composition. In X-ray diffraction analyses, the diffraction peaks of the obtained pellets were consistent with the chalcopyrite phase (CuFeS2, PDF #00-037-0471). The scanning electron microscopy with energy dispersive spectrometry analysis confirmed that no other phase was detected in the Cu0.250Fe0.250S0.500, Cu0.240Fe0.260S0.500, and Cu0.265Fe0.245S0.490 pellets.To enable electrochemical measurements, dense pellets were cut and embedded in resin after connecting the copper leads. Obtained electrode samples were immersed in 0.1 M Fe(SO4)1.5 – 10−4 M FeSO4 – 0.18 M H2SO4 at 70 ℃ for 24 h. The concentration of Cu ions in the solution was determined by inductivity coupled plasma atomic emission spectrometry and the dissolution rates of the samples were evaluated. The corrosion potentials of the synthesized chalcopyrite samples were also measured. shows the measured dissolution rates and corrosion potentials. The Cu dissolution rates for the chalcopyrite samples with non-stoichiometric compositions (Cu0.240Fe0.260S0.500, Cu0.245Fe0.260S0.495, and Cu0.265Fe0.245S0.490) were over one order of magnitude than those for the samples with stoichiometric composition (Cu0.250Fe0.250S0.500). This result demonstrates that a small difference in composition significantly affects the dissolution rate in the ferric sulfate solution. The corrosion potentials of the electrodes with non-stoichiometric compositions were less noble than those of the stoichiometric composition sample. At the corrosion potential, the rate of anodic dissolution of the chalcopyrite phase was equal to that of the cathodic reaction of the oxidant in the solution (mainly the reduction rate of the Fe(III) species). Considering the shift in the corrosion potential, increasing the dissolution rate is attributed to the enhancement of the anodic dissolution reaction of the chalcopyrite phase by the change in its composition from stoichiometry. Figure 1

Selective catalytic reduction (SCR) of NOx with NH3 over the SSZ-13/ZSM-5 intergrowth zeolite

An intergrowth zeolite combining the SSZ-13 and ZSM-5 structure was synthesized using a dual-template method for application in selective catalytic reduction (SCR) of NOx with NH3. The intergrown structure was confirmed through detailed characterization. Compared to pure-phase zeolites, the intergrowth exhibited up to a 14 % enhancement in NO conversion at temperatures above 220 °C after hydrothermal aging (at 750 °C with 10 % H2O for 16 h). Comprehensive characterization revealed that intergrowth zeolite promoted the transformation of hydrothermally less stable Cu species (ZCuOH, located at 8 MR) to hydrothermally more stable Cu species (Z2Cu, located at 6 MR) during hydrothermal ageing. Additionally, copper leaching is hindered due to the well-preserved structural integrity of the intergrowth zeolite, with only a slight decrease in crystallinity (∼1.6 %). These findings suggest that intergrowth zeolites are promising candidates for mitigating NOx emissions in stationary sources under harsh hydrothermal conditions, such as that found in thermal power generation and steel manufacturing.

Copper-saturated chitosan beads (CuSCBs) for Enhanced phosphate removal

This study investigates the sequential use of non-cross-linked chitosan beads (CBs) for copper and phosphate adsorption, emphasizing copper site saturation and selective phosphate binding. Initially, CBs were loaded with copper until saturation was achieved, where all available sites were occupied by copper at an initial concentration of 100 mg/L. These copper-saturated chitosan beads (CuSCBs) were subsequently applied for phosphate adsorption, achieving a maximum adsorption capacity of 85.89 mg/g at pH 5. X-ray Photoelectron Spectroscopy (XPS) analysis revealed a shift in the Cu2O binding energy to lower values upon phosphate adsorption, indicating that phosphate ions interact primarily with the copper ions intercalated on the CBs rather than the chitosan matrix. Additionally, the nitrogen spectra showed no shift, confirming that the amine groups of chitosan do not participate in phosphate binding. The findings suggest a 1:1 interaction ratio between copper and phosphate ions, with each phosphate ion binding to one copper ion, creating a stable and selective adsorption site. The adsorption data fit the Langmuir isotherm and pseudo-second-order kinetic models, suggesting a homogeneous monolayer adsorption mechanism driven by chemisorption, where each copper site on the chitosan surface selectively binds one phosphate ion. Furthermore, the CuSCBs demonstrated minimal copper leaching and retained 90 % of their phosphate adsorption capacity over multiple adsorption–desorption cycles, highlighting their potential as effective and reusable adsorbents for water treatment applications targeting copper and phosphate removal.

Safety Assessment on the Proposed Inclusion of Up to 75% Inert Copper in a PARNUT Bolus (RP2059)

An application was submitted to the Food Standards Agency in May 2023 to extend the scope of the conditions of use associated with an existing feedstuff for particular nutritional purposes (PARNUT). Intraruminal boluses can be used to provide a long-term supply of trace elements and vitamins to grazing animals, specifically ruminants with functional rumen. Under this use, they are classified as a PARNUT. Up to 20% inert, non-bioavailable iron can be added to the bolus as a means to increase density and ensure that the bolus is retained in the reticulum of the animal. The applicant proposed the inclusion of up to 75% inert, non-bioavailable copper in a bolus as an alternative to iron. To support the Food Standards Agency (FSA) and Food Standards Scotland (FSS) in evaluating the dossier, the Advisory Committee on Animal Feedingstuffs (ACAF) were asked to review the dossier and the supplementary information from the applicant. The FSA/FSS concluded, based on the ACAF’s advice, that copper in a bolus ballast is inert and that leaching of copper into the rumen is highly unlikely. The copper in a bolus ballast is not bioavailable to the animal, therefore the risk of toxicity to target animals and consumers is low. The use of up to 75% inert copper as an alternative to up to 20% inert iron in a PARNUT bolus poses no additional risk to the target animals, consumers, users or the environment. The views of the ACAF have been taken into account in the safety assessment which represents the opinion of the FSA and FSS.

Cu (ii) Immobilized on Mesoporous Poly (Guanidine–Triazine–Sulfonamide) (PGTSA/Cu): A New Catalyst for the Synthesis of Tetrazolo[1,5‐a]pyrimidines

ABSTRACTThe study focuses on the synthesis and characterization of a new mesoporous polysulfonamide stabilizer using condensation polymerization and the nanocasting technique. The resulting material, PGTSA, was modified with copper ions and used as a nanocatalyst in the reaction of benzaldehydes, 1H‐tetrazole‐5‐amine, and malononitrile. The performance of the mesoporous PGTSA/Cu (II) was compared with non‐porous PGTSA/Cu (II), highlighting the significance of support porosity in catalytic activity and loading of copper species. Based on the analysis of the ICP and catalytic performance, it was observed that mesoporous PGTSA/Cu (II) exhibited a higher level of catalytic activity compared to PGTSA/Fe3O4/Cu (II) and non‐porous PGTSA/Cu (II). Also, the catalytic activity of the aryl aldehyde was significantly influenced by its electrical characteristics. The recovery and reusability of the PGTSA/Cu (II) catalyst are noteworthy aspects, highlighting the practicality and sustainability of the catalytic system. The amount of copper in fresh catalyst and the recycled catalyst after six times recycling is 1.57% and 1.52%, respectively. Therefore, ICP‐OEIS analysis indicated that copper leaching of this catalyst is very low. The procedure offered high product yields, easy recovery of the nanocatalyst, remarkable reusability, short reaction times, and compatibility with various substrates.

A potential strategy for eco-friendly and efficient copper recovery: Ferricyanide-enhanced glycine leaching of copper

E-waste contains significant amounts of metal elements, particularly copper. Efficient and eco-friendly recovery of copper is essential for both the resourceful utilization of e-waste and the mitigation of environmental pollution. Glycine leaching is a green method for copper recovery, but the use of conventional oxidants suffers from slow reaction kinetics and low leaching yields. Herein, by introducing ferricyanide ([Fe(CN)6]3−) as an oxidant in the glycine leaching of copper, the efficient dissolution of copper was realized. Electrochemical measurements and various physical characterizations demonstrate that the [Fe(CN)6]3− oxidant effectively increases the initial potential of the solution by forming a [Fe(CN)6]3−/[Fe(CN)6]4− redox couple. This promotes the rapid oxidation of Cu to Cu2+, facilitates the formation of soluble copper complexes with gly−, and prevents the development of an oxidized passivation layer on the copper surface, resulting in efficient copper dissolution. Compared to 0.15 M H2O2, the addition of 0.01 M [Fe(CN)6]3− increased the initial potential of the solution from 192.33 mV to 489.30 mV and raised the dissolved copper concentration from 225.60 ppm to 330.40 ppm after 24 h. The “potential enhancement” effect of ferricyanide in this work provides an effective strategy for efficient copper recovery.

Hydroxy-Carboxylic Acids as Green and Abundant Ligands for Sustainable Recovery of Copper from a Multimetallic Powder: A Proof of Concept.

The recovery of copper and other valuable metals had become increasingly strategic for the future of the global economy, particularly in regions lacking abundant mineral resources, such as most European countries. In this study, we investigated the viability of utilizing environmentally friendly, cost-effective, abundant and bio-based ligands, specifically carboxylic acids and their derivatives, for copper leaching in a low-temperature hydrometallurgical process. Our investigation focused on elucidating the impact of substituents in the α position of hydroxy-carboxylic acids on copper solubilization efficacy. Notably, hydroxy-carboxylic acids, like malic acid and lactic acid, were evidenced as particularly promising ligands for leaching copper from a custom-made multimetallic powder. By thoroughly characterizing the obtained complexes (Raman, UV-Vis) and by supporting the experimental efforts by a Design of Experiment (DoE) approach, we optimized the leaching process. The influence of experimental parameters such as pH, temperature, leaching time, and Cu/ligand molar ratio on process yield (determined through Inductively Coupled Plasma - Optical Emission Spectroscopy, ICP-OES, analysis) was thoroughly investigated. Additionally, we developed a subsequent copper recovery step by precipitating copper (II) hydroxide in an alkaline environment, guided by speciation diagrams tailored for each copper-ligand system.

The synergistic actions of copper/l-glutamine co-grafting in improving anti-biofouling and desalination performances of reverse osmosis thin film composite membrane

There have been ongoing efforts to improve membrane surfaces by adding specific functional groups through physical or chemical approaches to minimize fouling propensity. This study introduces a facile grafting and deposition approach to enhance the performance of thin film composite polyamide reverse osmosis (TFC PA RO) membrane. The synergistic effects of l-glutamine and Cu nanoparticles in altering the physico-chemical properties and improving desalination performances were investigated. The l-glutamine improved the hydrophilicity of membrane, while Cu NPs offered significant antibacterial characteristics to improve the functionality of membrane. The findings revealed that TFC-l-glutamine/Cu3 showed optimum performance with water flux of 16.5 L.m−2 h−1 and salt rejection of 96.8 % at an operating pressure of 1.5 MPa. The TFC-l-glutamine/Cu3 membrane exhibited an absence of dense colonies against both S. aureus and E. coli, on account of the antibacterial effectiveness of Cu NPs. The S. aureus- and E. coli-fouled TFC-l-glutamine/Cu3 membrane showed the lowest flux decline of 20 % and 25 % for, respectively. The TFC-l-glutamine/Cu3 membrane exhibited promising antifouling performance, with a flux recovery ratio (FRR) of 95.2 % for bovine serum albumin (BSA) foulants. The TFC-l-glutamine/Cu3 membrane exhibited a low copper leaching of ≤3 %, suggesting its high stability. The modification strategy demonstrated in this study provides a feasible solution to simultaneously address multiple issues of TFC RO membranes, which potentially leading to more efficient desalination.

Enhanced geopolymerization of MSWI fly ash through combined activator pretreatment: A sustainable approach to heavy metal encapsulation and resource recovery

With the rapid pace of socioeconomic progress, there has been a continuous rise in the generation of municipal solid waste incineration (MSWI) fly ash. Enhancing the efficiency of MSWI fly ash utilization, minimizing expenses, and developing more cost-effective and environmentally sustainable cementitious materials represent critical scientific challenges that warrant immediate attention. The research commenced with the preliminary treatment of MSWI fly ash using a blend of chemical activators and a water rinsing method. Following this, quicklime and coal fly ash were incorporated to formulate a geopolymer derived from MSWI, aimed at stabilizing the MSWI fly ash. Throughout this investigation, a selection of five chemical activators—calcium hydroxide, sodium hydroxide, sodium silicate, dilute sulfuric acid, and citric acid—was employed in conjunction with a water-washing procedure to condition the MSWI fly ash. Three single factor experiments denoted A, B, and C, were designed, and the corresponding geopolymer samples were prepared. In this research, the analysis focused on the solidified MSWI fly ash-based geopolymer samples, examining their physical and chemical characteristics, compressive strength, levels of heavy metal release, and the structure at a microscopic level. The findings revealed that the B3 series exhibited the most substantial 28-day compressive strength, reaching 1.692 MPa. Concurrently, the concentrations of leached heavy metals, including zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), cadmium (Cd), and nickel (Ni), were all beneath the regulatory thresholds stipulated by the GB16889 and GB18598 criteria, signifying a notably effective solidification outcome. During the geopolymerization process, gel phases such as calcium aluminosilicate hydrate (C-A-S-H) and calcium silicate hydrate (C-S-H) are formed within the geopolymer matrix. This leads to the formation of a compact and cohesive cementitious material, which showcases superior mechanical strength and a robust capacity for heavy metal sequestration. This research contributes to the safe management of MSWI fly ash by not only facilitating its non-hazardous disposal but also enabling the efficient containment and elimination of heavy metals, chloride ions, and elemental aluminum.

The combined leaching of copper, gold and uranium in chloride solutions. II. Concentrate leach tests

This study of the simultaneous leaching of copper, gold and uranium from a flotation concentrate is aimed at establishing the conditions that could be applied in a possible heap leach process that would recover all three metals (plus silver, if present) in a single step. The results obtained in this study confirm the results obtained in Part I (Nicol et al., 2024) that enhanced rates for leaching of chalcopyrite from flotation concentrates from two different sources can be obtained in acidic chloride solutions in the presence of chlorate ions. The measurements of the solution potentials during leaching with chlorate are similar to those obtained previously and confirm that chlorine generated by the chlorate-chloride reaction is the active oxidant.Uranium is dissolved even in the absence of chlorate by iron(III) as the oxidant. The latter is re-generated by reaction of iron(II) with chlorate. The dissolution of gold requires higher potentials, and it is only leached when the potential approaches 1.0 V in concentrated chloride solutions. At low chloride concentrations (1 M), gold is not dissolved because of apparent passivation.An electrochemical study of the behaviour of gold in chloride solutions in the presence of sulfide ions has shown that the passivation is probably the result of the formation of a layer of Au2S on the gold surface at low potentials before the addition of chlorate to the leach solutions i.e., before the generation of sufficient chlorine concentrations. At potentials above about 0.95 V Au2S is unstable being oxidised to AuCl2− and elemental sulfur thereby eliminating passivation.

The combined leaching of copper, gold and uranium in chloride solutions. I. Chalcopyrite

In a study (Part II) aimed at the simultaneous heap leaching of copper (predominantly chalcopyrite), gold and uranium from an ore, it was found that this could be achieved using chlorate as the oxidant in chloride solutions. As a result, a more detailed study has been made using electrochemical and batch leach tests on pure chalcopyrite electrodes under typical heap leach conditions.The use of chlorate at moderately low concentrations has shown that enhanced rates of dissolution of chalcopyrite can be maintained over periods up to 4 days at ambient temperatures in acidic chloride solutions. The rate of dissolution is enhanced at higher acid concentrations. The rate in the presence of chlorate does not appear to depend on the iron(III) (and presumably the copper(II)) concentration.The observed rates are significantly greater than those predicted for oxidative dissolution from the electrochemistry and the mixed potential model. An alternative non-oxidative mechanism has been revisited to account for this difference.A preliminary measurement has been made of the kinetics of the oxidation of hydrogen sufide and iron(III) by low concentrations of chlorine produced by reaction of chlorate with chloride ions. These reactions are rapid, and theory shows that they would support the proposed non-oxidative mechanism.

Fungal Leaching of Iron (Fe), Zinc (Zn), and Copper (Cu) in Copper Ore Waste from Ikalamavony, Madagascar, by Aspergillus sp.

The recovery of waste has become a global concern due to the economy's shift towards a circular economy, which includes the recycling of mining waste. This study aims to highlight the ability of the fungus Aspergillus to dissolve metals as iron, zinc, and copper from Ikalamavony ore waste through the bioleaching process for their recovery. The waste was subjected to granulometric analysis to classify the grains by weight and size, and the metal content was analyzed using Flame Atomic Absorption Spectrophotometry (FAAS). Bioleaching was conducted in two stages: first, the fungi were cultured on Sabouraud agar or broth medium at 28°C for 7 days, then the produced organic acids were recovered and the waste was placed in these acids. The optimization of certain parameters as particle size, sucrose content, medium volume, strain incubation time and bioleaching time was considered. The FAAS analysis results indicated that the waste contained an average of 5.35% Fe, 0.05% Zn, and 18.14% Cu. The optimum parameters obtained for each metal were as follows: for particle size, Fe and Zn: 125 µm; Cu: 200 µm; for sucrose content, Fe: 7.5 g and Zn, Cu: 12.5 g; for the volume of culture medium, Fe, Zn, Cu: 150 ml. The incubation time for the strains was 7 days. With these optimizations, the extracted metals were 73.89% Cu, 56.77% Zn, and 7.89% Fe for a leaching time of 15 days. These results confirm that bioleaching using Aspergillus sp. is an effective technique for the extraction and recovery of copper and zinc from ore waste.

Leaching Thermodynamics of Low-Grade Copper Oxide Ore from [(NH4)2SO4]-NH3-H2O Solution.

This paper describes a highly alkaline low-grade copper oxide ore. Copper can be selectively leached out while other metals are retained. A thermodynamic model of the CuO-(NH4)2SO4-NH3-H2O system was established for the leaching of tenorite (CuO) under conditions of mass and charge conservation. MATLAB's fitting functions, along with the diff and solve functions, were used to calculate the optimal ammonia concentration and total copper ion concentration of tenorite under different ammonium sulfate concentrations. The effects of various ammonia-ammonium salt solutions (ammonium sulfate, ammonium carbonate, ammonium chloride) on the copper leaching rate were investigated. Results show that under the conditions of an ammonia concentration of 1.2 mol/L, an ammonia-ammonium ratio of 2:1, a liquid-solid ratio of 3:1, a temperature of 25 °C, and a leaching time of 4 h, the copper leaching rate from the ammonium sulfate and ammonium chloride solutions reaches 70%, which is slightly higher than that of ammonium carbonate. Therefore, an ammonia-ammonium sulfate system is selected for leaching low-grade copper oxide due to its lower corrosion to equipment compared to the chlorination system. The impact of this study on industrial applications includes the potential to find more sustainable and cost-effective methods for resource recovery. The industry can reduce its dependence on resources and mitigate its environmental impact. Readers engaged in low-grade oxidized copper research will benefit from this study.

A low-temperature co-treatment of diethylhexyl phthalate-rich polyvinyl chloride and waste copper catalyst by subcritical water (hydrothermal treatment): Dechlorination, recovery of diethylhexyl phthalate and copper

As one of the most widespread plastics in the world, the recycling of diethylhexyl phthalate-rich polyvinyl chloride (DEHP-rich PVC) faces great challenges because of the high levels of Cl and plasticizers. On the other hand, waste copper catalyst (WCC) discharged from various industrial processes is not effectively recycled. In this study, a significant synergistic effect between the DEHP-rich PVC and WCC was found in a subcritical water (SubCW) medium, and a co-treatment of the DEHP-rich PVC and WCC was developed by the SubCW process. The introduction of WCC significantly improved the dechlorination efficiency of the DEHP-rich PVC to 96.03 % at a low temperature of 250 °C. Under the optimal conditions, the leaching of copper from WCC reached a maximum of 81.08 %. Oil products included DEHP (55.7 %, GC peak area%), 3-methyl-3-heptene (37.3 %, GC peak area%), and 2-ethyl-1-hexanol (7.0 %, GC peak area%). The dechlorination pathways of the DEHP-rich PVC included hydroxyl substitution and direct dechlorination. HCl released from the DEHP-rich PVC led to a decrease in the pH of the system and significant copper leaching from the WCC. DEHP was decomposed by hydrolysis, dehydration, and rearrangement reaction by the SubCW co-treatment process. The enhancement mechanism of the WCC for the dechlorination of the DEHP-rich PVC was based on that the conversion of copper species in the SubCW promoted the formation of hydroxyl radicals and the hydroxyl substitution for chlorine in PVC molecular chain. The proposed SubCW low-temperature co-treatment could be a prospective strategy for the low-energy and synchronous recovery of the two different wastes of the DEHP-rich PVC and WCC.