Copper Recovery Research Articles

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.

Flotation of Copper Sulfide Ore Using Ultra-Low Dosage of Combined Collectors

Copper sulfide ores frequently co-occur with pyrite, presenting a significant challenge for their selective separation during beneficiation processes. Despite advancements in flotation technology, there remains a critical need for efficient methods to enhance copper recovery while suppressing pyrite interference, particularly without compromising the associated precious metals such as gold and silver. Current practices often struggle with achieving high selectivity and recovery while maintaining environmental sustainability. Here, we investigate the efficacy of a ternary collector mixture consisting of ammonium dibutyl dithiophosphate (ADD), butyl xanthate (BX), and ethyl xanthate (EX) for the selective flotation of copper sulfide from a complex ore containing 0.79% Cu and associated precious metals (0.233 g/t Au and 5.83 g/t Ag). A combination of lime and hydrogen peroxide as inhibitors was employed to suppress pyrite effectively under alkaline conditions (pH = 11.33). The results demonstrate that the optimized ternary collector system (ADD:BX:EX at a ratio of 1:0.5:0.5) significantly improves the copper grade and recovery at an ultra-low dosage of 10 g/t. The optimized flotation method using the combined collectors and inhibitors effectively separated chalcopyrite from pyrite, achieving a copper concentrate with 20.08% Cu content and a recovery of 87.73%. Additionally, the process yielded notable recoveries of gold (9.22%) and silver (26.66%). These findings advance the field by providing a viable and environmentally conscious approach to the beneficiation of sulfide ores, potentially serving as a blueprint for processing similar mineral deposits while minimizing reagent usage and costs.

An integrated approach to sustainable mine wastewater treatment: Magnesium recovery with anion exchange membranes

With recent emphasis on sustainable and efficient mineral valorization, novel approaches to treating mineral wastewater in natural settings bring both environmental and economic value. This paper presents the results of an applied research to develop an integrated approach to sustainable wastewater treatment that includes an ion exchange process to recover copper and cobalt from mine wastewater, followed by the membrane recovery of magnesium. The paper investigates magnesium hydroxide crystallization process employing an anion exchange membrane (AEM) cell. This process involves the penetration of OH- ions from the alkaline solution through the AEM to the feed solution in exchange for Cl- ions and precipitation of Mg(OH)2 as solid particles. The wastewater was sampled from different mine waste sources from the copper mine tailings dam in South Australia, all containing significant amounts of critical metals, including magnesium, copper, and cobalt. The results have demonstrated the potential for sustainable magnesium hydroxide recovery methods. The findings suggest that the most influential process parameters for magnesium hydroxide recovery and purity are magnesium concentration in the feed solution and sodium hydroxide to magnesium ratio in the alkaline solution and feed solution, respectively. It was also established that the overall recovery of cobalt, copper and magnesium in a combination of ion exchange and AEM processes was achieved at a level near 100 %. The purity of magnesium hydroxide precipitate was achieved in the range of 90–96.6 % and depends mainly on the presence of impurities in brine.

Recovery of Copper from Secondary Sources Via Regeneration of Synergistic Reactive Extraction of D2EHPA-Cyanex 302 System

Recovery of Copper from Secondary Sources Via Regeneration of Synergistic Reactive Extraction of D2EHPA-Cyanex 302 System

Statistical Evaluation of Flotation Behavior of Chalcopyrite in the Presence of SIPX and Acetoacetic Acid n-Octyl Ester as a Novel Collector Blend: A Sustainable Approach

The chalcopyrite deposit in Malanjkhand, India, is the largest copper ore producer in the country. However, its flotation performance has room for improvement. This study used standard flotation experiments using a mechanical flotation cell using a conventional collecting reagent and a collector blend consisting of xanthate and ester. A three-factor, three-level Box-Behnken design was used to statistically evaluate the experimental design. The obtained data were analyzed using an ANOVA, cubic plots, and response surface methods. The goal was to evaluate the effects and interactions of three key process parameters in chalcopyrite flotation: the dosages of sodium silicate (depressant), sodium isopropyl xanthate (collector), and acetoacetic acid n-Octyl ester (co-collector/modifier). The results implied that introducing acetoacetic acid n-Octyl ester along with minor tweaks in the dosages of sodium isopropyl xanthate helped increase copper grades by at least 15%, with good recovery percentiles. Among the three parameters tested, the copper’s grade and recovery were considerably positively influenced by the AoE dosage in the collector blend. Employing 0.006 kg/t sodium silicate and 0.0065 kg/t sodium isopropyl xanthate with 0.005 kg/t of acetoacetic acid n-Octyl ester, an optimum copper recovery of 88.87% could be achieved. However, with a sodium silicate dosage of 0.0048 kg/t, a SIPX dosage of 0.008 kg/t, and an AoE dosage of 0.005 kg/t, optimized copper grade (1.55%) could be achieved, which is a 78.1% increase from the feed sample grade. To validate the expected results, verification experiments were carried out, and the experimental findings were found to be on at par with the statistical model predictions. Furthermore, the calculated SPI value of 0.0000147cap Kg−1 for a global index per resident lies between 0 and 1.

Mineralogical Characterisation of Copper Slag and Phase Transformation after Carbocatalytic Reduction for Hydrometallurgical Extraction of Copper and Cobalt

Copper smelting slag is a significant potential resource for cobalt and copper. The recovery of copper and cobalt from copper slag could significantly augment the supply of these metals, which are essential to facilitating the transition to green energy while simultaneously addressing environmental concerns regarding slag disposal. However, the complex mineral composition of copper slag poses an enormous challenge. This study investigated the mineralogical and chemical characteristics of copper slag, which are vital for devising the most effective processing techniques. XRD and FESEM-EDS were employed to examine the morphologies of copper slag before and after the reduction process. The effects of borax and charcoal (carbocatalytic) reduction on phase transformation were evaluated. The XRD analysis revealed that the primary phases in the copper slag were Fe2SiO4 and Fe3O4. The FESEM-EDS analysis verified the presence of these phases and yielded supplementary details regarding metal embedment in the Fe2SiO4, Fe3O4, and Cu phases. The carbocatalytic reduction process expedited the transformation of copper slag microstructures from crystalline dendritic to amorphous and metallic phases. Finally, leaching experiments demonstrated the potential benefits of carbocatalytic reduction by yielding high extractions of Cu, Co, and Fe.

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.

Stay with the green: New insights into ancient copper smelting in the Tonglüshan site, China

This paper presents new archaeometallurgical analyses from the Tonglüshan site, a famous ancient mining and smelting site in China. Results show that the primary phases in slag samples from two sites (Sifangtang and Lujia’nao) are all of a vitreous matrix, interspersed with fayalite crystals, wüstite, and hercynite. The trapped metallic particles in the slag are mainly raw copper with few sulfides present, which indicates a direct reduction process of oxidic ore. Iron-rich minerals were likely to be added as flux implied by the few unreacted inclusions in the slag samples. The extremely low copper content in the slag samples demonstrates a high rate of copper recovery, indicating that the copper smelting technology in the region had reached a considerably advanced level. In the meantime, the variations in metal content in slag samples from different periods reveal the diachronic changes in this copper smelting technology. The Tonglüshan site, with its millennia of ancient mining and metallurgical activities, provides an excellent material base for detailed studies on technological evolution.

The Added Value of Copper and Silver Metal from Printed Circuit Boards Waste Using Davis Tube with Variations of Size and Magnetic Intensity

The widespread use of electronic devices has led to a significant increase in electronic waste, including PCB (printed circuit board) waste. PCBs contain valuable metals like copper and silver, which can be reclaimed and reused. Recently, there has been a growing demand for urban mining processes to extract electronic waste PCB Flame Retardant-2 (FR-2) from laptops and computers. During the urban mining process, PCB FR-2 waste undergoes various physical treatments such as dismantling, crushing, and concentration processes. One of the concentration processes involves magnetic separation using a Davis tube. This study aims to investigate the effects of size and magnetic intensity variations on the recovery of copper and silver levels in FR-2 PCB waste. The magnetic concentration process was carried out using different size ranges (-63+100#, -100+150#, -150#) and magnetic intensities (1000 G, 2000 G, 3000 G). The results indicated that the most effective size for separating copper and silver is -63+100# and the optimal magnetic intensity is 1000 G. This resulted in copper and silver content of 45.66% and 0.162%, with recoveries of 80.135% and 62.505% respectively.

Coal to Clean: Comparing Advanced Electrodes for Desulfurization and Copper Recovery

This study explores the electrochemical desulfurization of coal and the recovery of copper (Cu) using dimensionally stable anode (DSA) electrodes. Background: The research addresses the need for effective sulfur removal from coal to reduce emissions. Methods: Electrochemical desulfurization was conducted using DSA and graphite electrodes, evaluating parameters like activation energy, desulfurization rate, and energy consumption. Cyclic voltammetry and linear sweep voltammetry were used to study the electrochemical properties. Results: The DSA electrode demonstrated superior performance with higher desulfurization rates, lower activation energy, and better response to temperature increases compared to the graphite electrode. Optimal desulfurization was achieved at 50 °C with the DSA electrode, balancing efficiency and energy consumption. Copper recovery from the solution post-desulfurization was effective, with an 86.34% recovery rate at −0.15 V vs. (Ag|AgCl). The energy consumption for the Cu recovery was calculated to be 10.56 J, and the total cost for recovering 1 ton of Cu was approximately 781.20 €. Conclusions: The study highlights the advantages of DSA electrodes for efficient sulfur removal and metal recovery, promoting cleaner energy production and environmental sustainability. Future research should focus on optimizing electrochemical conditions and scaling up the process for industrial applications.

Influence of the Use of Ammonium Sulfate and Citric Acid on the Buoyancy of Minerals in Copper-cobalt Plant Process (Case of 635 Deposit Fed at Kambove

The objective pursued in this work is testing the performance of two new reagents namely ammonium sulfate and citric acid, on buoyancy of Kamfundwa ore currently treated at Kambove Concentrator. Optimization tests were conducted in order to determine the optimal doses of reagents commonly used, in this case Sodium hydrosulfide (NaSH), the amylxanthate potassium (KAX), Sodium silicate (Na2SiO3), and the mixture fuel-fatty acid. Metallurgical results obtained with these tests were used as reference for further work. Tests with citric acid alone could not improve the metallurgical results obtained under standard conditions, the same finding was observed in tests with ammonium sulfate alone and that performance seemed to be much closer to those of reference tests. We finally realized flotation tests by combining citric acid and ammonium sulfate in order to streamline the synergy of these two reagents. It appears from these tests that at the dose of 600 g / t of citric acid and 400 g / t of ammonium sulfate, metallurgical performance obtained are better than previously. The following results were achieved during the batch flotation tests: 18.87% as copper content of the head concentrate, with a recovery rate of 55.34%, and 10.81% as copper content of the global concentrate; for a copper recovery corresponding to 80.94%. This mixture of citric acid and ammonium sulfate has allowed good selectivity and a reduction of gangue trained to the concentrate.

Efficient and emission-reduced recovery of high-purity copper from waste enameled copper wires

The escalating demand for refined copper intensifies research into the recycling of copper-based solid waste, exemplified by recovery of copper from waste enameled copper wires (WECWs). Despite its potential, the pyrolysis process for WECWs is hindered by embrittlement, diminishing both recycling yield and quality. Our study pioneers the elucidation of the embrittlement mechanism during WECWs pyrolysis through atom probe tomography and first-principles calculations, revealing that hydrogen, a byproduct of paint film pyrolysis, accumulates at copper grain boundaries, inducing embrittlement by reducing adhesion energy. We introduce two innovative strategies to mitigate hydrogen-induced embrittlement: vacuum pyrolysis and enhanced N2 flow. These approaches significantly reduced hydrogen content from 11.1 % to about 5 % and increased elongation from 2.65 % to 15 %. Moreover, pyrolysis efficiencies of 92.79 % and 91.4 % were achieved, respectively, at temperatures 50 °C lower than conventional methods. Our findings provide crucial theoretical insights into embrittlement and offer effective recovery strategies for copper from solid waste.

Life cycle assessment of decommissioned silicon photovoltaic module recycling using different technological configurations in China

The intricate encapsulation structure and material composition of photovoltaic modules necessitate full materials recycling involving multiple stages and different technological configurations, thereby increasing environmental burden of recycling process. Consequently, environmental impact assessments are imperative. However, previous studies primarily focused on a single technology or compared different technologies within a specific recycling stage, overlooking various technological configurations and thus engendering incomprehensive assessment. Hence, we employ a comparative life-cycle assessment to evaluate the environmental performance of six recycling alternatives with different technological configurations for silicon photovoltaic waste in China, which encompasses five recycling stages and glass/silicon remanufacturing processes. Results shows thermal delamination reduces the normalized environmental impact by 8.73% and 4.62% compared with mechanical and chemical delamination, respectively; electrolysis for metals extraction carries 35.72%–36.35% higher environmental benefits than precipitation. Additionally, introducing silicon/glass remanufacturing provides an additional 6.27%–11.55% environmental benefits. Therefore, integrating disassembly, thermal delamination, leaching & etching, electrolysis, and remanufacturing exhibits the best environmental performance, with −4796 kg CO2-eq/tonne carbon emission and −46400 MJ/tonne energy demand. Environmental hotspots analysis identifies key contributors to environmental impact and benefits. Further sensitivity analysis highlights the importance of enhancing silver and copper recovery efficiency. Finally, targeted strategies are proposed for green recycling routes of photovoltaic waste.

Optimization of Copper Recovery and Fluorine Fixation from Spent Carbon Cathode Reduction Copper Slag by Response Surface Methodology

Optimization of Copper Recovery and Fluorine Fixation from Spent Carbon Cathode Reduction Copper Slag by Response Surface Methodology

Cu(Ⅱ)-EDTA degradation and copper recovery from wastewater in wide pH ranges by an electrooxidation-capacitive deionization system

The treatment and recovery of metal resources from complex industrial wastewater has posed significant challenges due to the presence of multiple heavy metal ions, heavy metal complexes, and acidic conditions. In this study, a novel electrooxidation-capacitive deionization (EO-CDI) system was proposed, which ingeniously harnessed the unheeded Faraday side reaction in capacitive deionization for simultaneous degradation and recovery of copper complexes from wastewater through two electrode integration. Specially, the cathode CuS0.78Se0.22 synthesized through the anionic Se-substitution strategy exhibited a remarkable adsorption capacity up to 672.02 mg/g for Cu ions, outstanding selectivity and stability, particularly in acidic environments. The water oxidation process occurring at the activated carbon anode played a crucial role by generating active species that contribute to the degradation of Cu(Ⅱ)-EDTA, which leaded to the release of copper ions, facilitating their subsequent recovery. Cyclic experiments further confirmed the excellent cyclic stability of the hybrid EO-CDI system, along with its impressive performance in copper extraction when applied to real industrial wastewater. This innovative approach offered promising prospects for addressing the challenges associated with the treatment of complex industrial wastewater and the recovery of valuable metal resources.

Recovery of copper from ammonia–ammonium chloride leach liquor using sterically hindered beta-diketone

In this study, the recovery of copper from ammonia–ammonium chloride (NH3–NH4Cl) leach liquor using sterically hindered beta-diketone (β-diketones), a well-known extractant, was investigated. The experimental approach entails studying how various factors, including extraction time, concentration of the extractant, pH, phase ratio, and temperature, impact the effectiveness of copper extraction. The most favourable conditions for extracting copper from ammoniacal solutions containing 871.27 mg/L Cu2+, 1.75 mol/L NH3, and 0.5 mol/L NH4Cl were determined. Optimal copper extraction was achieved through a one-stage solvent extraction process at a phase ratio of 1 : 1, utilising sulphonated kerosene containing 0.25 mol/L of β-diketones. This extraction process lasted for 10 min and yielded a copper extraction efficiency of 75.10%. Additionally, a stripping ratio of 98.52% was achieved from the loaded organic phase through a one-stage stripping procedure at a phase ratio of 1 : 1, conducted at a temperature of 298 ± 0.5 K.

Selective upcycling of brominated epoxy resin by subcritical water ammonia process with waste copper-based catalyst: Production of high purity methyl pyrimidine/phenols and copper recovery

Tetrabromobisphenol A epoxy resin (TBBPAER) is the main non-metallic component of electronic waste. The scale of electronic waste production and the accompanying TBBPAER waste disposal problems represent a great opportunity for chemical upcycling. But the chemical upcycling of TBBPAER faces great challenges due to its high bromine content and thermally stability. In this study, a subcritical water ammonia (SWA) process combined with waste copper-based catalyst (WCC) selectively converted TBBPAER in high yields (63.46 % at 300°C for 15 min and 73.66 % for 60 min) to low molecular-weight liquid products including high value-added methyl pyrimidine and phenols. The electron transfer among multivalent copper species contained in the WCC promoted the production of free radicals OH, O2−, NH2, and :NH, which resulted in the efficient conversion of TBBPAER and a 99.29 % of debromination ratio. The molecular chain of TBBPAER was snipped by OH and NH2 to produce tetrabromobisphenol A groups (TAG) and ternary carbon groups (TCG). The further degradation of TAG resulted in the producing of phenol chemicals with a purity of 91.8 % (GC peak area%). The further cyclization of TCG induced by :NH produced methyl pyrimidine with a purity of 91.9 % (GC peak area%). The formation of copper ammonia complex led to the leaching/recovery of 86.6 % of copper from the WCC. The SWA-WCC approach demonstrated how TBBPAER waste could be a viable feedstock for the producing of high value-added methyl pyrimidine and phenol chemicals. This study provided a novel sustainable strategy for synchronous treatment/upcycling of the two different wastes of TBBPAER and WCC. The leaching toxicity test of Cu and Zn for the solid residue after the co-treatment showed that their leaching concentrations were much lower than the hazardous waste standard.

A Study on the efficiency of organic activator application to process refractory hard-to-beneficiate raw materials

Polymetallic ores with complex mineralogical compositions pose significant challenges in flotation beneficiation, often resulting in suboptimal separation and recovery of valuable minerals. This study aims to analyse the effectiveness of alkyl benzene sulfonic acid (ABSA) as a frothing activator in improving the flotation performance and mineral recovery of polymetallic ore. It presents the results of flotation beneficiation experiments for polymetallic ore of complex mineralogical composition. Experiments were conducted on polymetallic ore samples using ABSA as the frothing activator in the flotation process. The performance was evaluated based on recovery rates and separation efficiency, comparing the results with standard floating frothing agents. The findings showed the highest efficiency of ABSA application for samples of mixed-type ores in increasing the recovery of gold, copper, zinc and lead in the collective concentrates of flotation beneficiation. ABSA activator promotes additional cleaning of fragments containing valuable metals from oxide films and coatings and the transfer of valuable metals' microparticles due to the organics' adsorption properties and the formation of metal-carbon bonds. Another effect of using this reagent is there was an increase in concentrate mass yield while maintaining the quality parameters. A similar effect was observed for beneficiation of copper ore with complex composition - copper recovery in the main concentrate increased. Selective flotation with the development of gold concentrate from hard-to-beneficiate polymetallic ore also showed a significant increase in gold recovery with ABSA pretreatment.

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.

Life cycle assessment of Al-Cu-Ag-Si recycling process from photovoltaic waste

As raw materials become increasingly scarce, it is important to efficiently recycle PV panels to recover the highest quantity and quality of secondary raw materials. This study evaluates the environmental impact and the related benefits of an innovative process for c-Si PV panels recycling, which permits to recover most of the raw materials contained in them. Life Cycle Assessment analysis was carried out with “grave-to-cradle” perspective. Inventory was supported by data from a pilot plant located in Venice (Italy). ReCiPe 2016 method was used for the impact assessment. The results showed that environmental benefits are due to the recovery of aluminium, copper, silicon, silver and glass. Normalization of impact assessment results demonstrates main relevant impact categories of this process, and gravity analysis underlines what steps in the recycling process mainly contribute to the environmental benefits. Sensitivity analysis showed that quality of recovered materials influences the environmental profile of recycling process.