Copper Recovery Rate Research Articles

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.

High-value terminal treatment: Utilizing copper slag heat in the manufacture of copper-containing weathering steel

Copper slag, a bulk non-ferrous solid waste, is critical in establishing a closed-loop cycle in the copper metallurgy industry. Currently, the processing techniques for copper slag are characterized by prolonged procedures, secondary waste discharge, limited value utilization, and high energy consumption. A novel approach was proposed to harness the thermal energy inherent in molten copper slag for producing copper-bearing weathering steel and cement while simultaneously synergistically recovering lead and zinc. The results indicate that under the conditions of smelting temperature of 1500 °C, alkalinity of 1.06, smelting time of 60 min, and mechanical stirring, the recovery rates of copper, iron, lead, and zinc in copper slag reached 98.83%, 99.59%, 97.45%, and 98.51%, respectively. Furthermore, the feasibility of this approach was validated by laboratory-scale preparation of Q355GNH-grade copper-bearing weathering steel and S95-grade cement clinker. Computational analysis for the direct carbothermal reduction of molten copper slag in its thermal state reveals that, compared to the traditional flotation process, this approach saved 1177 MJ of thermal energy per metric ton of copper slag, equivalent to a reduction of 147 kg of carbon dioxide emissions. This study facilitates the zero-waste, high-value, and sustainable development of the copper smelting industry.

Interphase migration and enrichment of lead and zinc during copper slag depletion

An interphase migration and enrichment model of lead and zinc during molten copper slag depletion was established. The occurrence of various components in copper slag was predicted using sulfur−oxygen potential calculations and confirmed through high-temperature experiments. The recovery rate of copper can reach 90.13% under the optimal conditions of 1200 °C, an iron to silicon mass ratio of 1.0, 3 wt.% ferrous sulfide, and a duration of 45 min. Lead (54.07 wt.%) and zinc (17.42 wt.%) are found in the flue dust as lead sulfate, lead sulfide, and zinc oxide, while copper matte contains lead (14.44 wt.%) and zinc sulfide (1.29 wt.%). The remaining lead and zinc are encapsulated as oxides within the fayalite phase.

Flotation-assisted electrodeposition process to recover copper from waste printed circuit boards

Electrodeposition is an attractive method to recover copper from waste printed circuit boards (WPCBs), which preferably requires metal-rich concentrate as raw material. In this study, a metal-rich route for WPCBs was established to assist copper electrodeposition by using flotation method. Different from aqueous disperse medium in conventional flotation, we proposed ethanol as a disperse medium to improve dispersivity and sustainability. An H-type electrolytic cell with a cation exchange membrane was used to electrolyze copper in metal-rich concentrate at the anode and recover pure copper on the cathode. The experiments were conducted to investigate the effect of grade on the proportion of metal-rich concentrate after flotation and the electrodeposition rate of copper, and the key factors (solid-to-liquid ratio and applied voltage) affecting copper electrodeposition were evaluated. The results show that the flotation with ethanol can greatly enrich copper, and the copper content in metal-rich concentrate can be increased by 182.3 %, with a copper recovery rate of 85.1 %. Increasing the solid-to-liquid ratio and applied voltage can increase the deposition rate of copper, but affects the stability of electrodeposition. The optimized electrodeposition parameters are: electrolyte temperature of 50℃, solid-to-liquid ratio of 25 g/L, and applied voltage of 10 V. The purity of copper in electrodeposits can reach over 99 %.

A cost-effective and short process for copper recovery from WPCBs of mobile phones by slurry electrolysis: Semi-scale certification

Waste printed circuit boards (WPCBs) are considered as the most complex and valuable part of the discarded mobile phone. Alkaline slurry electrolysis is certified as an effective method to recover copper from WPCBs of mobile phones (WPCB-MPs). To promote its industrial application, 5000 mL scale trials were conducted and the results show that: Electrolysis at 30 g/L WPCB-MPs, 25 g/L Cu2+(CuSO4·5H2O), 4 mol/L NH3·H2O, 0.5 mol/L NaCl, 0.5 mol/L NH4Cl, 20 mA/cm2 and 298 K for 8 h, the current efficiency is 90.47 %, the copper recovery is 92.04 %, and the purity of cathode copper is 99.79 %. Electrolyte circulation hardly affected current efficiency, copper recovery rate and copper purity, which were higher than 90 %, 90 %, and 99 %, respectively. The semi-scaled experiment demonstrates its feasibility in industrial application. Primarily cost analysis shows that producing a ton of cathode copper has a profit of about $5,144.5. Therefore, alkaline slurry electrolysis has a broad industrial prospect in WPCBs recycling.

Energy and copper recovery from acid mine drainage by microbial fuel cells. Effect of the hydrochar doping on carbon felt anodes

This work investigates the performance of a Microbial Fuel Cell (MFC) for Acid Mine Drainage (AMD) treatment using bare and hydrochar-doped carbon felt (CF) anodes. Hydrochar was synthesized through hydrothermal carbonization of Spergularia rubra, followed by activation at 500 °C, resulting in improved O/C and H/C ratios of 0.26 and 0.78, respectively. The study reveals that doping CF anodes with non-activated and activated hydrochar significantly enhances copper recovery and electricity generation. The highest copper recovery rate of 16.0 mg/L h−1 was achieved with activated hydrochar-doped CF (CFaH) anodes, followed by 10.6 mg/L h−1 with non-activated hydrochar-doped CF (CFnaH) anodes, and 7.1 mg/L h−1 with bare CF anodes. Hydrochar doping also improved the maximum current density to 0.21 mA cm−2 compared to 0.16 mA cm−2 with bare CF anodes. These results demonstrate the potential of hydrochar-doped CF anodes for efficient metal and energy recovery from AMD, offering a sustainable and energy-efficient alternative to conventional methods.

Adsorption of Heavy Metal from Wastewater by Bioabsorbent Modified Azolla microphylla and Lemna minor

Environmental toxicity from rapid industrialization raises concerns about water pollution caused by industrial waste and urban sewage. Aquatic macrophytes, such as the Azolla species, have shown promise in absorbing heavy metals and nutrients from water. This study introduces a novel approach by evaluating Azolla Microphylla and lemna minor as an economical adsorbent for copper removal from rivers. Moreover, this study stands out by conducting thorough characterization analyses. The adsorbent material underwent XRD, SEM, BET, and FTIR analyses after being crushed and sieved to 1-2 mm. Copper was extracted from river water using UV-Vis detection at 285 nm. Optimal conditions for adsorption were determined at pH 4, 30 minutes of contact time, and 0.4 g of adsorbent. Copper concentrations in the Sungai Petani, Sungai Selangor, and Sungai Langat ranged from 2 mgL-1 to 5 mgL-1. Azolla proves effective as a copper adsorbent due to its simplicity in sample preparation, time-saving benefits, cost-effectiveness compared to conventional systems, and high copper recovery rate. By successfully removing copper, a prevalent heavy metal contaminant in industrial waste and urban sewage, this research contributes to achieving Sustainable Development Goal 6 for clean and safe water supplies.

Iron Oxide-Copper Mineral Associations in Supergene Zones: Insights into Flotation Challenges and Optimization Using Response Surface Methodology.

In this study, batch flotation tests were conducted to investigate the flotation of oxidized copper ore from the supergene zone of the Bounhas deposit. Utilizing the Response Surface Methodology (RSM) anchored on the Box-Behnken Design (BBD), the effects of parameters such as collector dosage, sulfidizing agent, copper oxide and iron oxide grades, and particle size on copper recovery were explored. ANOVA and response surface plots elucidated the complex behavior of copper flotation. Mineralogical analyses of the initial feed and postflotation tails were performed on an industrial scale using advanced Zeiss microscopy. The quadratic model with an R 2 of 94.49% accurately captured the impact of the process parameters on copper recovery. Among the key findings, the sulfidizing agent exhibited the most substantial quadratic effect, while the copper oxide grade had the most substantial linear impact on recovery. A pivotal observation was the link between copper losses in tailings and specific iron oxide-copper associations. Optimization identified conditions leading to a maximum copper recovery rate of 71.49%. When validated industrially, the model demonstrated robust applicability for analogous mineral processing contexts. The study's mineralogical insights enhance our understanding of the supergene zone mineralization and offer a solid foundation for subsequent in-depth mineral processing studies.

Numerical Simulation of Stacked Step Flowincentrifugal Force Field for Copper Ore Separation

In this study, the flow field of a stacked step flow device was simulated using Fluent 19.2 software. The simulation results show that: the combination of rotational motion and reverse fluidization of the fluid in the cone of the equipment makes the slurry dispersed and separated in the radial direction, and the upward motion of the fluid can promote the solid phase, especially the smaller particle size and lower density of the silica phase, to realize the separation of the copper phase and the silica phase in the axial direction; the vortex generated by the sudden change of tangential flow velocity at the step can significantly improve the settling efficiency of the copper phase in the upward process. Fluent simulation results show that: when the rotational speed is 50r/min, the feed speed is 0.5m/s, and the reverse fluidization speed is 0.018m/s, the copper recovery rate is 87.70%, and the enrichment ratio is 13.45.

Slag chemistry, element distribution behaviors, and metallurgical balance of e-waste smelting process

The co-smelting of electronic waste (e-waste) in copper/lead pyrometallurgical processes is widely recognized as the preferred solution for sustainable development. However, aluminum and halogen elements in e-waste causes new challenges. To address this, the slag chemistry of high Al2O3-containing slag was studied, and the distribution behaviors of Au, Ag, Sn, and other elements in the copper alloy/slag/gas system were investigated in the presence of halogen elements (F/Cl/Br) using the equilibration method. The industrial practice of electronic waste smelting was modeled using METSIM, and the material and energy balances of one industrial process were obtained. Under the conditions of electronic waste smelting, the solubility of Al2O3 in the FexO–SiO2–Al2O3–CaO slag system decreased with increasing CaO content. When the CaO content was 20 wt%, and the Fe/SiO2 mass ratio was 0.62–0.95, the solubility of Al2O3 in the slag reached 20 wt%. When 1%–10% CaF2 was added, 93% of Au entered the metal phase. When the same amount of CaCl2 or CaBr2 was added, up to 32% Au entered the gas phase. When CaF2 was added to the system, 22%–49% of Ag entered the gas phase. However, when CaCl2 or CaBr2 was added, 3%–34% of Ag entered the gas phase. The proportion of tin in the gas and slag phases increased with increasing temperature or the addition of halides. The METSIM simulation results showed that under optimized conditions, the crude copper contained more than 90 wt% copper, the discharged slag contained approximately 0.5 wt% copper, and the recovery rates of copper, gold, and silver were ≥98%. The heat generated from raw materials and fuel accounted for the largest part of the heat income, representing 65.32% of the total.

Copper recovery from waste printed circuit boards by NH3−(NH4)2S2O8–CuSO4 slurry electrolysis

The recovery of waste printed circuit boards (WPCBs) is always at the center of the issue of e-waste, and even “urban mining”. Slurry electrolysis has been certified as a new and efficient approach for directly recovering copper from WPCBs, although its current efficiency is not high. Therefore, an alkaline slurry electrolysis system with NH3−(NH4)2S2O8–CuSO4 was examined to improve the current efficiency because (NH4)2S2O8 produces SO4-· or ·OH in an alkaline environment. Factors such as the current density, concentration of NH3·H2O, (NH4)2S2O8, NaCl, and Cu2+, solid/liquid (S/L) ratio, and electrolysis time are discussed. The results showed that the NH3−(NH4)2S2O8–CuSO4 electrolyte could significantly impact the current efficiency and copper recovery rate. Under optimum conditions (4 mol/L ammonium hydroxide, 1 mol/L ammonium persulfate, 20 g/L copper ion(Ⅱ), 0.5 mol/L sodium chloride, S/L ratio of 30 g/L, 20 mA/cm2, and 3 h), the copper recovery rate was 90.10%, and the copper current density was significantly improved to 83.03%, which was considerably higher than that of the acidic slurry electrolysis system (approximately 70%). Because copper in the WPCBs and Cu2+ can form [Cu(NH3)2]+ with ammonia and ammonia persulfate, it is substantially easier to electrodeposit than [Cu(NH3)4]2+. Meanwhile, the purity of the obtained copper foil was > 99.986%, meeting the standard for commercial cathodic copper, and markedly higher than that of the acidic slurry electrolysis system. Thus, alkaline slurry electrolysis shows great potential for applications in the e-waste industry.

Study of Factors Affecting the Copper Ore Leaching Process

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%.

Comprehensive Recovery of a High-sulfur Copper-gold Ore in Shandong

The raw gold grade of a mine in Shandong is 1.42 g/t, and it is accompanied by copper and sulfur minerals, and the embedding is closely related, so it is difficult to obtain the ideal index using the original flotation process. In order to realize the effective recovery of gold, copper, and sulfur, the test study of mixing-separation flotation and priority flotation is carried out. The results show that the mineral is more suitable for the beneficiation process of mixing-separation flotation. The recovery rate of gold, copper, and sulfur is 70.42%, 93.58%, and 68.85%, and the recovery rate is 22.89% higher than the priority flotation. The produced copper and gold mixed concentrate and sulfur concentrate can be directly sold to realize the effective recovery of gold, copper, and sulfur.

Electrolyte circulation: Metal recovery from waste printed circuit boards of mobile phones by alkaline slurry electrolysis

Alkaline slurry electrolysis has been verified as an effective method for metal recovery from waste printed circuit boards (WPCBs). However, the electrolyte that remains after slurry electrolysis contains high concentrations of metal, which can cause pollution without suitable treatment. Most importantly, the metals in the electrolyte are not completely recovered, resulting in wasted resources and increased costs. Here, the feasibility of circulating this electrolyte and its effect on copper recovery, current efficiency, and purity, is discussed. We also describe in detail the migration and transformation of copper and other metals, such as nickel, zinc, and lead, during the preparation of high-purity cathode copper from mobile phone WPCBs (WPCB-MPs) using an ammonia-ammonium chloride slurry electrolysis system. Experimental results from 19 cycles of electrolyte reuse show that copper is mainly distributed in the cathode products, whereas other metals are mainly distributed in the electrolyte and anode residues. With an increase in the number of cycles, the concentration of other metals in the electrolyte gradually increased, showing metal enrichment. The current efficiency fluctuates but is usually >90%. In addition, the copper recovery rate and purity were essentially unaffected, being >99% and >99.9% for all 20 runs, respectively, and all the cathode copper foils were easily peeled off. This study demonstrated that electrolytes can be reused for metal recycling from WPCB-MPs by alkaline slurry electrolysis without decreasing Cu purity, Cu recovery rate, and current efficiency. Thus, this study provides a green and cost-effective process for recycling resources from e-waste.

Multi-Objective Optimization of Copper Bioleaching: Comparative Study of Pure and Co-Cultured Cultivation.

Bioleaching is a practical method to recover metals from low-grade mineral sulfides. The most frequent bacteria involved in the bioleaching of metals from ores are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Experimental design is a method through which the optimum activity condition will be obtained, avoiding numerous trials and errors. This study aimed to optimize the bioleaching condition of two indigenous iron- and sulfur-oxidizing bacteria from the Meydouk mine, Iran, and evaluate their function in a semi-pilot operation in pure and mixed cultures. After treatment with sulfuric acid, the bacterial DNA was extracted, and further 16S rRNA was sequenced to characterize the bacterial species. The cultivation condition of these bacteria was optimized using Design-expert (6.1.1 version) software. The copper recovery rate and the differentiation in the ORP rate in the percolation columns were also investigated. These strains were isolated from the Meydouk mine for the first time. 16S rRNA analysis revealed that both bacteria belong to the Acidithiobacillus genus. The factors with the most significant impact on Acidithiobacillus ferrooxidans with their optimum level were temperature=35 °C, pH=2.5, and initial FeSO4 concentration=25 g.L-1. Also, initial sulfur concentration had the most significant impact on Acidithiobacillus thiooxidans with the optimum level of 35 g.L-1. Moreover, the mixed culture determined higher bioleaching efficiency compared with the case of employing the pure cultures. Utilizing a mixture of both bacteria, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans elevated the Cu recovery rate due to the synergetic function of the strains. Also, introducing an initial dosage of sulfur and pre-acidification could elevate metal recovery efficiency.

NOx removal and copper recovery from the leaching process for waste printed circuit boards: performance evaluation and potential environmental impact assessment.

Resource recovery is crucial for small- and medium-sized enterprises to attain a circular economy. The economic benefits of recovering precious metals from electronic waste, such as waste printed circuit boards (WPCBs), are hindered by secondary pollutant emissions from pretreatment processes. This study aims to recover copper from the WPCB acid leaching process and reduce NOx emissions through the use of a high gravity rotating packed bed (RPB). The results indicate that the copper recovery ratio increases to 99.75% through the displacement reaction between iron powder and copper nitrate. The kinetic analysis of copper dissolution was employed to simulate the NOx emissions during acid leaching, with an R-squared value of 0.872. Three oxidants, including H2O2(aq), ClO2(aq), and O3(g), with pH adjusted to different NaOH concentrations, were used to remove NOx. The greatest NOx removal rate was achieved using a 0.06M NaOH solution, with a removal rate of 91.2% for ozone oxidation at a 152-fold gravity level and a gas-to-liquid (G/L) ratio of 0.83. The gas-side mass transfer coefficients (KGa) for NOx range from 0.003 to 0.012 1/s and are comparable to previous studies. The results of a life cycle analysis indicate that the NOx removal rate, nitric acid recycling rate, and copper recovery rate are 85%, 80%, and 100%, respectively, reducing the environmental impact on the ecosystem, human health, and resource depletion by 10% compared to a scenario with no NOx removal.

Development of one-step process method to separate tin from tin-refining sulfur slag via vacuum sulfuration and volatilization

Sulfur slag is a dangerous solid waste generated during tin refining. To ensure environmental safety, sulfur slag must be treated. As a result, a novel one-step process method was proposed and developed for clean and efficient recovery of tin and copper from sulfur slag. The method was based on the thermal stability of pyrite to simultaneously sulfurize and volatilize tin, which greatly improved the reaction efficiency. The feasibility of the one-step separation of tin and copper was confirmed by theoretical calculations such as Gibbs free energy and saturated vapor pressure. The effects of temperature, pyrite dosage, system pressure, and holding time were experimentally studied. Finally, the volatile was stannous sulfide, and the residue was cuprous and ferrous sulfides. The optimal experimental conditions were as follows: the reaction temperature was 1273 K, the pyrite addition ratio was 40%, the system pressure was 10 Pa, and the holding time was 3 h. The direct recovery rates of tin, copper, and iron were 99.95, 99.77, and 99.57%, respectively. The removal rates of tin, copper, and iron were all above 99.8%. The vacuum sulfuration and volatilization method provides a novel process for the clean and effective cyclic treatment of tin-refining sulfur slag.

Investigation of the process of leaching copper from copper-containing dumps using bio-oxidants

The paper presents the results of experiments on bulk copper leaching with preliminary bacterial oxidation of initial ore. As a culture of bio-oxidant, we used A.ferrooxidans. Studies on the adaptation and cultivation of a technologically efficient strain of A.ferrooxidans have been carried out. As an alternative chemical oxidizer, the use of trichloroisocyanuric acid (THCC) was considered. Standard sulfuric acid leaching served as a control option. As a result of the application of the chemical oxidation method using THCC, an increase in the extraction of copper into solution compared to other options was observed only during the first 10 days. As a result, over 30 days of leaching, the copper recovery rate was 52,83%. During the same period, 62,17% of copper was extracted by standard sulfuric acid leaching. The greatest efficiency was observed in the variant of preliminary bacterial oxidation. During 30 days of leaching, 76,08% of copper was extracted into the productive solution. At the electrolysis stage, 30,8 g of copper was deposited on the cathode from the accumulated electrolyte solutions, which gives a current recovery equal to 94,6%.

Dynamic global feature extraction and importance‐correlation selection for the prediction of concentrate copper grade and recovery rate

AbstractLarge‐scale industrial data have brought great challenges to data calculation and analysis. Feature extraction and selection have become one of the research emphases in data mining. To mine the dynamic characteristics of large‐scale industrial data, a dynamic global feature extraction (DGFE) method integrating principal component analysis (PCA) and kernel principal component analysis (KPCA) is proposed such that the achieved feature set is not only dynamic but also contains linear and non‐linear features. To ensure that the obtained feature set is optimal with the minimum redundancy, a new importance‐correlation‐based feature selection (ICFS) method is proposed. To verify the validity and feasibility of the proposed methods, the partial least square (PLS) and least square support vector machine (LSSVM) prediction models for the concentrate copper grade and the recovery rate are established. The effectiveness of the proposed methods is verified through data experiments on a copper flotation industrial process.

Separation and recovery of tin and copper from tin refining sulfur slag using a new process of airtight sulfuration – Vacuum distillation

Sulfur slag is a high-value hazardous waste produced during the refining process of crude tin. To reduce the emission of wastewater, harmful gas, and hazardous residue, a theoretical and experimental investigation was carried out to develop a new process for converting metal to metal sulfide that utilizes physical differences (saturated vapor pressure) for separation. Here, a sulfur slag processing approach based on airtight sulfuration-vacuum distillation is proposed. In this paper, the Gibbs free energies of the sulfuration reaction of tin and cuprous sulfide and the decomposition reaction of copper sulfide are calculated, the saturated vapor pressure of each substance is analyzed, and the composition of the products is predicted. By adding sulfur to sulfur slag, the composition of the substances in the slag was regulated, and efficient separation of tin and copper was achieved based on the difference in volatility of the compounds. The optimum sulfur addition amount, sulfuration temperature and time, and volatilization temperature and time were investigated using airtight sulfuration and vacuum distillation experiments. The results show that tin and cuprous sulfide were thoroughly sulfurated when 20 g sulfur was added, the airtight sulfuration temperature was 573 K, and the holding time was 4 h. Stannous sulfide volatilizes violently above 941 K and volatilizes completely at 1273 K. The purities of stannous sulfide and cuprous sulfide obtained by the airtight sulfuration-vacuum distillation experiment were 99.02% and 99.30%, respectively. The direct recovery rates of tin and copper were 99.93% and 99.91%, respectively. The removal rate of copper in the volatiles was 99.84%, and the removal rate of tin in the residue was 99.96%. The method thoroughly separated tin and copper from sulfur slag, significantly reducing the environmental and economic costs compared to those of the traditional process.