Secondary Copper Production Research Articles

Econometric modeling for the influence of economic variables on secondary copper production in India

The stocks and flows of primary metal resources, and the estimates of so generated secondary scrap metal flows are tracked and analysed utilizing the traditional analytical method of ‘material flow analysis’. However, the scrap availability and hence the secondary metal production is also influenced by fluctuating economic conditions. Here we utilize the autoregressive distributed lag approach to model the influence of selected economic variables on secondary metal production and hence the scrap availability in the country. We find electricity index, mining index, and electric power generation and distribution correlate with secondary copper production in long-run; and electricity index correlate with secondary copper production in short-run. A 1% increase in electricity index initially leads to 1.76% drop in secondary copper production in short-run, and 3.69% increase in secondary copper production in long-run. A 1% increase in both mining index, and electric power generation and distribution leads to 4.57% and 5.18% decrease in secondary copper production in long-run respectively. The CUSUM and CUSUMSQ charts show the developed ARDL model to be stable over time. Based on the model dependence, we suggest that the policy makers shall devise policies towards reducing copper mining activities thereby encouraging stakeholders to focus on effective collection and efficient recycling of copper towards conservation of natural metal resources.

Analysis of China's non-ferrous metals industry's path to peak carbon: A whole life cycle industry chain based on copper

Copper is an essential nonferrous metal, and the adjustment of its whole industry chain structure is conducive to realizing a carbon peak in the nonferrous metal industry. We have performed a life cycle assessment to calculate the carbon emissions of the copper industry. Based on the carbon emissions scenarios of shared socioeconomic pathways (SSPs), we have utilized material flow analysis and system dynamics to analyze the structural changes in the copper industry chain from 2022 to 2060 in China. The results show that (1) the flows and in-use stocks of all types of copper resources will increase significantly. The overall copper supply may meet demand around 2040–2045 due to secondary copper production potentially replacing primary copper production to a large extent, and trade supply is the primary pathway for meeting copper demand. (2) The total carbon emissions from the regeneration system are the smallest (4 %), followed by the production and trade subsystems, accounting for 48 %. The embodied carbon emissions from copper product trade in China have expanded annually. (3) Under the SSP scenario, the copper chain carbon emission peak will be achieved by approximately 2040. Based on a balanced copper supply and demand scenario, the recycled copper recovery efficiency must reach 84.6 %, and the energy structure (the proportion of non-fossil energy in electricity) must reach 63.8 % by 2030 to achieve the carbon peak target for the copper industry chain in China. The above conclusions indicate that actively promoting adjustments in the energy structure and resource recovery processes may help encourage the carbon peak of nonferrous metals in China by realizing the carbon peak of the copper industry.

The Impact of Inelastic Collisions with Hydrogen on NLTE Copper Abundances in Metal-poor Stars

We investigate the non-local thermodynamic equilibrium (non-LTE, hereafter NLTE) analysis for Cu i lines with the updated model atom that includes quantum-mechanical rate coefficients of Cu + H and Cu+ + H− inelastic collisions from the recent study of Belyaev et al. The influence of these data on NLTE abundance determinations has been performed for six metal-poor stars in a metallicity range of −2.59 dex ≤ [Fe/H] ≤ −0.95 dex. For Cu i lines, the application of accurate atomic data leads to a decrease in the departure from LTE and lower copper abundances compared to that obtained with Drawin’s theoretical approximation. To verify our adopted copper atomic model, we also derived the LTE copper abundances of Cu ii lines for the sample stars. A consistent copper abundance from the Cu i (NLTE) and Cu ii (LTE) lines has been obtained, which indicates the reliability of our copper atomic model. It is noted that the [Cu/Fe] ratios increase with increasing metallicity when ∼−2.0 dex < [Fe/H] < ∼−1.0 dex, favoring a secondary (metallicity-dependent) copper production.

Measuring environmental impacts from primary and secondary copper production under the upgraded technologies in key Chinese enterprises

Copper is a strategic resource to support China's low carbon transition and economic development. China must meet its high copper demand with its limited copper reserve, indicating that it is essential to promote sustainable copper resource management by encouraging secondary copper supply. However, both primary and secondary copper production result in significant environmental impacts. Thus, it is urgent to evaluate such impacts so that appropriate mitigation pathways can be identified. This study conducts life cycle assessment (LCA) at the corporate level to measure the environmental impacts of both primary and secondary copper production. Results show that the total environmental impact from secondary copper production accounted for 7.7%–14.3% of that from primary copper production. Human carcinogenic toxicity is the most significant environmental impact for both primary and secondary copper production. Electricity is the dominant contributor to such environmental impacts. Factors that lead to such environmental impacts are also identified, suggesting that it is critical to increase secondary copper production. Finally, several policy recommendations are proposed to facilitate sustainable copper resource management in China.

Hydrometallurgical Recycling of Copper Anode Furnace Dust for a Complete Recovery of Metal Values

Copper anode furnace dust is waste by-product of secondary copper production containing zinc, lead, copper, tin, iron and many other elements. Hydrometallurgical Copper Anode Furnace dust recycling method was studied theoretically by thermodynamic calculations and the proposed method was verified experimentally on a laboratory scale. The optimum condition for leaching of zinc from dust was identified to be an ambient leaching temperature, a liquid/solid ratio of 10 and H2SO4 concentration of 1 mol/L. A maximum of 98.85% of zinc was leached under the optimum experimental conditions. In the leaching step, 99.7% of lead in the form of insoluble PbSO4 was separated from the other leached metals. Solution refining was done by combination of pH adjustment and zinc powder cementation. Tin was precipitated from solution by pH adjustment to 3. Iron was precipitated out of solution after pH adjustment to 4 with efficiency 98.54%. Copper was selectively cemented out of solution (99.96%) by zinc powder. Zinc was precipitated out of solution by addition of Na2CO3 with efficiency of 97.31%. ZnO as final product was obtained by calcination of zinc carbonates.

Hydrometallurgical Treatment of Converter Dust from Secondary Copper Production: A Study of the Lead Cementation from Acetate Solution

The subject of interest in this study was lead cementation with zinc from solution after conventional agitate acidic leaching of converter dust from secondary copper production. The kinetics of lead cementation from an acid solution of lead acetate using zinc powder was studied. The optimal cementation conditions for removing lead from the solution were determined to have a stirring intensity of 300 rpm, a zinc particle size distribution &lt;0.125–0.4&gt; mm and an ambient temperature. Under these conditions, an almost 90% efficiency in removing lead from solution was achieved. The cementation precipitate contains Pb, and a certain amount of Cu. Lead is present in the cementation precipitate in the PbO, Pb5O8 and Pb(Cu2O2) phases. The solution after cementation was also refined from copper. The solution can be used for further processing in order to obtain a marketable Zn-based product. The resulting cementation precipitate can be further processed and modified to obtain a lead-based product. A kinetic study of the process of lead cementation from solution was also carried out. Based on experimental measurements, the value of apparent activation energy (Ea) which was found to be ~18.66 kJ·mol−1, indicates that this process is diffusion controlled in the temperature range 293–333 K.

Evaluation of econometric models of secondary refined copper supply

Copper is essential in attaining a sustainable development path due to its prominent role in the electromobility and renewable energy industries. In 2019 refined copper usage was 23.5 million tons, of which primary copper supplied 86.3%, and the remaining 13.7% was provided by secondary metal. In the future, copper recycling would increase significantly concerning primary copper supply to meet the goal of decreasing greenhouse gases emissions. Secondary copper production reduces energy consumption by 85% and greenhouse gas emissions by 65% compared to average primary sources.This study analyzes seven econometric models described in the literature that tried to explain the supply of secondary refined copper worldwide (SRC). Furthermore, this study assesses the forecasting capacity of these models in the short and long-term. Although the explanatory variables selected by previous researchers are theoretically supported, they failed to fully explain SRC. An empirical analysis for the period 1960–2017 confirmed that only two of the eight studied explanatory variables shown to be causal of SRC in the short-term. The re-estimation of the coefficients shows high instability when the number of variables or observations changed, making it difficult to analyze the future market and to assess public policies. Although the explanatory variables share the same long-term trend (cointegrated series), they do not properly forecast the future when evaluated using the Backcasting methodology.Based on these results, it is possible to improve the explanatory and predictive power of the analyzed models and reduce their average error.

Removal of Copper, Nickel, and Iron from Lead–Tin Composite by Segregation of Intermetallic Silicon Phases

In the reduction stage of the secondary copper production process, copper, nickel, lead, and tin are collected in a “black copper”, while zinc is volatilized and precipitated as ZnO in the flue dust. The slag coming from this reduction stage is low in valuable metals and is disposed. In the conversion stage, lead and tin are oxidized and incorporated in the slag phase; in accordance with the oxygen potential, this “converter slag” also contains higher contents of copper and nickel. This slag is then reduced in two stages. From the first stage, a copper–nickel metal is returned to the converter stage, and in the second stage, a crude PbSn composite with copper contents of around 10% and nickel contents of around 2.5%, as well as a further usable slag, is obtained from the “secondary” slag. Iron is used as a reducing agent, so that the metal obtained can contain iron of up to over 10%, depending on the reduction duration. The motivation of this investigation is to provide a method for the subsequent refining of the raw PbSn composite, with the aim of obtain a saleable PbSn composite as well as returning the copper and nickel contents quantitatively to the main copper route or to sell them as an alloy. Therefore, the present work aims to investigate the refining of the raw PbSn composite by the separation of the copper, nickel, and iron via the segregation of intermetallic phases. For that, a series of experiments were performed on the formation and subsequent segregation of intermetallic phases, by introduction of an additional element to the system. The results indicated sharper separation of PbSn composite and copper, nickel, and iron due to the higher thermodynamic stability of these phases (selectivity).

Analyzing the environmental impact of copper-based mixed waste recycling-a LCA case study in China

Copper-based mixed wastes include copper-containing wastes from the chemical, metallurgy, copper processing, printing, electronic component manufacturing, and other industries. Copper-based mixed wastes have high humidity and a significantly lower copper content than general waste copper, pose serious environmental hazards, and are very difficult to recover. The recycling of copper-based mixed wastes has important economic and environmental significance. Chinese companies have started extracting copper and other metals from copper-based waste mixtures and have achieved a high economic efficiency. This paper assesses the environmental impacts of copper-based mixed waste recycling and suggests possible optimization measures for the production process with respect to environmental impacts. The life cycle assessment (LCA) method is adopted to evaluate the effects of different production processes and to compare the environmental impacts of copper recovery from copper-based mixed waste recycling to the environmental impacts of primary and secondary copper production. Sensitivity analysis is conducted to estimate and evaluate the effects of possible production process optimization measures on environmental impacts. The results show the following: 1) The environmental impact of the copper-based mixed waste recovery process is generally superior to that of primary copper production in China on average, while it is inferior to that of secondary copper production. For example, the fossil energy consumption in primary copper production accounts for 74.9% of the impact of this process. 2) Smelting is the production process with the greatest environmental impact throughout the life cycle of copper-based mixed waste, accounting for 64.5% of the normalized index of the total environmental impact; and electrolysis and zinc recovery reach 19.8% and 12.1% of the total normalized index, respectively. 3) The raw materials and emission components with the largest environmental impacts are the carbon emissions from coal use and carbon dioxide emissions during smelting, the use of electricity during electrolysis, and the use of heavy oil and lime as raw materials during refining; these five items account for 69.7% of the total environmental impact. Thus, efforts at process improvement should focus on the full life cycle of energy utilization in the smelting process and on energy and material depletion in the refining and electrolysis processes. Specific process improvements and simulation analyses are important directions for further research.

PCDD/Fs emissions from secondary copper production synergistically controlled by fabric filters and desulfurization.

The effects of fabric filters and desulfurization systems during secondary copper smelting on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) concentrations, emission coefficients, and profiles were studied in an oxygen-rich smelting furnace and an anode furnace. In the anode furnace, the toxic equivalent (TEQ) concentration ranges were 0.106-1.04ng World Health Organization (WHO)-TEQ/m3 at the fabric filters inlet and 0.027-0.17ng WHO-TEQ/m3 at the outlet. For the oxygen-rich smelting furnace, the TEQ concentration ranges were 1.21-1.93 and 0.010-0.019ng WHO-TEQ/m3 at the desulfurization system inlet and outlet, respectively. The TEQs in the outlet stack gases of the desulfurization system from the anode furnace were 0.0041-0.016ng WHO-TEQ/m3. It is likely that PCDD/Fs that were taken away from the stack gases were adsorbed by the fly ash and gypsum. Solid residues were the dominant release routes for PCDD/Fs. PCDD/Fs congener and homologue profiles of stack gases from different smelting stages were similar. The contributions of more chlorinated homologues from the anode furnace decreased observably after the stack gases passed through the fabric filters. However, the desulfurization process did not greatly change the PCDD/Fs homologue profiles. Overall, both the fabric filters and desulfurization systems showed excellent removal efficiencies for PCDD/Fs in the stack gases, which reduced the TEQ emissions to well below the 0.5ng WHO-TEQ/m3 to achieve standard discharge.

NLTE analysis of high-resolution H-band spectra IV: neutral copper

To obtain reliable Cu abundances with the APOGEE H-band spectra, it is important to investigate the non-local thermodynamic equilibrium (NLTE) effects on the formation of the H-band Cu I lines. In addition, the Cu atomic model needs to be tested. Based on both the high-resolution and high signal-to-noise ratio H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and optical data, we derived the LTE and NLTE copper abundances of 13 FGK sample stars with the spectral synthesis method. We find that the NLTE effects are negligible for the Cu I 16005.7Å line in the IR H-band. Consistent copper abundances within the uncertainties from these two sets of lines have been obtained, which indicates the reliability of our NLTE copper atomic model. We note that the [Cu/Fe] ratios increase with increasing metallicity when ∼ – 1.4 dex < [Fe/H] < ∼ – 0.5 dex, favoring a secondary (metallicity-dependent) copper production.

Assessing the future environmental impacts of copper production in China: Implications of the energy transition

Copper demand in China is expected to grow considerably over the coming decades, driving energy use and environmental impacts related to copper production. To explore the environmental impacts of copper production in China, we used a variant of Life Cycle Sustainability Analysis that combined the Life Cycle Assessment methodology with the Chinese copper demand projections from 2010 to 2050. The results indicate that the environmental impacts of pyrometallurgical copper production are expected to increase more than twofold during this period and remain the largest contributor to the environmental footprint. Secondary copper production emits the least pollutions. Increasing the share of secondary copper production is the most environmental friendly option for copper production. To this end, China may focus on improving the classification of waste copper products and recycling infrastructure for end-of-life management. Hard coal use and production are crucial contributors to climate change in the context of copper production. Cleaning up copper production processes and improving energy efficiency would also help reduce environmental impacts. Energy transition can significantly reduce the environmental impacts of copper production, but it also can increase copper requirement.It does not visibly contribute to reduce human toxicity as well.

Laser-induced breakdown spectroscopy analysis of the free surface of liquid secondary copper slag

The present study focuses on the in-situ analysis of slags from secondary copper production by means of laser-induced breakdown spectroscopy (LIBS) in order to improve the process efficiency and the end product quality. Synthetic slag samples, simulating secondary copper production slags, were melted in a laboratory induction furnace and were analyzed using LIBS. SiO2 and FeO were the major components and Al2O3, ZnO and CuO were introduced in the synthetic slag as minor components with concentrations below 10 wt%. The solidified samples were analyzed by means of X-ray wavelength dispersive spectroscopy in an electron probe micro analyzer (WDS-EPMA) and the obtained elemental composition was used as reference for the construction of calibration curves for the elements of interest, i.e. Si, Fe, Al, Zn and Cu. The quality of these calibration models was evaluated by the coefficient of correlation (R2). The accuracy was estimated by means of the prediction error percentage obtained from cross-validation of the calibration curves as well as by external validation using samples originating from industry. The last samples were melted under the same conditions as those of the laboratory prepared samples, and LIBS spectra were collected from the free surface of their melts. Furthermore, the solidified industrial samples were analyzed by WDS-EPMA and the determined concentrations were compared with the ones obtained using LIBS. Results were obtained for SiO2, FeO, ZnO and CuO with the accuracies better than 13.5%, which are considered as satisfactory. The quantification of Al2O3 was significantly influenced by self-absorption. The limits of detection (LOD) of the elements with respect to their oxides, i.e. SiO2, FeO, Al2O3, ZnO and CuO, were estimated as 1.5 wt%, 1.0 wt%, 0.097 wt%, 0.15 wt% and 0.012 wt%, respectively, which are appropriate for the targeted application.

Variations of PCDD/Fs emissions from secondary nonferrous smelting plants and towards to their source emission reduction

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are cancerogenic organic pollutants that priority controlled by Stockholm Convention with globally 183 signatories now. Secondary nonferrous smelting plants are confirmed to be important sources in China due to its large industrial activities and high emissions of PCDD/Fs. It is important to prioritize source to achieve source emission reduction by conducting field monitoring on typical case plants. Here, the emission profiles and levels of PCDD/Fs were investigated in 25 stack gas samples collected from three secondary copper production (SeCu), two secondary zinc production (SeZn) and two secondary lead production (SePb). Both average mass concentration and toxic equivalency quantity (TEQ) concentrations of PCDD/Fs all generally decreased in the order: SeCu > SeZn > SePb. It is noteworthy that the mean TEQ concentration in stack gas from SeCu with oxygen-enrich melting furnace technology, at 2.7 ng I-TEQ/Nm3, was much higher than the concentrations of other smelting processes. The average emission factors and annual release amounts of PCDD/Fs from SeCu, SePb and SeZn investigated were 28.4, 1.5, 10.4 μg I-TEQ/t and 1.03, 0.023, 0.17 g I-TEQ/year, respectively. The ratios of 2,3,7,8-TCDF to 1,2,3,7,8-PeCDF and OCDD to 1,2,3,7,8,9-HxCDD varied to large extent for three metal smelting, which could be used as diagnostic ratios of tracing specific PCDD/Fs sources. Addition of copper-containing sludge into the raw materials might lead to higher PCDD/Fs emissions. It is important to emphasize and reduce the PCDD/Fs emissions from oxygen-enrich melting furnace from secondary copper productions.

Characterization of dusts from secondary copper production

Various types of waste, including dusts, are produced in the pyrometallurgical production of copper from secondary raw materials. According to the European Waste Catalogue and Hazardous Waste List, dusts from secondary copper production are classified as hazardous waste. In secondary copper production 3.87 million tons of copper were produced worldwide in 2017. The dusts are produced in the following thermal operations: reduction of the melt in the shaft furnace (shaft furnace dust), converting (converter dust), and pyrometallurgical refining (refining dust). These dusts contain significant amounts of heavy metals (Zn, Pb, and Sn) in oxidic forms. The dusts are regarded as secondary raw materials, and it is necessary to look for ways of extracting these heavy metals. The aim of this work was to characterize the individual types of dust and determine their quantitative and qualitative composition. The content of heavy metals in copper shaft furnace dust is (52.16% Zn, 19.33% Pb), in copper converter dust (32.40% Zn, 14.46% Pb), and in refining dust (32.99% Zn).

State of art control of dioxins/unintentional POPs in the secondary copper industry: A review to assist policy making with the implementation of the Stockholm Convention

Article 5 of the Stockholm Convention requires that each Party shall take measures to reduce the releases from anthropogenic sources of unintentional persistent organic pollutants (UPOPs), with the goal of their continuing minimization and, where feasible, their ultimate elimination. A major source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and other unintentional POPs releases, both in China and worldwide, is the metal industry in particular secondary metal industries such as copper smelting. More than 50% of the global secondary copper production is now in China and high levels of PCDD/Fs are released from these operations with the national inventory of China reporting a total of 1133.8 g toxic equivalents (TEQ) yr−1. Consequently the Global Environment Facility (GEF) is supporting the project ‘UPOPs Reduction through best available techniques and best environmental practices (BAT/BEP) in the secondary copper production sector’ in China compromising >50% of the global secondary copper production. As part of this project, information on relevant UPOPs from the metal industry have been reviewed and is presented here. This information should also be useful for other (developing) countries for controlling UPOPs releases from metal industries. This review and the information it contains provides a robust resource for policy makers, the industry and researchers to improve secondary copper production to BAT/BEP standards in relation to the reduction of PCDD/Fs and other UPOPs release. The contents include the details required to assist the understanding of the formation of chlorinated UPOPs along with their brominated and brominated-chlorinated analogues. It reviews the international sources of information on BAT/BEP, including the integrated approach considered in the European BAT Reference document, and shows how this can be used to achieve an overall reduction of pollutant releases from the industry. The current national standards of PCDD/F limits to air, water and solid residues have been compiled and are also included. Challenges which need to be addressed, such as the current international lack to consider brominated and mixed bromo-chloro PXDD/Fs which might be more environmentally significant than PCDD/Fs in some facilities – are also discussed.The study includes a brief description of the steps China has taken to change the national regulatory framework and to improve the sustainability of its secondary metal industry. The Stockholm Convention BAT/BEP guidelines recommend consideration of integrated pollution prevention and control and sustainable production as general principles which parties may incorporate when applying the BAT/BEP guidelines and guidance. This holistic approach is considered in the current project and in the improvement of the pilot facilities and will also be considered in the replication of experiences in other facilities. Using this approach ensures the implementation of the Stockholm Convention can contribute to integrated pollution prevention and control, the development of a circular economy and consequently to genuinely sustainable development thus contributing to different sustainable development goals (SDGs). It is hoped this approach will be adopted in other developing and transition economies and thus help to achieve improvements of the secondary metal industry globally.

Polychlorinated naphthalene (PCN) emissions and characteristics during different secondary copper smelting stages

The amounts and characteristics of polychlorinated naphthalenes (PCNs) emitted by a secondary copper smelter were investigated. Differences in the amounts and characteristics of PCNs emitted during different smelting stages were investigated, and the main stage during which PCNs were emitted was identified. PCN concentrations in stack gases emitted during secondary copper smelting were 477.0–762.5 ng/m3 (4.4–8.3 pg toxic equivalents/m3). The contributions of the different stages to total PCN emissions decreased in the order feeding–fusion stage (65% of total PCN emissions) > oxidation stage (27%) > deoxidation stage (8%). The main contributor to PCN emissions during secondary copper smelting was the feeding–fusion stage. PCN concentrations and profiles in stack gas, fly ash, and deposit ash collected during different smelting stages were determined. PCNs in stack gases were mainly less-chlorinated homologs, and fly ash and deposit ash were dominated by highly-chlorinated homologs. These results will help improve strategies for decreasing and eliminating PCN emissions during secondary copper production.

Characterization of PCDD/Fs and dioxin-like PCBs in flue gas from thermal industrial processes in Vietnam: A comprehensive investigation on emission profiles and levels

The emission profiles and levels of unintentionally produced persistent organic pollutants (U-POPs) comprising polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) were comprehensively investigated in flue gas released from 20 facilities belonging to 11 thermal industrial processes in Vietnam. Levels and patterns of PCDD/Fs and dl-PCBs in flue gas samples varied widely between sectors and different facilities in the same sector, suggesting different formation mechanisms involved. Flue gas concentrations of PCDD/Fs and dl-PCBs generally decreased in the order: industrial waste incinerator > secondary zinc production > coal fired craft boiler > coal fired power plant ≈ medical waste incinerator > steel production ≈ cement production > secondary copper production > coal fired industrial boiler > secondary tin production ≈ municipal waste incinerator. Results obtained from diagnostic ratio and fingerprint analysis have revealed that the stack emissions of PCDD/Fs and dl-PCBs were probably attributed to the de novo formation and incomplete destruction of input materials containing technical PCB oils or paints. The average emission factors of PCDD/Fs and dl-PCBs ranged from 0.011 to 374 μg WHO-TEQ tonne−1 for the studied facilities. A total emission amount of 4.89–11.4 g WHO-TEQ year−1 was estimated for the 20 facilities investigated in our study. This is the first comprehensive investigation on the unintentional emissions of PCDD/Fs and dl-PCBs from a wide range of industrial sectors in Vietnam.

Kinetics of pore formation and resulting properties of lightweight inorganic polymers

AbstractInorganic polymer (IP) foams could be used as an alternative to commonly available cellular concretes. To do so, however, it is crucial to understand how the foaming kinetics and the final foam properties can be controlled and tailored to delivered the desired performance. The research reported in this article investigates the influence of the SiO2/Na2O ratio of the activating solution, addition time of foaming agent, and temperature, on the reaction kinetics and final properties of a porous IP. The IPs were formed by activating fayalite slag, a by‐product of secondary copper production, with a sodium‐silicate solution. Foaming was achieved by introducing metallic Al into the formulation, oxidizing it in the alkaline environment, liberating H2 gas, and entrapping it. Reaction kinetics were assessed using isothermal calorimetry, rheology, and a dedicated setup to record the foaming. The mechanical and physical properties of the foam were assessed via compressive strength and water absorption measurements. Microstructural analysis was undertaken using electron microscopy and computed tomography. The results showed that by decreasing the SiO2/Na2O ratio and/or increasing the temperature, the reaction kinetics were accelerated. Regarding the properties, postponing the initiation of the foaming led to more uniform and smaller pores, resulting in an increased compressive strength‐to‐density ratio.

Selective reductive leaching of cobalt and lithium from industrially crushed waste Li-ion batteries in sulfuric acid system

Recycling of valuable metals from secondary resources such as waste Li-ion batteries (LIBs) has recently attracted significant attention due to the depletion of high-grade natural resources and increasing interest in the circular economy of metals. In this article, the sulfuric acid leaching of industrially produced waste LIBs scraps with 23.6% cobalt (Co), 3.6% lithium (Li) and 6.2% copper (Cu) was investigated. The industrially produced LIBs scraps were shown to provide higher Li and Co leaching extractions compared to dissolution of corresponding amount of pure LiCoO2. In addition, with the addition of ascorbic acid as reducing agent, copper extraction showed decrease, opposite to Co and Li. Based on this, we propose a new method for the selective leaching of battery metals Co and Li from the industrially crushed LIBs waste at high solid/liquid ratio (S/L) that leaves impurities like Cu in the solid residue. Using ascorbic acid (C6H8O6) as reductant, the optimum conditions for LIBs leaching were found to be T = 80 °C, t = 90 min, [H2SO4] = 2 M, [C6H8O6] = 0.11 M and S/L = 200 g/L. This resulted in leaching efficiencies of 95.7% for Li and 93.8% for Co, whereas in contrast, Cu extraction was only 0.7%. Consequently, the proposed leaching method produces a pregnant leach solution (PLS) with high Li (7.0 g/L) and Co (44.4 g/L) concentration as well as a leach residue rich in Cu (up to 12 wt%) that is suitable as a feed fraction for primary or secondary copper production.