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As the electrification sector expands rapidly, the demand for metals used in batteries is increasing significantly. New approaches for lithium-ion battery (LIB) recycling have to be investigated and new technologies developed in order to secure the future supply of battery metals (i.e., lithium, cobalt, nickel). In this work, the possibility of integrating LIB recycling with secondary copper smelting was further investigated. The time-dependent behavior of battery metals (Li, Co, Ni, Mn) in simulated secondary copper smelting conditions was investigated for the first time. In the study, copper alloy was used as a medium for collecting valuable metals and the distribution coefficients of these metals between copper alloy and slag were used for evaluating the recycling efficiencies. The determined distribution coefficients follow the order Ni >> Co >> Mn > Li throughout the time range investigated. In our study, the evolution of phases and their chemical composition were investigated in laboratory-scale experiments under reducing conditions of oxygen partial pressure p(O2) = 10−10 atm, at 1300 °C. The results showed that already after 1 h holding time, the major elements were in equilibrium. However, based on the microstructural observations and trace elements distributions, the required full equilibration time for the system was determined to be 16 h. [ABSTRACT FROM AUTHOR]

A mathematical modeling approach was used to test different design modifications in a flash smelting settler to reduce the copper losses in slag, which is economically disadvantageous for copper processing using the pyrometallurgical route. The main purpose of this study was to find ways to reduce copper losses in slag by improving the settling and coalescence of copper matte droplets, in particular, the smallest droplet sizes of ≤100 µm. These improvements inside the flash smelting (FS) settler were targeted through different settler design modifications. Three different design schemes were tested using the commercial computational fluid dynamics (CFD) software, Ansys Fluent. These settler design modification schemes included the impact of various baffle types, positioning, the height inside the settler, and settler bottom inclinations. Simulations were carried out with and without coalescence and the results were compared with normal settler design. The results revealed that the settling phenomenon and coalescence efficiency were improved significantly with these design modifications. It was concluded that a single baffle design was optimal for reducing copper losses and increasing coalescence efficiency instead of using multiple baffle arrangements. The top-mounted baffle outperformed the bottom-mounted baffle and inclined settler design. [ABSTRACT FROM AUTHOR]

Improving metal–slag separation in pyrometallurgical processes is increasingly important. Due to the harsh conditions, direct observations of the molten phases behavior in the settler of the Outotec Flash Smelting Furnace (FSF) are not possible and the ways to improve metal settling can only be studied by simulation and modeling. This study focuses on kinetics and mechanisms of the chemical reactions between matte droplets and slag, which were investigated in laboratory-scale heat-quench equipment at a typical smelting temperature of 1300°C as a function of time in both air and argon atmosphere. The reaction mechanism in the FSF settler was formulated and results in argon atmosphere also indicate that the oxidation of cuprous sulfide by ferric ions in the slag contributes strongly to the copper losses in the slag. [ABSTRACT FROM AUTHOR]

The distributions of precious metals (gold, silver, platinum, and palladium) between copper matte and silica-saturated FeOx-SiO2/FeOx-SiO2-Al2O3/FeOx-SiO2-Al2O3-CaO slags were investigated at 1300 °C and P SO 2 = 0.5 atm. The experiments were carried out in silica crucibles under flowing CO-CO2-SO2-Ar gas atmosphere. The concentrations of precious metals in matte and slag were analyzed by Electron Probe X-ray Microanalysis and Laser Ablation-High-Resolution Inductively Coupled Plasma-Mass Spectrometry, respectively. The precious metal concentrations in matte and slag, as well as the distribution coefficients of precious metals between matte and slag, were displayed as a function of matte grade. The present results obtained at P SO 2 of 0.5 atm were compared with previous results at P SO 2 of 0.1 atm for revealing the effects of P SO 2 and selected slag modifiers (CaO and Al2O3) on precious metal distributions at copper matte smelting conditions. The present results also contribute experimental thermodynamic data of precious metal distributions in pyrometallurgical reprocessing of electronic waste via copper smelting processes. [ABSTRACT FROM AUTHOR]

Cobalt is a critical, high-value metal used extensively in batteries and other sustainable technologies. To secure its supply in future, it is utmost important to recover cobalt efficiently from industrial wastes and recycled End-of-Life batteries. This study aims at finding ways to improve the reduction of cobalt as well as valuable metals nickel and copper in nickel slag cleaning furnace conditions by using both traditional fossil-based coke and a more sustainable option, low-CO2 footprint biochar, as reductants. A cobalt-rich fraction of battery scrap (25.5 wt% Co) was also used as a secondary feed. The experimental technique consisted of reduction experiments with different times at 1400 ffiC under inert atmosphere, quick quenching and Electron Probe X-ray Microanalysis. The use of biochar resulted in faster reaction kinetics in the reduction process, compared to coke. Moreover, the presence of battery scrap had a clear impact on the behavior and reduction kinetics of the elements and/or enhanced settling and separation of matte and slag. The addition of scrap increased notably the distribution coefficients of the valuable metals but consequently also the iron concentration in matte which is the thermodynamic constraint of the slag cleaning process. [ABSTRACT FROM AUTHOR]

Recycling metals from secondary materials and more complex ores has recently been attracting more attention, creating a need for more precise separation methods of different elements. This study proposed a sulfation-roasting method and designed thermodynamic conditions to selectively facilitate the formation of copper sulfate while separating iron as oxide. The roasting behaviors for chalcopyrite, copper slag, and pure copper compounds were investigated in a 0.5% SO2–0.5% O2–99% Ar atmosphere at 600°C. X-ray fluorescence spectroscopy, x-ray diffractometry, scanning electron microscopy, and energy dispersive x-ray spectrometry were used to characterize the raw materials and roasting products. The proposed methodology was confirmed for a complete separation of Cu from Fe, and, further, the sulfation-roasting mechanism of chalcopyrite was confirmed by thermodynamic calculations and experimental observations. These will provide a theoretical basis for copper recycling from both complex primary and secondary copper-bearing materials. [ABSTRACT FROM AUTHOR]

The effects of the amphoteric and basic oxides alumina and lime on the phase equilibria of copper matte and silica-saturated slags were investigated at 1300 °C and P SO 2 = 0.1 atm in a controlled CO-CO2-SO2-Ar gas atmosphere using a high-temperature isothermal equilibration technique followed by rapid quenching. The equilibrium phase compositions were obtained by Electron Probe X-ray Microanalysis. The relationship between the copper concentration in matte and the oxygen partial pressure, iron, and sulfur in matte was quantified. The pure iron-silicate slag exhibited the highest copper loss in slag, although the addition of alumina and lime decreased its value by approximately a quarter and a half, respectively, at a matte grade of 65 wt pct Cu. In contrast, copper and sulfur were highly distributed in the matte phase, and their deportment to the matte was favored by addition of alumina and lime. [ABSTRACT FROM AUTHOR]

In spite of significant economic value, the solubilities of the platinum group and precious metals in metallurgical copper smelting slags are not well known. Recent experimental information on iron-free and low-iron silicate melts indicates that the chemical solubility of platinum is very low, < 1 ppmw (part per million weight). In this study, the concentration of platinum in alumina spinel-saturated iron silicate slags in equilibrium with a solid iron-platinum alloy was measured as a function of oxygen partial pressure at 1300°C. The results were converted to unit activity of platinum by the thermodynamic properties of the iron-platinum alloy formed. This allowed the mechanism of dissolution of platinum in the slag and the forms of platinum species in alumina-rich iron silicate slags in copper scrap smelting and refining conditions to be obtained. Our findings explain some inconsistent results in the geochemical literature by proposing an anionic dissolution mechanism at low oxygen partial pressures in iron-containing silicate slags. [ABSTRACT FROM AUTHOR]

The thermal conductivity of various copper matte and fayalite slag was measured using laser flash analysis, a non-steady state measurement method. Industrial matte and slag samples were taken in such a way that their composition represented typical process conditions. Thermal conductivities for solid copper matte (average 64% Cu) were found to be from 1.2 W m−1 K−1 at 300°C to 2.1 W m−1 K−1 at 900°C. Because arsenic is one of the most important impurities in copper matte, its effect on thermal conductivity was investigated with As-doped matte samples up to 0.59% As. The results showed substantially lower thermal conductivity, between 0.5 W m−1 K−1 and 1.3 W m−1 K−1 at 300–900°C with low As matte, behavior that is analogous to that of a semiconductor. The data obtained showed that the thermal conductivity of copper matte increased linearly with temperature, but the gradient was small. The thermal conductivity of slags was found to be between 1.6 W m−1 K−1 and 1.9 W m−1 K−1, values that are consistent with earlier studies. [ABSTRACT FROM AUTHOR]

The distribution equilibria of silver, indium, gallium, and tin between a copper alloy and alumina-containing iron silicate slag have been measured experimentally at 1300°C. In reducing conditions, copper acts as a collector for gallium, but its distribution coefficient between metal and slag is always less than one. Indium will be almost completely oxidized to the slag in high oxygen partial pressures and reduced fully back to the copper alloy in the slag cleaning conditions, around pO2 ≈ 10−10 atm. The behavior of tin is similar to indium in low oxygen pressures, where copper alloy dissolves most tin from the slag (log10 Lm/s(Sn) ≈ 2). In high oxygen partial pressures, most tin was volatilized from the system, and tin concentrations were below the detection limit (0.02 wt-%), less than 0.005 wt-% in slag and less than 0.002–0.003 wt-% in the alloy. Up to 90% of its initial silver amount in the copper alloy was lost in the gas at pO2 > 10−6 atm and its concentration in copper was less than 0.1 wt-% [Ag]. The observations suggest that addition of lime to iron silicate slags with alumina, in reducing conditions below pO2 ≈ 10−7 atm at silica saturation, lowers slightly the metal-to-slag distribution coefficients. [ABSTRACT FROM AUTHOR]

Alumina is a common substance deporting in copper smelting slags when various secondary copper fractions, e.g. e-scrap or WEEE, are used as feedstock as such or along with primary sulphide concentrates. Properties of iron-silicate slags at high alumina concentrations, in the iron-alumina spinel saturation, have been studied at 1300 °C by a high temperature equilibration-quenching method combined with EPMA (electron probe microanalysis) phase composition data from the polished sections. The equilibrations were performed in fixed oxygen activity with platinum or palladium powder, which dissolved iron from the slag and generated a heterogeneous equilibrium system, characterised by the general equilibrium criterium in isothermal and isobaric conditions, as. μ alloy (Fe) = μ slag (Fe) = μ spinel (Fe). This criterium was used for measuring experimentally iron activities of molten silicate slags. The locations of the spinel-liquid slag tie-lines were also determined in the oxygen partial pressure range of 10−6–10−10 atm. A comparison with the recent critical thermodynamic assessments of the Fe–O–Al 2 O 3 system indicates that the iron-alumina spinel-corundum phase boundary in silica-containing systems as a function of oxygen partial pressure is too steep and thus the assessed databases do not match with the experimental data of this study. The liquid slag domain from silica to iron oxide saturation is also smaller than expected earlier, as the spinel primary phase boundary locates at higher silica concentrations than e.g. obtained in the assessments of the Mtox database. • New, experimentally measured data regarding iron activity in Fe–Pt and Fe–Pd alloys was obtained. • The obtained iron activity values are in reasonable agreement with the assessed values in Mtox database. • Clear differences were observed between the measured spinel-alumina saturation boundary composition and the Mtox database. [ABSTRACT FROM AUTHOR]

Graphical abstract The use of methane as reductant in the treatment of slag milling and flotation tailings allows a low temperature metallisation of the magnetite (Fe 3 O 4) phase, precipitated from the copper smelting and converting slags during their cooling and solidification. Highlights • A new concept for cleaning copper slag flotation tailings. • Low temperature metallisation of iron volatilises harmful impurities from the slag. • Methane can metallize the magnetite precipitates from fayalite slags at low temperatures. Abstract Tailings from an industrial copper slag cleaning milling and flotation circuit have been pre-reduced at low temperatures, well below its melting point, using CH 4 -H 2 -Ar mixtures with the aim of metallizing its iron oxide component to metallic iron. The treatment carried out at 700–900 °C, with a duration of up to 90 min, indicated a complete transformation of magnetite within the first 30 min of the process. At the same time, significant fractions of its harmful impurities, antimony, arsenic, bismuth, lead and zinc, present as oxides in the slag were reduced from magnetite and the glassy inter-granular phase, and removed from the slag as flue dust in the process off-gas. The obtained fine slag powder with low impurity contents can be melted after the pre-reduction to synthetic rock or to fast cooled slag granules for further use. [ABSTRACT FROM AUTHOR]

The increasing concentrations of metallic Al or Al 2 O 3 in secondary copper resources like electronic wastes motivate research into the slag chemistry of high-Al 2 O 3 iron silicate slags for optimizing the industrial smelting process. In this study, the effect of Al 2 O 3 in slag on the phase equilibria of the FeO x -SiO 2 -Al 2 O 3 slag system was experimentally investigated at 1200 °C and p O 2 of 10−8.6 atm. The high-temperature experiments were undertaken in silica and spinel crucibles in a controlled CO–CO 2 gas atmosphere, followed by rapid quenching and Electron Probe Microanalysis. The equilibrium compositions of liquid slags in the tridymite primary phase field, spinel primary phase field, and the three-phase invariant point were determined. The 1200 °C isothermal section was constructed for the FeO x -SiO 2 -Al 2 O 3 system, and the results showed that Al 2 O 3 can dissolve in the liquid slags to a maximum concentration of 17 wt%. The present experimental results were compared with the predictions by MTDATA and FactSage. It was found that the present experimentally determined liquid domain agreed well with the calculations by FactSage except the invariant point. However, the present isotherm in the spinel primary phase field of spinel displayed lower Al 2 O 3 concentrations. The present results help regulating fluxing strategies of FeO x -SiO 2 -Al 2 O 3 slags and optimizing smelting operations of recycling high-alumina concentration copper resources. • The effect of Al 2 O 3 on the phase equilibria of iron silicate slags was experimentally determined. • The 1200 °C isotherm at p O 2 of 10−8.6 atm was constructed for the FeO x -SiO 2 -Al 2 O 3 system. [ABSTRACT FROM AUTHOR]

The equilibrium phase relations between metallic copper alloys and magnetite/wüstite-saturated iron silicate slags were investigated at 1200–1300 °C and P O2 of 10−10 to 10−6.5 atm. The experiments involved high-temperature equilibration of samples in a controlled CO–CO 2 atmosphere, followed by rapid drop quenching and direct measurement of the phase composition using the electron probe microanalysis technique. The equilibrium compositions for the metal and slag phase at different temperatures were displayed as a function of P O2. The present experimental results were compared with data from the literature as well as the thermodynamic assessment using MTDATA thermodynamic software. The present results contribute to the improvement of copper matte and black copper converting and slag cleaning processes. • Phase equilibria of copper alloys and FeO X -saturated iron silicate slags were experimentally and computationally investigated. • Iron concentration in alloy decreased with increasing P O 2 and lowering temperature. • Copper dissolution in slags increased with increasing P O 2 and decreasing temperature. • The experimentally measured copper concentration in magnetite and iron concentration in alloy fitted well with the calculations by MTDATA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Experimental study on recycling WEEE through copper smelting. • Ag can be effectively recovered into copper alloy at all conditions. • Co and Ni favored the solid phases compared to their dissolution in slags. • Ni and Sn were concentrated in copper alloy at lower P O2 but in slag at higher P O2. • Higher temperatures and lower P O2 favor the deportment of trace elements into the copper alloy. Recycling of waste electrical and electronic equipment (WEEE) is attracting increasing attention, due to the presence of valuable metals and the risk of environmental emissions associated with WEEE disposal. In this study, the distributions of trace elements (Ag, Ni, Co, and Sn) between copper alloy and magnetite/wüstite-saturated iron silicate slags were investigated at 1200–1300 °C and P O2 of 10-10-10-6.5 atm, simulating the conditions of WEEE reprocessing through secondary copper smelting and converting. The high-temperature isothermal equilibration experiments were conducted in synthesized magnetite/wüstite crucibles under controlled CO-CO 2 atmospheres followed by quenching in an ice-water mixture. The phase compositions and concentrations of the trace elements in copper alloy, magnetite/wüstite, and slag were determined by Electron Probe X-ray Microanalysis and Laser Ablation-High-Resolution Inductively Coupled Plasma-Mass Spectrometry. The distribution coefficients of all investigated trace elements between copper alloy and slag increased with decreasing oxygen partial pressure and increasing temperature. Ag distributed strongly into the copper alloy at all conditions, whereas Co mainly deported into the slag phase. Ni and Sn were concentrated in the alloy at lower P O2 and in the slag at higher P O2. Varying concentrations of Ni, Co, and Sn were also dissolved into the solid magnetite/wüstite phase. [ABSTRACT FROM AUTHOR]

A potential industrial waste-waste co-treatment process was proposed and verified for the recovery of the valuable metals Co, Ni, and Cu from copper smelting slag by utilizing high temperature SO 2 off-gas. Sulfation roasting followed by water leaching under designed thermodynamic conditions was conducted to facilitate the selective formation of Co, Ni, and Cu sulfates while separating iron as oxide. Several parameters were studied such as roasting temperature, roasting time, the addition of Na 2 SO 4 , and leaching agent. Under the optimized sulfation roasting conditions (Gas flow: 500 mL/min, 5% SO 2 + 20% O 2 + 75% Ar; Roasting temperature: 650 °C; Roasting time: 4 h; Addition of Na 2 SO 4 : 30%) followed by water leaching (Leaching temperature: 80 °C; Leaching time: 5 h; solid to liquid ratio: 0.05 g/mL), the extraction yields of Ni, Co, and Cu were shown to reach 95.8% and 91.8%, 81.6%, respectively. Furthermore, the sulfation roasting – water leaching process was confirmed on lab-scale as a feasible and efficient way to recover valuable metals and the mechanism was determined and verified from the microstructural evolution. Finally, a potential environmentally friendly industrial process in terms of the energy flow and material flow was presented based on preliminary assessments for environmental benefits, economic benefits, and heat recovery. [Display omitted] • An industrial waste-waste co-treatment process was proposed to recover Co, Ni, and Cu from copper smelting slag. • Reaction mechanism of the proposed sulfation roasting by water leaching process was experimentally defined and verified. • The extraction yields of Ni, Co, and Cu can reach 95.8% and 91.8%, 81.6%, respectively under the optimized condition. • A potential environmentally friendly industrial process referred to the energy flow and material flow was presented. [ABSTRACT FROM AUTHOR]

• Pyrometallurgical recycling of Waste printed circuit boards is assessed. • Reaction mechanisms and distribution of WPCB impurity elements Sb, As and Bi. • Kinetic data of these elements in WPCB recycling were calculated. • WPCB recycling in copper flash smelting process. Feeding Waste Printed Circuit Boards (WPCBs) into existing pyrometallurgical processes is developing as an easy-to-adapt and efficient way to recycle them. To fulfill sustainability and circular economy targets, kinetics and distributions are the key factors when recovering metals and trace elements from WPCBs. We investigated the reaction mechanisms and distribution behavior of impurity elements Sb, As and Bi between copper matte and slag at a typical smelting temperature of 1300 °C both in air and argon atmospheres. Laboratory-scale heat-quench experiments indicated that vaporization can effectively eliminate arsenic in the matte phase, but not antimony or bismuth either in air or in an argon atmosphere. Sufficient contact time between the gas and matte phase is also needed to transfer the trace elements into gas and slag. In this work, kinetic data and distribution ratios of these impurity elements in the matte and slag phase were calculated. They can be used in process development for WPCB recycling and, equally, when using complex copper concentrates with high As, Sb, and Bi contents. The results also complement CFD models to simulate flash smelting processes more precisely. [ABSTRACT FROM AUTHOR]