Pyrometallurgical copper extraction yields large slag volumes—typically 2.2 to 3.0 tons per ton of copper produced—underscoring the need for valorization strategies to improve resource efficiency. Utilizing these slags as supplementary cementitious materials (SCMs) offers a promising pathway. However, data on how composition influences the inherent reactivity of industrial slags remain scarce. Previous laboratory studies have shown that increasing CaO enhances slag performance as an SCM, but data on industrially CaO-modified slags remain limited. This study evaluates the inherent reactivity of industrial modified copper slags with 3.2–15.9 wt.% CaO. Electric smelting furnace slags were modified in a fuming furnace, tapped into a settling furnace, and water-granulated. Reactivity was assessed using the R³ isothermal calorimetry test after laboratory milling. X-ray diffraction (XRD) and scanning electron microscopy (SEM)–energy-dispersive x-ray spectroscopy (EDS) confirmed an amorphous structure with dispersed matte, speiss, and spinel phases. Increasing CaO depolymerized the silicate network, promoting dissolution and enhancing early-stage heat flow. When comparing fineness levels, the cumulative heat after 7 days correlated most strongly with specific surface area (R² = 0.92), confirming that fineness governs overall reactivity. Normalization of the cumulative heat for reactive oxides (SiO₂ and Al₂O₃) and specific surface area revealed that intrinsic reactivity increases with NBO/T ratio, demonstrating that a more depolymerized glass structure promotes chemical dissolution and higher reactivity. These findings demonstrate that industrial CaO modification enhances early hydration kinetics without reducing pozzolanic activity, confirming the suitability of CaO-modified copper slags as SCMs for cementitious systems.

To reduce the environmental impact of steel production, multiple European companies are planning a shift toward electric arc furnace (EAF) process using hydrogen-based direct-reduced iron (H₂-DRI) as a raw material. The changes in the process and the raw materials are reflected on the generated slags, and ideally the slag could be used as a supplementary cementitious material. However, original air-cooled EAF slag has poor cementitious properties, so an amorphous material must be generated by means of slag modification. In this study, an H2-DRI-based EAF slag was modified using mine tailings and rapidly cooled by water granulation. Combination of modification and partial reduction of iron oxides by carbon produced a highly amorphous material, which is promising for the valorization of the slag. Additionally, the possibility of using electron backscatter diffraction technique to quantify the amorphous phase content was studied and compared to conventional quantitative x-ray diffraction. While the obtained percentages differed depending on the method, the trend of increased amorphous content with increasing modification was clear with both methods.

The equilibrium phase relations and chromium partitioning in the Al2 O3 -SiO2 -MgO- CaO- CrOx system were investigated at 1600◦C and p O2 of 10− 10 atm. The high-temperature isothermal equilibration technique, followed by rapid quenching and direct phase composition analysis using electron probe microanalysis, was employed. Two-phase equilibria of liquid-corundum and liquid-spinel, as well as three-phase equilibria of liquid-cristobalite-corundum and liquid-spinel-corundum, were determined. To quantify the effects of Al2 O3 level and (MgO + CaO) on the primary phase fields of Cr-rich components, the CrOx -SiO2 - (MgO + CaO) pseudo-ternary phase diagrams were constructed at Al2 O3 = 7, 11, and 17 wt% based on the experimentally determined liquid and solid compositions. It was found that the Al2 O3 content had no significant effect on either the spinel primary phase field or the liquid-spinel-corundum three-phase equilibrium region. However, with increasing Al2 O3 content from 7 wt% to 17 wt%, the isotherm for the corundum primary phase field shifted toward the CrOx -SiO2 side at higher CrOx contents, thereby enlarging the liquid region. Chromium incorporation in the spinel decreased as (MgO + CaO), and the Al2 O3 content of the liquid increased. Overall, chromium partitioned preferentially into spinel and corundum relative to the liquid, whereas the spinel-liquid partitioning was more sensitive to Al2 O3 level and (MgO + CaO) in the liquid, consistent with decreasing chromium incorporation in Mg(Cr,Al)2 O4 spinel as the melt became more basic and Al-rich, due to the enhanced Al for Cr substitution coupled with reduced dissolved Cr availability.

The transition of the ore-based steel industry will increase the global volumes of electric arc furnace (EAF) slag and introduce new components inherently associated with iron ore. For example, vanadium is expected to partition to the slag, and its implications on downstream slag valorization must be considered. Therefore, the present study addressed the effect of VOx concentration on characteristics relevant to valorization as a supplementary cementitious material (SCM). A synthetic water-granulated CaO‒SiO2‒MgO‒Al2O3‒FeOx‒VOx slag system was systematically varied in VOx. By incorporating VOx, the saturation of the divalent metal oxide solid solution (RO-phase) and crystallization of spinel were promoted. Furthermore, dicalcium silicate crystallized at higher temperatures, which suggested an overall greater tendency for crystallization with increasing VOx concentrations. The effect of adding VOx on the vitrified fraction of the slag was studied by Raman spectroscopy, indicating that vanadium was incorporated into network-forming structures, but still had a net depolymerizing effect. By standardized SCM reactivity testing, VOx concentration was found to improve the inherent reactivity of the slag, which was suggested to stem from the depolymerization and the fact that vanadium is not expected to introduce internal diffusion barriers upon slag particle dissolution. Consequently, incorporating VOx into future EAF slags should be further investigated for environmental aspects as the reactivity was not negatively affected.

The increasing use of lithium-ion batteries (LiBs) in electric vehicles and electronics has made efficient recycling essential for maintaining a reliable and affordable supply of critical metals. Thermal treatment of black mass (BM), the heterogeneous residue from spent LiBs, is a crucial step to improve downstream material separation and recovery. This study investigates the thermal behavior of LiBs BM by analyzing the thermal behavior of its components when heated to 600 °C in an inert (N2) atmosphere or in a mixture of 90 vol % N2 and 10 vol % H2. Thermogravimetric analysis (TGA) was conducted at a heating rate of 10 °C/min with an isothermal hold of 1 h, and coupled with quadrupole mass spectrometry (QMS). The analysis was performed on graphite, activated carbon, lithium hexafluorophosphate (LiPF6), polyvinylidene fluoride (PVDF), synthetic black mass, and lithium nickel manganese cobalt oxide (NMC) industrial BM. Equilibrium calculations conducted in FactSage 8.3 were used to describe and understand the experimental findings. The TGA results indicate that in 100 vol % N2, graphite exhibited the lowest weight loss of 0.1 wt %, followed by activated carbon at 2.9 wt %, PVDF at 56 wt %, and LiPF6 at 81 wt %. Synthetic black mass had a weight loss of 3.4 wt %, while industrial black mass had 1.0 wt %. In 90 vol % N2/10 vol % H2, LiPF6 and PVDF experienced weight losses of 79 and 64 wt %, respectively. Synthetic BM had a weight loss of 15.1 wt %, and industrial BM 15.6 wt % due to enhanced reduction of metal oxides in the presence of hydrogen. 

The amount of waste Li-Ion Batteries (LIBs) is significantly growing. Therefore, scholars and industries are exploring efficient ways to recover their valuable elements. Meanwhile, steel production generates Fe-rich slag, which is often sold for construction purposes without fully utilizing its potential metal content. Reusing this slag in LIB recycling allows simultaneous recovery of valuable elements from both waste LIBs and steel slag. This study investigates the pyrometallurgical recycling of Black Mass (BM) from a mixture of spent LIBs in the presence of Fe-rich slag (set based on Electric Arc Furnace (EAF) slag), with a focus on the evaporation of Li and F, the critical volatile elements in the BM, at 1500 °C. The effects of basicity (B2), MgO content, and flux amount on Li and F evaporation were studied using a central composite experimental design, showing that while the effects of MgO content and flux amount were insignificant, B2 had a linear effect on Li and a quadratic effect on F evaporation. Thermodynamic and viscosity calculations suggest that higher B2 improves ion mobility, facilitating the evaporation mechanism. However, for F, its dual role at different B2 levels leads to an evaporation trend different from that of Li. Keeping B2 within a midrange seems to balance Li evaporation efficiency while limiting F evaporation.

Pyrometallurgical copper extraction generates between 2.2 and 3.0 tons of slag per ton of copper. Copper smelting slag usually contains between 1 and 2 wt pct Cu, resulting in a substantial amount. Effective slag cleaning is critical to enhance copper recovery, often achieved through settling where entrained droplets separate from the slag. Controlling slag viscosity is vital, directly influencing the settling rate and overall efficiency. The literature has limited data on the correlation between viscosity, ionic structure, and the molar ratio of (Al2O3 + SiO2)/MO (MO represents basic oxides) of iron silicate melts. This study investigates how FeO/SiO2 ratio (1.08 and 1.25 at pct/at pct), CaO content (1.2 and 12 at pct), and Al2O3 content (1.4 or 5 at pct) affect the viscosity and melt structure in a FeO–SiO2–Al2O3–CaO–MgO–Cr2O3 system. The study was done by synthesizing the melts, followed by water granulation. The ionic structure was analyzed using Raman spectroscopy, and the viscosity was measured using a high-temperature rheometer. The findings reveal a correlation between melt structure and viscosity, where the viscosity increased when the slag was more polymerized, having a higher content of SiO2 and Al2O3. The study offers insights for optimizing slag properties in industrial settings.

Pyrometallurgical extraction of copper generates an average of 2.2–3.0 tons of slag per ton of copper. With rising copper demand, future increases in slag volumes are expected, making the exploration of sustainable slag utilization essential. There are several applications for iron silicate slag. However, from a global perspective, a large amount of slag still ends up in landfills due to environmental concerns related to the potential weathering of metals present in the slag. This occurs despite results indicating that an improved slag-cleaning process makes iron silicate slag suitable for external applications. One potential application is utilizing iron silicate slag in the cement industry as a supplementary cementitious material (SCM). Given the wide range of ZnO content found in iron silicate slags worldwide, along with previous studies on Portland cement indicating that ZnO negatively affects the cement’s hydration process, there is a clear need for a structural investigation into how ZnO impacts the reactivity of iron silicate slag. This understanding is important for optimizing the use of iron silicate slag as an SCM. Therefore, this study covers a systematic investigation of the effect of ZnO on the inherent reactivity of iron silicate slag. Synthetic slags in the FeO–SiO2–CaO–Al2O3–MgO–ZnO system, with systematic variations in ZnO concentrations between 0 and 14.6 wt.%, were produced on a laboratory scale using water granulation. Results from isothermal calorimeter testing indicate that increasing ZnO concentrations decrease the slag’s inherent reactivity. These findings highlight the necessity of implementing a slag-cleaning process that minimizes zinc concentrations to facilitate the successful use of iron silicate slag as an SCM.

The increasing availability of spent lithium-ion batteries (LIBs), which are rich in valuable metals such as nickel (Ni), cobalt (Co), and lithium (Li), makes them important secondary sources for metal extraction. This study focused on the recovery of Li from a fue dust generated during pyrometallurgical processing of NMC 622 battery material, where Li was present as Li₂CO₃ and LiF along with various impurities. To selectively extract Li, the fue dust was subjected to leaching with carbonated and limewater under varying temperature and S/L (solid/liquid) ratio. The leachates and leach residues were analyzed to determine Li recovery, co-leached impurities, and to identify possible factors limiting recovery. Leaching with carbonated water at an S/L ratio of 0.05 g/ml, 50 °C and pH of 7.5 resulted in a 70% recovery of Li over 60 min of leaching time, which reduced at higher S/L ratio and temperature. In contrast, when leaching with limewater at 75 °C and S/L ratio of 0.05 g/ml, 77% Li recovery was achieved within 10 min. During these conditions, the pH reached 10. SEM and XRD analysis revealed a CaCO3 precipitate such as calcite, aragonite, and vaterite in varying proportions, causing surface passivation and inhibition of the leaching reaction. Leaching in limewater not only yielded higher Li recovery but also resulted in lower concentration of co-leached impurities (sodium, potassium, aluminum, and zinc), as compared to carbonated water leaching. However, the impurity levels remained high, requiring further purifcation and separation to produce battery-grade LiOH·H2O.

The effect of V2O3 on the viscosity of a calcium silicate melt-based system containing MgO and “FeO” was investigated and correlated with the melt composition using FactSage 8.2, SEM, and XRF. The viscosity was measured with incremental steps of 25 K from 1923 K to 1723 K in an argon atmosphere. The temperature-dependent viscosity was calculated for each slag composition using an Arrhenius-type equation. The results showed that the addition of 5.4 wt pct V₂O₃ decreased the viscosity of all measured slag systems. Viscosity is an important factor that influences the ability to create a foaming slag in the electric arc furnace (EAF). A synthetic slag with a composition close to an EAF slag was also measured with and without V₂O₃. Again, the addition of V₂O₃ decreased the viscosity but also decreased the saturation with magnesio-wüstite and decreased the temperature for formation of dicalcium silicate.