Search Results (279)

Lead-bearing dusts from metallurgical processes are hazardous secondary resources due to their complex composition and toxicity. At the same time, their high lead content makes them a promising feedstock for resource recovery. This study proposes an energy-efficient electrosmelting approach based on the partial substitution of sodium carbonate with calcium-rich industrial waste (sugar-industry defecate). Thermodynamic analysis and equilibrium modeling of the Pb–Sb–Fe–Na–Ca–Si–S–Cl–As system were performed in the temperature range of 200–1200 °C using Outotec HSC Chemistry. The results indicate that under equilibrium conditions approximately 90–95% of lead is concentrated in the metallic phase (~56 kg from ~60 kg in the feed), while antimony is co-recovered (~1.9–2.0 kg). The slag is dominated by calcium silicates, primarily Ca₂SiO₄, confirming the important role of CaO in slag formation and impurity fixation. Chlorine is predominantly bound as NaCl and partially as CaCl₂, while sulfur is distributed between Na₂S and Na₂SO₄. A significant portion of arsenic is predicted to be retained in the slag as calcium and sodium arsenates (Ca₃(AsO₄)₂ and Na₃AsO₄), whereas its volatilization is thermodynamically negligible under equilibrium conditions. Preliminary experimental results are generally consistent with the thermodynamic predictions and confirm the feasibility of partially replacing Na₂CO₃ with sugar-industry defecate. The proposed approach contributes to reducing the consumption of conventional fluxes and promotes the utilization of industrial waste within a circular-economy framework. Full article

The present study investigates the possibility of selective iron reduction from the Keregetas iron–manganese ore deposit (Kazakhstan) using hydrogen, followed by the separation of iron- and manganese-containing phases. The relevance of the research is associated with the need to develop environmentally sustainable processing technologies for low-grade iron–manganese ores under the conditions of metallurgical industry decarbonization. Experimental studies were carried out at temperatures of 800–900 °C in a high-purity hydrogen atmosphere, followed by magnetic separation and liquid-phase separation of the reduction products. The phase and chemical compositions of the samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). It was established that during the reduction process, iron oxides were predominantly transformed into the metallic state with the formation of α-Fe, whereas manganese oxides were mainly reduced to MnO and Mn₃O₄. Magnetic separation demonstrated limited selectivity due to the simultaneous transfer of iron-containing and manganese-containing phases into the magnetic fraction. At the same time, liquid-phase separation of the pre-reduced material at 1650 °C ensured effective separation of metallic and slag phases, with manganese concentrated in the slag and minimal losses in the metallic product. A technological flowsheet for the processing of iron–manganese ores is proposed, including hydrogen reduction, magnetic separation, and subsequent high-temperature phase separation. The obtained results demonstrate the prospects of hydrogen metallurgy for the development of low-carbon technologies for the integrated processing of iron–manganese raw materials. Full article

The growing accumulation of industrial waste and the depletion of natural mineral resources underscore the need for sustainable approaches to producing ceramic and construction materials. Among the most promising secondary raw materials are coal combustion by-products and metallurgical slags, which are suitable for ceramic applications. This review summarizes recent advances in the use of coal ash, blast furnace and steelmaking slags, together with clay-based raw materials, for the fabrication of ceramic and composite materials. Special attention is given to the physicochemical properties of technogenic raw materials and their effects on sintering, porosity, densification, mechanical strength, and thermal stability. Modern processing methods, including pressing and high-temperature firing, are also discussed. The influence of key technological parameters, such as oxide composition, particle size distribution, firing temperature, and activation conditions, is analyzed. In addition, the review examines major challenges related to raw material heterogeneity, structural instability, thermal stress development, cracking, free CaO reactivity, and environmental risks associated with heavy metal leaching. Recent studies show that incorporating industrial waste into ceramic systems reduces waste disposal, natural resource consumption, energy use, and CO₂ emissions, while promoting sustainable and resource-efficient technologies. Ash- and slag-based ceramics therefore remain highly promising materials for construction applications. Full article

This paper examines a resource-saving technology for ferrosilicon smelting using industrial waste, specifically aluminum slag and aspiration dust from ferroalloy production. A technological approach is proposed based on the preliminary pelletization of finely dispersed aluminum slag to improve the physicochemical properties of the charge materials and ensure their efficient use in the metallurgical process. Pellets were produced by granulation in a disk granulator using a lignosulfonate binder, followed by drying and high-temperature firing in the temperature range of 600–800 °C. Microstructural and energy-dispersive analysis revealed the formation of a stable aluminosilicate matrix, represented predominantly by mullite-like phases, ferrosilicate inclusions, and calcium–magnesium silicates. The formation of these phases contributes to the strengthening of the pellet structure and the formation of intergranular bonds during heat treatment. Experimental ferrosilicon smelting was conducted in a laboratory ore-thermal electric arc furnace. The results demonstrated a stable electrothermal smelting regime, satisfactory charge layer gas permeability, and effective reduction processes. The resulting alloy corresponds to FS-45 ferrosilicon grade with a silicon content of approximately 48%. It was established that aluminum slag-based pellets actively participate in the formation of an aluminosilicate slag system of the SiO₂-Al₂O₃-CaO-MgO type, ensuring favorable slag physicochemical properties and efficient separation of the metallic and slag phases. The proposed approach enables the incorporation of industrial waste into metallurgical production, reducing the environmental impact, and increasing the resource efficiency of silicon ferroalloy production processes. Full article

The article presents the results of experimental studies on the possibility of predicting the efficiency of CO₂ mineralization using metallurgical wastes (MWs) from the perspective of chemical thermodynamics and on identifying, accordingly, promising MWs for the production of construction materials and products. The study examined MWs from major Russian iron and steel producers, namely: blast furnace, electric steelmaking, ferroalloy, converter steelmaking slag, as well as nepheline slag, a by-product of nepheline ore processing for alumina. The CO₂ binding capacity of MWs was determined using experimental samples fabricated by semi-dry pressing of MW powders, followed by curing them in a gas atmosphere with an CO₂ concentration of 80% vol. It was found that the investigated MWs are capable of absorbing and binding CO₂, thereby improving their physical and mechanical properties. Experimental samples made from nepheline slag bind 11.3 to 12.0 wt.% of CO₂; samples from steelmaking slags: up to 9 wt.% or more; and samples from blast furnace dump slag: approximately 5.5 wt.% At the same time, the compressive strength of samples from steelmaking slags exceeds 100 MPa, that of samples from nepheline slag approaches 80 MPa, and that of samples from blast furnace dump slag exceeds 50 MPa. It has been established that predicting the efficiency of CO₂ mineralization by metallurgical wastes based solely on chemical thermodynamics is not entirely accurate. To develop a preliminary forecasting model for the carbonate hardening potential of various MWs, further studies are needed to identify additional key factors influencing the carbonate hardening process of MWs. Full article

Efficient recovery of critical raw materials such as lithium from metallurgical slags requires optimized liberation of target phases during comminution. To determine effective mechanical process parameters for target phase recovery, an in-depth understanding of the characteristics of slag particles is crucial. For this purpose, modern tomography techniques, such as computed tomography (CT), can provide high-resolution 3D images of micrometer-sized slag particles. However, analysis of such CT images poses challenges, such as insufficient grayscale contrast between mineral phases and partial-volume effects. This paper presents a scalable workflow for accurate phase- and particle-wise 3D characterization of particle systems by correlating 3D CT images with 2D mineral maps. For this purpose, high-resolution scanning electron microscopy (SEM) slices are registered in 3D CT images and used as ground truth to train 3D convolutional neural networks (CNNs) for the segmentation of individual particles and mineral phases. This approach addresses the principal challenges of obtaining CT-based mineralogical characterizations, allowing for the particle-wise 3D characterization of complex slag systems with minimum manual labeling effort. The trained CNNs are then applied to CT images of particle systems with different particle sizes (from 63 μm to 100 μm and from 100 μm to 250 μm) of a lithium-bearing slag with LiAlO₂ as the target phase. Although virtual cross-sections of the predicted 3D segmentations show excellent agreement with mineral liberation obtained from 2D validation SEM-EDS data, the derived 3D mineral liberation statistics differ significantly from 2D estimates. In particular, our results show that the 2D analyses significantly overestimate mineral liberation compared to the 3D characterization. By addressing this stereological bias, the correlative 3D characterization workflow provides essential insights required to tailor pyrometallurgical and mechanical processing parameters to improve the recovery of raw materials. Full article

Vanadium extraction tailings, as a highly alkaline and hazardous solid waste, pose not only serious environmental risks but also severely hinder the large-scale recycling of secondary iron resources. This study proposes an innovative process of “mild alkali leaching for vanadium extraction coupled with deep calcification and dealkali removal”. The vanadium extraction slag from a steel plant in China was used as a raw material to carry out the experimental and pilot study of alkali leaching of vanadium and calcification dealkalization. Experimental results show that under the conditions of 120 °C, 1% NaOH solution, liquid-solid ratio of 4:1 to 6:1, and reaction time of 1 h, vanadium leaching rate can reach 50%, which can be effectively used as a high-value-added economic hedge. Subsequently, under the conditions of 200 °C, calcium oxide concentration of 19.29%, stirring speed of 800 rpm, liquid-solid ratio of 4:1, and reaction time of 1 h, the Na₂O content in the tailings was successfully reduced to below 1%. A large number of tailings can be converted into high-quality secondary iron ore resources, which are suitable for subsequent iron-bearing briquette preparation and blast furnace ironmaking. Furthermore, pilot-scale testing in a 200 L reactor verified the engineering scalability of this combined process, maintaining a vanadium extraction rate of over 50% and an alkali removal rate of over 80%. This study provides a robust, scalable, and highly profitable pathway for the comprehensive utilization of high-alkali metallurgical solid waste. Full article

Mining activities generate large volumes of waste that pose both environmental liabilities and potential secondary resource value. A significant fraction of these materials still contains recoverable copper, making leaching a promising strategy for reprocessing and valorization, given the natural decline in ore grade. This study presents a PRISMA-based systematic review of recent literature on leaching technologies applied to mining waste, with emphasis on technical performance, environmental implications, and economic feasibility. The reviewed residues include tailings, slags, copper smelter dusts, sludges, waste rock, leaching residues, and other secondary mining and metallurgical wastes. The main leaching routes identified were acidic, biological, alkaline, and hybrid systems, including conventional H₂SO₄ leaching, pressure oxidative leaching, chloride-based systems, glycine- and ammonia-based alkaline media, organic acids, deep eutectic solvents, and biologically mediated processes. Reported Cu recoveries ranged from low values in refractory systems to near-complete extraction under optimized conditions. Overall, copper recovery was controlled primarily by the mineralogical occurrence of Cu rather than by leaching category alone. In contrast, the highest recoveries were generally associated with intensified conditions capable of overcoming sulfide- and silicate-related constraints. Environmental and circular economy benefits were frequently claimed but less often demonstrated through direct evidence, while economic assessment remained limited. Future research should better integrate mineralogical interpretation, environmental verification, and economic feasibility. Full article

Flotation tailings and metallurgical slags from mining often contain toxic Pb, Cd, and Zn. In this study, we evaluated the in situ immobilization of Pb, Cd, and Zn in a Pb–Zn flotation tailing and a smelting slag by adding representative amendments: phosphate-based (ammonium phosphate, phosphoric acid, glassy fertiliser), cementitious (Portland cement), and iron-based (bog iron ore) materials at 1–10% (w/w). Treated samples underwent EPA-TCLP and pH-dependent leaching tests (pH 3–10), with Pb, Cd, and Zn measured by atomic absorption spectroscopy. The untreated tailing leached hazardous Pb (~60 mg/L) and elevated levels of Cd (~0.7 mg/L) and Zn (~53 mg/L), whereas the untreated slag leached negligible metal concentrations. All amendments reduced metal release in a dose-dependent manner. Phosphate amendments were most effective (e.g., 10% H₃PO₄ cut tailing Pb by 80%, Cd by 60%, and Zn by 30%), while cement and iron additions had much weaker effects. Solid-phase XRD and SEM-EDS analyses indicated the formation of stable calcium–phosphate minerals on sulfide surfaces after phosphate treatment. These findings suggest that low-cost phosphate additives (~5–10%) can substantially immobilize Pb, Cd, and Zn in such wastes. However, under strongly acidic conditions (pH < 3), some remobilization occurred, highlighting the need for further validation. This work provides practical guidance for waste managers on selecting in situ stabilization strategies for Pb–Zn mine wastes. Full article

This study evaluates the feasibility of using waste Bakelite thermoset as a slag foaming and iron oxide reduction agent in electric arc furnace (EAF) steelmaking. Bakelite was blended with metallurgical coke at three ratios (10–30 wt% Bakelite), designated as Blend#1 to Blend#3. All carbon samples were heat-treated at 1000 °C under an argon atmosphere to produce char and were subsequently assessed for carbon–slag interactions at 1550 °C, with emphasis on slag foaming behavior and FeO reduction. The incorporation of Bakelite increased the total carbon content and significantly altered coke ash chemistry, marked by reduced SiO₂ and Al₂O₃ and increased CaO contents. Structural analysis revealed enhanced carbon graphitization with increasing Bakelite proportion. Among all samples, Blend#3 exhibited the most stable and pronounced slag foaming, achieving a maximum volume ratio of approximately 1.7 and forming uniformly distributed, multi-sized gas bubbles within the slag. FeO reduction improved with Bakelite addition, with metallization degrees of 77.30, 81.65, 80.56, and 84.41% for coke, Blend#1, Blend#2, and Blend#3, respectively. Blend#3 produced the lowest total gas emission (186,000 ppm), approximately 30% lower than that of pure coke. These findings demonstrate that waste Bakelite thermoset is an effective low-carbon alternative carbon source for EAF steelmaking, enhancing FeO reduction, slag foaming stability, and overall environmental performance. Full article

This study investigates the agglomeration of chromium-containing dust from ferroalloy production using rigid vacuum extrusion. Direct utilization of fine technogenic materials in submerged arc furnaces is limited due to poor gas permeability, increased dust generation, and unstable smelting conditions. The aim of this work was to compare bentonite and polymer binders in brex production and evaluate their metallurgical applicability. Chromium-containing dust from the gas-cleaning system of the Aktobe Ferroalloy Plant (TNC Kazchrome JSC, ERG) was characterized using chemical analysis and SEM/EDS methods. The material exhibited a heterogeneous structure composed mainly of chromium-containing spinel, silicate, and oxide phases. Pilot-industrial extrusion tests were performed using J.C. Steele & Sons equipment with bentonite (10 wt.%) and polymer binder TD 021.005.BS (2.5 wt.%). The polymer binder provided improved brex geometry and significantly higher mechanical strength, achieving impact strength values up to 89.5% after curing. SEM/EDS analysis of the obtained brexes confirmed the formation of a dense agglomerated structure with uniform distribution of chromium-containing phases. Thermodynamic modeling using FactSage 8.4 showed that brex addition does not significantly affect slag composition, phase equilibria, or metal quality during high-carbon ferrochrome smelting. The results demonstrate the feasibility of polymer binders for efficient recycling of chromium-containing technogenic wastes by rigid vacuum extrusion. Full article

Under conditions of depletion of natural resources and increasing volumes of techno-genic waste from metallurgical and alumina production, the development of technologies for the integrated processing of sludges with the extraction of valuable components becomes highly relevant. This study proposes a method for the combined processing of red mud and dump sludge to obtain pig iron, a rare earth element concentrate, and titanium dioxide. The reduction smelting of a briquetted charge composed of sludge mixtures was carried out in a muffle furnace at 1350–1400 °C with the addition of a reducing agent. Magnetic separation of cast iron slag made it possible to reduce the iron content in the non-magnetic fraction and increase the concentration of REEs. As a result of nitric acid leaching of the non-magnetic slag fraction, followed by neutralization and calcination of the titanium-containing precipitate, a rare earth element concentrate and titanium dioxide containing 96.5% TiO₂ were obtained. The developed method ensures the utilization of technogenic raw materials and contributes to the creation of an additional resource base for the production of strategically important materials. Full article

This study explores the use of metallurgical slag extracts as a liquid mineral fertilizer for maize cultivation. Slag samples were obtained from the former lead smelter in Shymkent and the Zhezkent Mining and Processing Plant. Elemental analysis identified the slag from the second storage area of the Shymkent smelter as the least contaminated with potentially toxic elements and enriched in macro- and micronutrients. Slag extraction was conducted via chemical leaching using potassium sulfate and ammonia solutions in a hydrogen peroxide medium, yielding Cu²⁺ and Zn²⁺ concentrations of 423.751 mg/L and 86.649 mg/L, respectively. The resulting extracts were diluted with distilled water at a ratio of 1:10 (potassium sulfate extract) and 1:200 (ammonia extract) and applied to assess early seed development and subsequent maize yield. Seed germination rates were comparable to those of the control group (100%). After 90 days of growth, maize plants treated with the ammonia-based extract showed positive effects on root system development, stem growth, and cob formation. The concentration of potentially toxic elements in the dry plant biomass remained within permissible limits. These findings demonstrate the potential for the safe agricultural use of these extracts while ensuring the rational utilization of industrial waste. Full article

Chromium slag, a chromium-bearing solid waste characterized by substantial environmental hazards yet with appreciable resource potential, has become a focal topic in solid-waste pollution control and the circular economy. Centered on the overarching logic of “evidence chain–system boundary–scalable and verifiable acceptance,” this review systematically synthesizes recovery technologies, industrial-scale utilization pathways, and the key challenges associated with the detoxification and resource utilization of chromium slag. From the perspective of recovery technologies, we examine pyrometallurgical and hydrometallurgical routes, solidification/stabilization (S/S), and bioelectrochemical coupling approaches, elucidating their fundamental principles, applicability boundaries, and critical nodes where environmental burdens may be transferred across media. We emphasize that process design should concurrently consider detoxification efficiency, resource recovery performance, and whole-process pollution control. Regarding utilization pathways, this review highlights three major routes with strong scale-up relevance—metallurgical process co-treatment (CAP–sintering–blast furnace), bulk utilization in construction materials, and high-value utilization—and analyzes their industrial potential and engineering constraints. Particular attention is given to the lack of long-term leaching and durability evidence, which represents a central bottleneck limiting product-side credibility. Furthermore, we discuss cross-cutting challenges including the long-term stabilization of Cr(VI), the verifiability of “green utilization” concepts, cost and economic feasibility, and standardized acceptance criteria. We propose that future research should shift from single-process optimization toward multi-objective, system-level evaluation, and establish a full-chain evidence system covering “speciation/mineral phases–process mechanisms–environmental behavior–risk assessment–engineering scale-up–standardized acceptance.” This review aims to provide a systematic analytical framework and practical reference for improving comparability across resource-utilization technologies and supporting engineering decision-making for chromium slag management. Full article

Copper slag was used as a raw material to prepare lithium ferrite by the solid-state reaction method at different Li:Fe molar ratios. The obtained materials were characterized by XRD, SEM, and N₂ adsorption–desorption, and their CO₂ capture behavior was evaluated using thermogravimetric and temperature-programmed techniques. A 7:1 Li:Fe molar ratio allowed to obtain Li₅FeO₄, as well as Li₄SiO₄, due to the high silicon content in the slag. CO₂ sorption tests showed that, as temperature increases, CO₂ capture increases up to 675 °C. Slag-ferrite achieved a maximum CO₂ capture of 20 wt% at 675 °C (P_CO2 = 0.2), equivalent to 62.5% of the CO₂ sorption of reagent-grade ferrite (32 wt%). Kinetic analysis of CO₂ capture using the Avrami–Erofeev model indicated that bulk diffusion is the rate-controlling step. These results provide quantitative evidence on the use of copper slag in the preparation of lithium ferrites, with potential application in a high-temperature CO₂ capture process. Full article