Iron Slag Research Articles

Hydrogen Reduction of Hazardous Bauxite Residue for Green Steel and Sustainable Alumina Production

Abstract This study introduces a novel approach in sustainable metallurgy for the efficient utilization and valorization of bauxite residue, aimed at producing sustainable alumina and green steel. The integrated process combines hydrogen reduction, alkaline leaching, and smelting of the leaching residue. Initially, the bauxite residue was pelletized with calcite and quicklime to create self-hardened pellets, leveraging the cementing effect of quicklime with water. These pellets underwent hydrogen reduction, achieving over 95% reduction, resulting in the formation of metallic iron and a leachable calcium aluminate phase for alumina recovery. The reduced pellets were then subjected to alkaline leaching, extracting 62% alumina. Subsequently, smelting at 1550 °C facilitated the near-complete separation of iron and calcium-rich slag. The process was analyzed using various analytical techniques, including X-ray diffraction, electron probe microanalysis, and inductively coupled plasma mass spectroscopy, complemented by thermodynamic calculations using FactSage 8.1 software. Iron oxide reduction to metallic iron was achieved at 1000 °C for 120 min, while sodium carbonate leaching effectively extracted alumina from the calcium aluminate slag. However, residual alumina was attributed to the formation of indissoluble gehlenite and a dense calcium carbonate layer that impeded leaching kinetics. Successful iron separation during smelting required temperatures above 1500 °C, though this process was challenged by the high viscosity of the oxide matrix and the purity of the iron. Graphical Abstract

The New Paradigm Caused by Regulation (EU) 2024/1252 on the Upcycling of Landfilled Ferrous Slags—Case Study: Iron and Steel Slag Dumps in Romania

Romania has some huge ferrous slag stockpiles that are secondary resources of minerals. Although a sizable portion of ferrous slags is recycled for use in building roads and other infrastructure, a sizable portion is still dumped. By November 2026, Member States must submit information on the quantity of critical raw materials (CRMs) in their secondary resources, as well as the quantification techniques employed, in accordance with Regulation (EU) 2024/1252. Therefore, the XRFS reliable measurements carried on ferrous slags were addressed to prevent dissipative loss of CRMs in cases where an improper slag recycling route is operated. The main novelty of this paper is the method of ensuring the reliability of the XRFS results based on weighted arithmetic mean and on the maximum likelihood approach. Secondly, the XRFS measurements carried on ferrous slags demonstrate that they contain CRMs like Ba, Sr, Y, etc.; however, below the minimum cut-off grade for CRMs, recovery XRFS cannot detect light CRMs. Our preliminary LIBS measurements on ferrous slags disclosed the presence of Li and Be. The drawbacks of the XRFS technique impose further research to develop an integrated XRFS, LIBS, and XRD procedure for comprehensive and trustworthy CRMs screening in extractive waste piles.

Assessing the Effects of Libyan Iron Slag on Self-Compacting Concrete Characteristics

The current study addresses the growing environmental issue of waste from blast high furnaces, particularly iron and steel plants in Libya. It investigates the fresh and mechanical properties of Self-Compacting Concrete (SCC) by substituting conventional aggregate with slag aggregate. The fresh properties of SCC were assessed using slump flow diameter, T50 flow time, J-ring, and L-box tests. Its mechanical properties were also evaluated, including compressive strength, flexural strength, splitting tensile strength, and Ultrasonic Pulse Velocity (UPV). Various replacement ratios were tested, 30%, 60%, and 100% for coarse aggregate, 10%, 20%, and 30% for fine aggregate, and combinations of coarse and fine aggregate at specified ratios. The results indicated that higher slag powder content slightly increased the setting times. The coarse slag aggregate proportions negatively impacted the filling ability, while fine aggregate proportions enhanced it. The passing ability decreased when 60% of coarse slag was used as a replacement, but it improved with a 100% coarse slag replacement. Interestingly, replacing 60% of coarse aggregate with slag enhanced compressive strength. Meanwhile, the best flexural and splitting tensile strengths were observed with 20%-30% replacements of both coarse and fine aggregates with slag. All slag aggregate mixtures were classified as of excellent quality based on UPV assessments, highlighting their potential as sustainable construction materials.

Machine learning for predicting strength properties of waste iron slag concrete.

This study investigates the utilization of waste iron slag (WIS) as a sustainable alternative in concrete production to reduce environmental impact and preserve natural resources. The experimental investigation of WIS-incorporated concrete focused on compressive and tensile strength with machine learning (ML) models for prediction. Among the tested ML algorithms, Decision Tree (DT) and XGBoost showed the highest accuracy (R2=0.95135) in predicting concrete strength properties, while models like SVM and Symbolic Regression underperformed. Experimental results indicate that up to 20% WIS replacement maintains adequate strength, whereas higher proportions reduce structural integrity. A ranking score index and cost analysis confirmed the technical and economic feasibility of using WIS in concrete. Cost analysis demonstrated substantial cost savings with 25% WIS incorporation, confirming its economic feasibility. Integrating experimental data with ML predictions highlights WIS's potential for sustainable concrete applications, enabling optimized mix designs and reduced reliance on physical testing. Future work should address limitations, including dataset expansion and the exploration of additional durability and mechanical properties to validate WIS's practicality in construction further.

ZERO CEMENT GEOPOLYMER CONCRETE AS AN ANTI-RADIATION MATERIAL WITH IRON SLAG AS A COARSE AGGREGATE

This research aims to analyze the use of iron slag as a substitute for coarse aggregate in geopolymer concrete as an anti-radiation material. In this program, 45 cylindrical 15 × 30 cm test objects were used. Treatment of the specimens was carried out by immersing them in a pool for 7 days, 14 days, and 28 days. Variations in iron slag in this study were taken at 0%, 20%, 25%, 30% and 35%. The radiation test is carried out by exposing the test object to X-rays, which is carried out in the Radiotherapy room at the Dharmais Cancer Hospital, Jakarta The results of radiation tests with a dose of 100 kV, geopolymer concrete with 35% iron slag was able to absorb 17.63% higher radiation than normal test objects without slag. Apart from that, the addition of iron slag with a content of 35% was able to reduce the reduction in compressive strength of concrete exposed to radiation. It was recorded that with 35% slag, there was a reduction in compressive strength of 5.09% after radiation. Based on its specific gravity, geopolymer concrete with 35% iron slag produces a specific gravity of up to 3,162.34 kg/m3, or an increase of 31.76% from the specific gravity of normal concrete.

An Automatic Recognition Approach for Tapping States Based on Object Detection

Monitoring tapping states, which reflects the smoothness of blast furnace (BF) production, is important in the blast furnace ironmaking process. Currently, these monitoring data are often recorded manually, which has limitations such as low reliability and high delays. In this study, we propose an automatic recognition approach for tapping states based on object detection, using furnace front monitoring videos combined with learning-based image processing technology. This approach addresses crucial aspects such as automatically recognizing the start and end times of iron tapping and slag discharging, accurately calculating their duration, and logging tapping sequences for multi-taphole operations. The experimental results demonstrate that this approach can meet the requirements of accurate and real-time recognition of tapping states and calculation of key monitoring data in industrial applications. The automatic recognition system developed based on this approach has been successfully applied in engineering projects, which provides real-time guidance for comprehensive monitoring, intelligent analysis, and operational optimization in blast furnace production.

Effect of Fluoride Ions in Slag on the Dynamic Change of the Interfacial Tension between Liquid Iron and Molten Slag

Effect of Fluoride Ions in Slag on the Dynamic Change of the Interfacial Tension between Liquid Iron and Molten Slag

Vocabulary related to iron manufacture and iron-working in Saami languages

In this article, etymologies of the lexical set related to iron manufacture and iron-working in the Saami languages are examined. The aim is to examine, from a linguistic perspective, when Saami speakers started to manufacture and work iron and from which direction they learned these activities. The data consists of 32 words relating to iron. Only the most central terms of the lexical set have been included, namely terms for ‘iron’; ‘steel’; ‘ore’; ‘iron slag’; ‘forge (v.)’; ‘forge (n.), smithy’; ‘furnace’; ‘smith’; ‘coal; ember’; ‘bellows’; ‘pliers’; ‘hammer’; ‘anvil’. The data was collected from dictionaries of the Saami languages. According to the data analysis, it seems that Saami speakers received their iron-related vocabulary mainly from two directions: Proto-Scandinavian and Finnic/Finnish. The southwestern Saami languages which are today spoken in central Scandinavia and Lule Saami received the vocabulary mainly from Proto-Scandinavian. The more northern and northeastern languages have borrowed words from Finnic/Finnish.

Durability Analysis of Concrete with the Substitution of Natural Aggregates by Copper and Pig Iron Waste

Background: The global scenario demands immediate actions to mitigate the environmental imbalances threatening the planet, reflected in natural disasters such as storms, floods, and severe droughts. This study evaluates the durability of concrete in the face of these challenges through carbonation, chloride penetration, and alkali-aggregate reaction tests, exploring the feasibility of producing sustainable concretes using copper ore waste and pig iron slag, available in the southern and southeastern regions of Pará due to the local mining activity. Materials and Methods: The methodology of the study involved the collection of copper waste and blast furnace slag, which were characterized through granulometric analysis, X-ray Diffraction (XRD), and X-ray Fluorescence (XRF). These materials were used as partial substitutes for fine and coarse aggregates in the production of concretes with different dosages. Durability tests were conducted, including accelerated carbonation, chloride penetration, and alkali-aggregate reaction. The analysis of the results aimed to assess the feasibility of these wastes as sustainable alternatives for civil construction. Results: The statistical results showed significance in the substitution of waste materials, highlighting copper waste and blast furnace slag as promising alternatives. The accelerated carbonation tests revealed that concretes with 75% and 100% waste exhibited lower susceptibility to CO₂ due to reduced porosity. In the chloride penetration test, concretes with 25% and 75% waste demonstrated lower NaCl penetration, indicating superior resistance. Furthermore, in the alkali-aggregate reaction test, the waste samples showed no reactive potential, as per NBR 15577-4, confirming their suitability for concrete production. Conclusion: A comparative analysis of the properties of these concretes in relation to conventional concrete revealed significant potential for replacing natural aggregates with waste materials that would otherwise be discarded, contributing to the reduction of environmental impact.

Utilizing steel slag to prolong the durability of reinforced concrete: corrosion resistance mechanisms

Utilizing steel slag to prolong the durability of reinforced concrete: corrosion resistance mechanisms

Potential Reuse of Ladle Furnace Slag as Cementitious Material: A Literature Review of Generation, Characterization, and Processing Methods

Ladle furnace slag (LFS), a by-product of steel refining, shows a promising reuse pathway as an alternative additive or substitute for Portland cement due to its high alkalinity and similar chemical composition to clinkers. However, LFS is often stored in large, open surface areas, leading to many environmental issues. To tackle waste management challenges, LFS can be recycled as supplementary cementitious material (SCM) in many cementitious composites. However, LFS contains some mineral phases that hinder its reactivity (dicalcium silicate (γ-C2S)) and pose long-term durability issues in the cured cemented final product (free lime (f-CaO) and free magnesia (f-MgO)). Therefore, LFS needs to be adequately treated to enhance its reactivity and ensure long-term durability in the structures of the cementitious materials. This literature review assesses possible LFS treatments to enhance its suitability for valorization. Traditional reviews are often multidisciplinary and explore all types of iron and steel slags, sometimes including the recycling of LFS in the steel industry. As the reuse of industrial by-products requires a knowledge of their characteristics, this paper focuses first on LFS characterization, then on the obstacles to its use, and finally compiles an exhaustive inventory of previously investigated treatments. The main parameters for treatment evaluation are the mineralogical composition of treated LFS and the unconfined compressive strength (UCS) of the final geo-composite in the short and long term. This review indicates that the treatment of LFS using rapid air/water quenching at the end-of-refining process is most appropriate, allowing a nearly amorphous slag to be obtained, which is therefore suitable for use as a SCM. Moreover, the open-air watering treatment leads to an optimal content of treated LFS. Recycling LFS in this manner can reduce OPC consumption, solve the problem of limited availability of blast furnace slag (GGBFS) by partially replacing this material, conserve natural resources, and reduce the carbon footprint of cementitious material operations.

Effect of freezing–thawing cycles and high temperatures on concretes containing partial replacement of fine grain blast and Electric Arc Furnace slags

This study examines the effects of local industrial by-products, such as iron slag and steel slag, as partial replacements of fine grain at 10%, 15%, and 25%, individually and combined. The research evaluates the impact on mechanical resistance under freeze–thaw cycles and high temperatures. Additionally, the study explores the effects of incorporating 0.3% polypropylene fibers by volume and 10% microsilica by cement weight (500 kg/m3). The durability of concrete samples exposed to freezing–thawing at the age of 28 days with 100 cycles and at temperatures of 400 °C and 800 °C at the age of 90 days in the gas furnace were investigated in terms of compressive strength. Samples subjected to 100 freeze–thaw cycles showed increased porosity and expansion of microcracks, leading to a loosened macrostructure and a 0.8% decrease in weight. Findings indicate that the partial replacement of slag in the fine grain and combining these materials with polypropylene and microsilica fibers improved mechanical properties like compressive strength. Additionally, the freeze–thaw cycle caused a 32.46% decrease in sample resistance compared to the control state. Moreover, incorporating 10% slag enhanced the mechanical properties of samples at 400 °C and 800 °C, with a lower resistance loss when compared to designs without additives. The inclusion of 10% microsilica and 0.3% polypropylene fibers, however, reduced sample resistance at 800 °C compared to 400 °C. Microstructural analysis of GGBS in concrete using Scanning Electron Microscopy (SEM) revealed that the addition of GGBS produces a denser matrix populated with more angular particles, resulting in improved bonding properties compared to plain concrete.

Upcycling Iron Oxide Scale Slag into a High‐Performance, Sustainable Ozone Catalyst

AbstractUpcycling iron slag into a monolithic catalyst has led to low‐cost heterogeneous catalytic ozonation (HCO) strategies for water treatment. The primary industrial challenges are the low chemical oxygen demand (COD) reduction rate in treating authentic wastewater and difficulties sustaining close‐loop reaction cycles. In this study, we present a monolithic catalyst transformed from low‐cost iron oxide scale slag (IOSM) for highly efficient, sustainable ozone catalysis. The IOSM, constituted of 59.70 % Fe2O3 and 40.30 % Fe3O4, effectively decomposes ozone into superoxide radicals (⋅O2−) through a close‐loop cyclic reaction facilitated by interfacial charge transfer. This mechanism enables super‐fast degradation of 100 mg L−1 tetracycline at ozone concentrations below 1.00 mg L−1 in just four minutes, with the iron leaching merely at 59 μg L−1 after 10 cycles. In tests with authentic antibiotic wastewater, the IOSM‐based HCO system achieves a record‐breaking 81.70 % COD reduction within two hours. This research underscores the potential of upcycling industrial waste into highly effective ozone catalysts for sustainable practices in wastewater treatment.

Upcycling Iron Oxide Scale Slag into a High-Performance, Sustainable Ozone Catalyst.

Upcycling iron slag into a monolithic catalyst has led to low-cost heterogeneous catalytic ozonation (HCO) strategies for water treatment. The primary industrial challenges are the low chemical oxygen demand (COD) reduction rate in treating authentic wastewater and difficulties sustaining close-loop reaction cycles. In this study, we present a monolithic catalyst transformed from low-cost iron oxide scale slag (IOSM) for highly efficient, sustainable ozone catalysis. The IOSM, constituted of 59.70 % Fe2O3 and 40.30 % Fe3O4, effectively decomposes ozone into superoxide radicals (⋅O2 -) through a close-loop cyclic reaction facilitated by interfacial charge transfer. This mechanism enables super-fast degradation of 100 mg L-1 tetracycline at ozone concentrations below 1.00 mg L-1 in just four minutes, with the iron leaching merely at 59 μg L-1 after 10 cycles. In tests with authentic antibiotic wastewater, the IOSM-based HCO system achieves a record-breaking 81.70 % COD reduction within two hours. This research underscores the potential of upcycling industrial waste into highly effective ozone catalysts for sustainable practices in wastewater treatment.

Organic and Inorganic Modifications to Increase the Efficiency in Immobilization of Heavy Metal (Zn) in Cementitious Composites-The Impact of Cement Matrix Pore Network Characteristics.

This research investigated the properties of modified cementitious composites including water purification from heavy metal-zinc. A new method for characterizing the immobilization properties of tested modifiers was established. Several additions had their properties investigated: biochar (BC), active carbon (AC), nanoparticulate silica (NS), copper slag (CS), iron slag (EAFIS), crushed hazelnut shells (CHS), and lightweight sintered fly ash aggregate (LSFAA). The impact of modifiers on the mechanical and rheological properties of cementitious composites was also studied. It was found that considered additions had a significantly different influence over the investigated properties. The addition of crushed hazelnut shells, although determined as an effective immobilization modifier, significantly deteriorated the mechanical performance of the composite as well as its rheological properties. Modification by iron slag allowed for a significant increase in immobilization properties (five-fold compared to the reference series) without a substantial impact on other properties. The negative effect on immobilization efficiency was observed for nanoparticulate silica modification due to its sealing effect on the pore network of the cement matrix. The capillary pore content in the cement matrix was identified as a parameter significantly influencing the immobilization potential of most considered modifications, except biochar and active carbon.

Hydrogen affection on softening and melting behaviours of high alumina sinter in gas-injection blast furnace

As the Al2O3 content increasing in iron ore, some problems presented in blast furnace (BF) processing, such as worsened burden permeability and slag viscosity. Injection of H2 may improve the permeability and reduce the CO2 emission of BF, because of its less density and higher reduction potential when temperature is higher than 820 °C. Therefore, the influence of H2 concentration on the softening and melting behaviour of high alumina sinter is a worth investigate topic. In this article, the high alumina sintering samples with Al2O3 content of 2.11 wt% are investigated in a specially designed experimental apparatus capable of continuously changing pressure on the burden. The results show that the softening temperature range of the samples is expanded and their melting temperature range is reduced with the increasing of H2 concentration from 0 vol% to 20 vol% in reduction gas. But the overall change on softening-melting temperature range is just from 280 °C to 310 °C, which is relatively small comparing with other references reported results. The addition of H2 promotes the reduction of FeO and is conducive to separate between the iron phase and slag phase before the charge droplet formation, which facilitates the aggregation and precipitation of metallic iron in soften state. Simultaneously, higher H2 concentration leads to more pronounced improvements in the permeability of the high alumina burden.

Viscosity of titanium slag in separating electric melting of a metallized mixture of perovskite and ilmenite concentrates

To assess the possibility of joint processing of ilmenite (FeTiO3) and perovskite (CaTiO3) concentrates using a duplex process involving solid-phase reduction of iron (metallization) and subsequent separating melting into pig iron and titanium slag, the properties of slag melts were studied. The crystallization beginning point (liquidus temperature) and the corresponding viscosity of titanium slag depend on its chemical composition. The increase in titanium oxides content results in increase of these properties, while the presence of iron and calcium oxides leads to their decrease. During the joint processing of ilmenite (IC) and perovskite (PC) concentrates, the CaO content in the slag can be adjusted by changing their PC/IC ratio, and the FeO fraction is determined by the degree of iron metallization during the preliminary reduction roasting of a concentrate mixture with a carbon reducing agent. To select the optimal PC/IC ratio the temperature dependences of the viscosity of model oxide melts of the TiO2–FeO–CaO–Al2O3–MgO system, similar in composition to the slags formed as a result of melting mixtures of perovskite and ilmenite concentrates within the range of PC/IC ratios equaling to 0.6÷1.4, and the metallization degree from 75 to 95% were determined. According to the results obtained, within the entire range of studied compositions and temperatures, the viscosity of slag melts does not exceed 0.8 Pa·s. That is to say, such slags will be sufficiently fluid at the tapping point if the melt temperature is higher than liquidus temperature — the crystallization beginning point. Increasing the PC/IC ratios when decreasing the metallization from 95 to 75%, results in a monotonous decrease in liquidus temperature and its corresponding viscosity from 1490 оC and 0.79 Pa·s up to 1270 оC and 0.17 Pa·s, respectively. It is recommended to use a charge containing equal mass fractions of concentrates (PC/IC equal to 1) at the consumption of carbon reducing agent based on metallization of 85% iron. In this case, slags with a relatively low iron oxide content (3.1%) will be fluid (0.38 Pa·s), and have liquidus temperature of 1400 оC which will allow carrying out top and bottom melt at operating temperatures of 1500–1550 оC.

Heavy metal contamination assessment and source attribution in the Vicinity of an iron slag pile in Hechi, China: Integrating multi-medium analysis

Heavy metal contamination assessment and source attribution in the Vicinity of an iron slag pile in Hechi, China: Integrating multi-medium analysis

Slag Inclusions in Iron Artifacts from Cemeteries at Kichigino I and Krasnaya Gorka, and the Metallurgy of the Early Iron Age Itkul Culture

Slag Inclusions in Iron Artifacts from Cemeteries at Kichigino I and Krasnaya Gorka, and the Metallurgy of the Early Iron Age Itkul Culture

Microstructural and wear properties of iron slag reinforced aluminum alloy (LM30) based composite prepared through a stir casting method

Aluminum alloys are widely used in various industries due to their as low density, high strength-to-weight ratio, and good corrosion resistance. However, their wear resistance is often inadequate for certain applications. Utilization of industrial waste materials, such as iron slag, as reinforcement in aluminum alloy matrix composites offers a sustainable approach to material development and waste management. The utilization of industrial waste materials for aluminum alloy matrix composite fabrication offers a waste utilization to material development. The loading of this reinforcement varied from 0 to 15 wt.% and different particle size range (220-140, 140-70, and 70-0 µm). A microscopic analysis indicated that the iron slag particles are spread uniformly inside the metallic matrix. There is also a reduction in the size of primary silicon, as well as morphological changes (acicular to globular shape). The wear behavior was calculated using a pin-on-disk wear set up in accordance with ASTM G99 standard. The composites were employed to dry sliding wear test under various operating conditions such as applied pressure (0.2–1.4 MPa), and sliding distance (0–3000 m). The 15F composite outperformed all other composite samples in terms of wear rate under all working conditions. When compared to the base alloy, it demonstrated a remarkable 67% drop in steady state wear rate. The enhancements in wear performance for the 15F composite were attributed to the effects of Fe slag reinforcement. The inclusion of iron slag particles induced strong interfacial bonding between matrix and reinforcement particles improving the durability of the mechanical mixed layer developed during relative motion. Importantly, the wear rate parameters of the 15F composite were similar to those of the brake drum material used in commercial applications. This emphasizes the composite suitability for usage in a variety of automobile components.