Iron Slag Research Articles

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.

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.

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

Silicate slag inclusions in iron artifacts from the Trans-Urals and in iron slags from sites of the Itkul culture were analyzed to assess the geochemical characteristics of iron ore sources exploited during the Early Iron Age. Slag inclusions were found in 19 out of 25 samples from Kichigino I and Krasnaya Gorka. For comparison, we used 12 iron slag samples from Early Iron Age and medieval sites near Lake Irtysh and from Zotino mine. Via statistical analysis, four geochemical groups were separated, each including one or more Kichigino artifacts, which suggests a variety of iron ore sources used by the nomads. Slags and artifacts of the first group are associated with infiltration-sedimentary ironstone ores of the Middle Trans-Urals. Smithing slag from the Itkul site of Shatanov V suggests that these ores were already smelted in the Early Iron Age. The fact that group 1 includes only one artifact from Kichigino I demonstrates that the nomads of the Southern Trans-Urals obtained iron mainly from other sources. Group 2 is characterized by a higher content of Mn and sometimes Ba and S in inclusions. This may attest to the use of Fe-Mn ironstone associated with barite-polymetallic deposits of Central Kazakhstan. Group 3 shows an elevated content of CaO and MgO, indicating the use of ironstone from platform carbonate strata. In the fourth group, the content of K2O is high, and that of MnO, low.

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

Heavy metals, such as mercury, cadmium, and nickel, may contaminate human inhabited environments, with critical consequences for human health. This study examines the health impacts of heavy metal pollution from an iron slag pile in Hechi, China, by analyzing heavy metal contamination in water, sediment, soil, and crops. Here, the Nemerow pollution index (NI) indicated severe pollution at most sampling sites, the mean NI of groundwater, and surface water had reached 594.13 and 26.79, respectively. Bioaccumulation of mercury (Hg), cadmium (Cd), and nickel (Ni) was noted in crops, cucumbers showed comparatively lower risk levels. Logarithmic surface water-sediment partition coefficient calculations indicated that heavy metals such as chromium (Cr), ferrum (Fe), zinc (Zn), copper (Cu), Ni, arsenic (As), and lead (Pb) tend to accumulate in sediments. There was a high risk in groundwater (67.48–6590.54) and surface water (13.73–2500.85). Variably influenced by rainfall, these metals can be diluted and mobilized from surface water and sediments, thereby changing the contamination levels and ecological risks. Probabilistic health risk assessments indicated that health risks were higher in children than in adults, the mean total carcinogenic risk values of soil, groundwater, and surface water, were 6.79E-04, 4.20E-06, and 1.15E-6 for children, respectively. Moderate soil pollution is the main health hazard. A Positive Matrix Factorization model attributed over 60% of the pollution to slag stacking. Biotechnologies, solidification/stabilization techniques, field management, and institutional controls, driven by principles of green, low-carbon, and economic efficiency may mitigate. These findings contribute to the management of heavy metal pollution in iron slag pile areas.

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.

Role of the Biogenic Carbon Physicochemical Properties in the Manufacturing and Industrial Transferability of Mill Scale-Based Self-Reducing Briquettes

The recovery of iron contained in mill scale rather than iron ore can be considered a promising valorization pathway for this waste, especially if carried out through reduction using biogenic carbon sources. Nevertheless, the physicochemical properties of the latter may hinder the industrial transferability of such a pathway. In this work, the mechanical and metallurgical behavior of self-reduced briquettes composed of mill scale and four biogenic carbons (with increasing ratios of fixed carbon to volatile matter and ash) was studied. Each sample achieved mechanical performance above the benchmarks established for their application in metallurgical furnaces, although the presence of alkali compounds in the ash negatively affected the water resistance of the briquettes. In terms of metallurgical performance, although agglomeration successfully exploited the reduction by volatiles from 750 °C, full iron recovery and slag separation required an amount of fixed carbon higher than 6.93% and a heat treatment temperature of 1400 °C. Finally, the presence of Ca-, Al-, and Si- compounds in the ash was essential for the creation of a slag compatible with steelmaking processes and capable of retaining both phosphorus and sulfur, hence protecting the recovered iron.

Destructive and non-destructive strength performance of iron slag recycled aggregate concrete using regression and grey correlation analysis

The future construction industry will demand for sustainable concrete, either by recycling or direct incorporation of industrial by-products for effective solution of ecological concerns. The paper covers, outcomes of an investigation conducted to assess the ‘performance of iron slag (0–30 %) recycled aggregate concrete (ISRA) with different levels of recycled (0–100 %) concrete aggregates (RCA)’ using destructive (DT) ‘(compressive, split-tensile and flexure strength)’ and non-destructive ‘(pulse velocity, electrical resistivity and rebound hammer)’ testing (NDT). The strength characters were evaluated to develop statistical regression and grey co-relations. ISRA concrete resulted majorly in decrease of pulse velocities, electrical resistance (up to 28 %) and rebound numbers (by 10) at higher alteration levels. The correlation coefficients were evaluated using linear regression and grey analysis. The grey correlations resulted in visible variations, indicating disparity in magnitude of ISRA concrete. The higher regression (>0.75) and grey coefficients (GRG>0.8) postulates higher probability of accuracy, successfully validate the outcomes.

Deadman Behavior and Slag–Iron–Coke Interaction of Low Carbon and Safety Blast Furnace: A Review

The elucidation of the deadman's behavior and the interaction between slag–iron–coke within the blast furnace hearth are essential for the realization of low‐carbon and safe production. In this review, the macrostate of the deadman, the interactions between slag–iron–coke, carburizing behaviors, and renewal mechanisms are comprehensively examined. First, the formation and state of the deadman, voidage, and the distribution of coke sizes within the blast furnace hearth are characterized. The average coke particle size ranges from 20 to 30 mm, and the deadman void fraction of 30–50%. Second, the interaction between slag–iron–coke as well as the occurrence state of the mineral layer at the interface within the deadman is elucidated. The ash composition and content of coke are the key factors affecting the slag–iron–coke interaction and interface phase composition. Third, the influence exerted by critical factors such as the physical properties of the carbon source, molten iron, and temperature on the carburizing behavior are analyzed, with the renewal mechanisms of the deadman also being disclosed. Finally, three future focal areas are proposed: characterization and intelligent monitoring of deadman permeability, analysis of slag–iron–coke properties and interface mineral layers control, and in‐depth analysis of deadman renewal and carbon carburization in molten iron. It is anticipated that the studies will enhance the comprehension of deadman behavior and the interactions between slag–iron–coke, thereby fostering the blast furnace's sustainable development.

Research on strip surface defect detection based on improved YOLOv5 algorithm

In the production process of hot rolled strip, there will inevitably be defects such as iron scale, slag inclusion and scratch on the surface, and there is no effective identification method for these defects. Therefore, based on the improved YOLOv5s algorithm, this article proposes an improved YOLOv5s-GCB model by introducing the coordinate attention module, improving the feature fusion structure and lightening the feature extraction backbone network. The experiment shows that the precision of YOLOv5s-GCB is 89.7%, recall is 90.2% and mAP@0.5 is 93.1%, which are 2.1%, 3.0% and 1.6% higher than YOLOv5s, respectively. The average detection time of a single image is 7.9 ms, and the detection speed is improved. Finally, the ablation experiment shows that the proposed improved strategy is feasible, and the detection effect of YOLOv5s-GCB is further verified by the comparison experiment with other target detection models. Therefore, it can be concluded that the proposed method provides an important reference for the detection of indicated defects in strip steel.

Enhancing textile wastewater sustainability through calcium hypochlorite oxidation and subsequent filtration with assistance from waste blast furnace iron slag

AbstractThe textile industry is vital to Bangladesh's economy, employing over three million women and being the top foreign exchange earner. However, it severely impacts the environment because of untreated wastewater discharge. High treatment costs, reliant on expensive imported chemicals, worsen the issue. The Environmental Conservation Rules (ECR) 2023 of Bangladesh requires textile wastewater discharge to have a colour of less than 150 Pt‐Co, which current systems struggle to meet affordably. A pilot project tested a sustainable solution using chemical oxidation with calcium hypochlorite and sand filtration with blast furnace iron slag. This method effectively removed colour, and the treated water showed total dissolved solids (TDS) levels of 157 ± 4 mg/L, total suspended solids (TSS) levels of 8 ± 2 mg/L and chemical oxygen demand (COD) levels of 9 ± 3 mg/L, with reductions of 92%, 87% and 94%, respectively, making it a viable solution for resource‐limited economies.

Comprehensive Utilization and Control Measures of Iron and Steel Slag

With the increase of steel production, the amount of steel slag piled up is on the rise. The article analyzes the current situation of blast furnace slag utilization, elaborates on the current treatment technology of blast furnace slag, and points out that in the future, the utilization of blast furnace slag will develop towards the direction of developing high value-added products, and the sensible heat recovery rate of blast furnace slag is expected to increase. Analyze the current application status and treatment process of converter slag. The comprehensive treatment technology of converter slag is limited by multiple factors, and it is proposed to control converter slag from the production source through "slag recycling".

Carbon dioxide removal efficiency of iron and steel slag in seawater via ocean alkalinity enhancement

Ocean alkalinity enhancement (OAE) via the enhanced weathering of alkaline minerals is a promising carbon dioxide removal (CDR) technology. Theoretically, these includes iron and steel slags, although their dissolution kinetics in seawater are unknown. Here, we conducted lab-scale experiments to assess the alkalinity generation potential and dissolution kinetics of various slags in seawater. We show that the alkalinity generated per mass of iron slag was logarithmic, i.e., higher amounts of iron slag added had diminishing alkalinity returns. In contrast, the relatively quick dissolution of steel slags and their linear generation of alkalinity per mass of feedstock dissolved in seawater makes them better OAE candidates. Furthermore, despite the presence of potentially toxic metals in these feedstocks, their low to non-existent presence as dissolution products suggests that harmful concentrations should not be reached, at least for the slag tested here. Finally, if all steel slag produced annually was used for OAE, between 10 and 22 gigatonnes of CO2 could be captured cumulatively by 2,100, highlighting significant CDR potential by slags.

Preparation and Performance Study of SiC-Reinforced Fe-Based Wear-Resistant Composite Grinding Media.

During industrial and laboratory processes involving material grinding, the grinding media endure prolonged high-collision and friction environments, resulting in substantial wear. Consequently, this study adopts the hot-pressing sintering technique in powder metallurgy to prepare SiC-reinforced Fe-based wear-resistant composite grinding media, aiming to increase wear performance. For this purpose, Fe with 10 wt% SiC powders were milled for the fabrication of the composite. Then, sintering was performed by hot press at 1100 °C in a furnace. Scanning electron microscopy (SEM) and X-ray diffraction were employed to investigate the microstructures and phase of SiC-reinforced Fe-based matrix composite. Subsequently, comparative performance evaluations of the newly developed grinding media and traditional chromium-based media were conducted in terms of wear rate and grinding efficiency. The wear resistance tests revealed that the SiC-reinforced composite media displayed significantly superior wear resistance across various abrasives compared to the chromium-containing alternatives. Specifically, the composite media achieved a wear rate reduction of 2.9 times against standard sand over 1 h, and 2.3 and 2.4 times against sandstone and iron slag, respectively. Moreover, extended grinding for 3 hours further enhanced these reductions to 3.1, 2.4, and 2.7 times, respectively. Additionally, efficiency assessments indicated that at a 1:1 material ratio, the composite media outperformed the chromium-containing media in grinding efficiency by 7.5%, 12.5%, and 10.3% for standard sand, sandstone, and iron slag, respectively. Further increasing the material ratio to 3:1 resulted in efficiency improvements of 7.4%, 17.5%, and 11.3%, correspondingly.

Recycling of iron and steel slag for carbon reduction and low‐environment load application

AbstractThe high‐value utilization of blast furnace slag (BFS) and steel slag (SS) as a valuable resource in the field of carbon reduction represents a green revolution, and also is an indispensable path toward breaking through resource and environmental constraints and achieving high‐quality, sustainable development through solid waste utilization in the steel industry. Achieving resource recycling while harnessing the untapped latent energy of resources and exploring their carbon sequestration capabilities has become a crucial avenue for further valorization through waste utilization. BFS and SS discharged from iron‐making or steel‐making furnaces carry a significant amount of latent heat, especially the calcium oxide component in SS, which gives it a unique advantage in the field of comprehensive BFS and SS utilization and carbonation‐based SS utilization. This article discusses the current research status of low‐carbon‐waste‐heat utilization in the production of microcrystalline glass, cementitious materials, functional adsorbents, and other products through front‐end modification of molten BFS and SS. This report also provides an overview of carbon capture by utilizing BFS and SS, offering insights into the research directions for subsequent heat recovery, online quality adjustment, high‐value utilization, and carbon sequestration using BFS and SS in the steel industry.

Environmental behaviour of iron and steel slags in coastal settings

Iron and steel slags have a long history of both disposal and beneficial use in the coastal zone. Despite the large volumes of slag deposited, comprehensive assessments of potential risks associated with metal(loid) leaching from iron and steel by-products are rare for coastal systems. This study provides a national-scale overview of the 14 known slag deposits in the coastal environment of Great Britain (those within 100 m of the mean high-water mark), comprising geochemical characterisation and leaching test data (using both low and high ionic strength waters) to assess potential leaching risks. The seaward facing length of slag deposits totalled at least 76 km, and are predominantly composed of blast furnace (iron-making) slags from the early to mid-20th Century. Some of these form tidal barriers and formal coastal defence structures, but larger deposits are associated with historical coastal disposal in many former areas of iron and steel production, notably the Cumbrian coast of England. Slag deposits are dominated by melilite phases (e.g. gehlenite), with evidence of secondary mineral formation (e.g. gypsum, calcite) indicative of weathering. Leaching tests typically show lower element (e.g. Ba, V, Cr, Fe) release under seawater leaching scenarios compared to deionised water, largely ascribable to the pH buffering provided by the former. Only Mn and Mo showed elevated leaching concentrations in seawater treatments, though at modest levels (<3 mg/L and 0.01 mg/L, respectively). No significant leaching of potentially ecotoxic elements such as Cr and V (mean leachate concentrations <0.006 mg/L for both) were apparent in seawater, which micro-X-Ray Absorption Near Edge Structure (μXANES) analysis show are both present in slags in low valence (and low toxicity) forms. Although there may be physical hazards posed by extensive erosion of deposits in high-energy coastlines, the data suggest seawater leaching of coastal iron and steel slags in the UK is likely to pose minimal environmental risk.

Influences of silicate fertilizers containing different rates of iron slag on CH4 emission and rice (Oryza sativa L.) growth

Influences of silicate fertilizers containing different rates of iron slag on CH4 emission and rice (Oryza sativa L.) growth

Analysis of the melting process of carbon-bearing pellets in iron bath, slag bath and graphite crucible

Background With the increase in the amount of scrap steel in society, the proportion of electric furnace steelmaking is increasing year by year, especially in China. Due to the high Zn content, the electric furnace arc dust (EAFD) needs to be recovered by non-blast furnace process. Due to EAFD containing a large amount of zinc ferrite, it needs to be recovered by fire process. It is a promising process to melt the EAFD pellets to get the discount and zinc-rich secondary ash. Methods To clarify the melting behavior of pellets in the metallurgical process, the slag phase diagram and the effect of temperature and FeO on slag viscosity were calculated using FactSage, and the melting process of electric furnace arc dust (EAFD) pellets in a graphite crucible, iron bath, and slag bath were experimentally investigated. Results The experimental results show that the viscosity of the slag system decreases with increasing temperature and FeO content, and the effect of FeO on viscosity is greater. The viscosity decreased from 0.305 to 0.276 Pa·s when the FeO content in the slag was increased from 0 wt. % to 2 wt.% at 1773 K. The melting process of the EAFD pellets in an iron bath and graphite crucible was consistent, and after the formation of liquid-phase slag in the pellets, the liquid-phase slag was diffused to melt the pellets. Conclusions The iron bath improved the heat transfer conditions of the pellets, reducing the smelting time from 600 to 360 s. The slag bath promoted the slagging reaction of the contact part to change the pellet melting process and increase the pellet melting speed, and the EAFD pellets melted within 240 s in a slag bath.