Search Results (45)

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 investigates the feasibility of producing an Fe-Cr-Mn complex alloy through the recycling of technogenic wastes from metallurgical operations. The feed materials comprised chromium-bearing dust collected from the gas-cleaning system of high-carbon ferrochrome production, iron–manganese ore fines (<10 mm) from the Tur deposit (Kazakhstan), and coal sludge used as a carbonaceous reducing agent. Thermodynamic modeling of the carbothermic reduction of Cr and Mn oxides and the predicted distribution of components among the metal, slag, and gas phases were performed using the HSC Chemistry 10 software package over a high-temperature range. At 1800 °C, the calculated chemical composition of the target alloy was as follows (wt.%): Cr-35.84, Mn-24.47, Si-16.25, Fe-22.63, and C-0.82. To validate the modeling results, experimental smelting trials were carried out in a 100 kVA electric arc furnace, producing both metallic and slag phases. The average composition of the metal phase was (wt.%): Cr-37.17, Mn-14.46, Si-11.48, Fe-33.23, C-3.48, P-0.15, and S-0.021. The experimental results indicate the formation of a Cr-Mn alloy with elevated Cr and Fe contents and a noticeable C level, confirming the carbothermic nature of the reduction reactions. The composition and microstructural features of the smelting products were examined by scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS). The findings demonstrate that the combined use of technogenic raw materials and a carbonaceous reductant enables the production of a Cr- and Mn-enriched metallic phase under satisfactory slag-forming conditions. Overall, the results confirm the potential of a resource-saving approach for valorizing fine technogenic wastes in the production of complex ferroalloys and for improving the recovery of target elements through optimization of the charge composition and smelting parameters. Full article

The metallurgical industry generates substantial amounts of heavy metal-containing solid waste, posing significant environmental and health risks. This study systematically evaluates the environmental behavior and ecological risks of heavy metals in four typical metallurgical wastes: jarosite slag (SW1), electric arc furnace ash (SW2), chromium-containing sludge (SW3), and acid-base sludge (SW4). We demonstrate that particle size fundamentally governs heavy metal mobility, with fine-structured SW1 and SW2 (D₅₀ = 4.76 µm and 1.34 µm) exhibiting enhanced metal mobility and bioavailability. In contrast, coarser SW3 and SW4 particles (D₅₀ = 268.83 µm and 133.94 µm) retain heavy metals in more stable forms. Among all metals analyzed, cadmium (Cd) presents the most severe ecological threat, with acid-extractable fractions reaching 52% in SW2 and 45% in SW3—indicating high release potential under changing pH conditions. Risk assessment confirms high to very high ecological risks for Cd in both SW2 and SW3. Moreover, under acidic leaching conditions, SW1 and SW2 show significantly higher cumulative toxicity than SW3 and SW4. These findings highlight the critical role of waste-specific properties in controlling heavy metal fate and provide a scientific basis for targeted risk management and sustainable remediation strategies. Full article

The article presents the results of a study on the production of a complex chromium–manganese–silicon-containing ferroalloy in a large-scale laboratory ore-thermal furnace using man-made waste—chromium-containing aspiration dust obtained during smelting of high-carbon ferrochrome, fines (−5 mm) of iron–manganese ore currently stored in landfills, and finely dispersed coal sludge formed during enrichment. A single-stage technology for the production of a new complex chromium–manganese–silicon-containing ferroalloy by carbothermal reduction is proposed. A metallurgical assessment of the initial charge materials was carried out by the X-ray diffraction (XRD) phase analysis, and metal samples of the obtained ferroalloy were studied by scanning electron microscopy (SEM) in combination with energy dispersive spectroscopy (EDS). The resulting ferroalloy has a complex microstructure with a predominance of carbide and intermetallic phases. A high degree of extraction of chromium (up to 80%), manganese (up to 75%), and silicon (up to 35%) was recorded. The average chemical composition of the obtained ferroalloy, wt.%: Cr—37.41; Mn—17.31; Si—11.84; C—3.81; P—0.14; S—0.02. The slag formed during the smelting of the ferroalloy has satisfactory technological properties: it is characterized by good fluidity, and it actively exits the furnace by gravity. Entanglement of metal kings in the slag is not observed. The results obtained confirm the technological feasibility of the utilization of technogenic raw materials for the production of complex ferroalloys of the FeCrMnSi type. Full article

The processing of fine and technogenic chromite-bearing raw materials accumulated in tailings and sludge storage facilities is a key challenge for sustainable metallurgical development. This paper presents the results of laboratory and pilot-scale studies on the application of vibro-briquetting technology for flotation concentrates and waste materials from JSC “TNC Kazchrome” (ERG). For the first time in Kazakhstan, a pilot-scale validation of vibro-briquetting of flotation chromite concentrates was carried out, resulting in pilot confirmation of the vibro-briquetting technology. The optimal technological parameters of the process were established, and the effectiveness of various types of binders was evaluated. Pilot-scale trials demonstrated that the use of organic and mineral binders ensures the production of durable briquettes with a low yield of fines (around 2%). Comparison with conventional agglomeration technologies (pelletizing, sintering, roller-press briquetting, extrusion briquettes) highlighted the advantages of vibro-briquettes in terms of energy efficiency, environmental performance, and suitability for fine raw materials. It was shown that composite binders (lignosulfonate + cement) provide enhanced strength and water resistance in briquettes, as well as optimal conditions for strength development during thermal–moisture treatment. The findings confirm the high potential of vibro-briquetting technology in Kazakhstan as an energy-efficient and environmentally friendly solution for the integrated utilization of local chromite resources. The proposed vibro-briquetting technology makes it possible to process previously unused gravity and flotation tailings of chromite ores from the Kempirsai Massif, thereby improving the comprehensive utilization of mineral resources and reducing environmental impact. This development is of great importance for Kazakhstan’s industry, as it represents the first pilot-scale testing of cold vibro-briquetting technology for flotation concentrates. Full article

Red mud, a by-product of aluminum production, leads to significant environmental challenges due to its alkalinity and presence of soluble compounds. This study explores its valorization through agglomeration with blast furnace sludge as a reducing agent to form self-reducing briquettes. Five C/Fe₂O₃ ratios (0.131, 0.262, 0.523, 0.840 and 1.000) were tested to determine the most effective reducing condition, with 0.840 emerging as optimal based on thermal analysis (mass loss of 27.44 wt.% at 1200 °C and iron formation specific energy of 450 J g⁻¹). Briquettes prepared with three agglomeration methods varying in water content (water/starch ratios of 6:1, 12:1 and 18:1) were evaluated through drop, compression and abrasion tests. The agglomeration method with a 12:1 water/solid ratio, involving both starch gelatinization and red mud water absorption, produced the most mechanically resistant briquettes (19.210 MPa). The mechanical and metallurgical properties of the 0.840-2W briquettes after reduction at 700, 950, 1200 and 1450 °C (temperature maintenance for 15 min) were assessed to define the best compromise between the reduction degree and mechanical strength. While reduction at 950 °C led to the weakest structure (0.449 MPa) but poor metallization, 1450 °C ensured the highest degree of reduction (94%) with adequate brittleness to facilitate a possible subsequent magnetic separation. Full article

A comprehensive study was conducted to investigate the influence of mineral waste on the thermal stability of foamed geopolymer materials. The study’s objects were steelmaking slag (SS) from the Taganrog Metallurgical Plant, drilling sludge (DS) from the Sutorminskoye oil field, and an ash and slag mixture (ASM) from the Novocherkasskaya SDPP. The utilisation of drilling sludge as an additive in the production of geopolymers has been proposed for the first time. The study involved the development of alkaline activators based on solutions of sodium and potassium silicates and their hydroxides. The samples were synthesised with varying proportions of steelmaking slag and drilling sludge, and physicochemical, mechanical and high-temperature studies were conducted to ascertain the optimal composition. X-ray phase analysis of the synthesised samples was conducted. An investigation was conducted into alterations in the phase composition of the material as a consequence of heat treatment. Proposals were hereby made for the mechanisms of the formation of new phases. The study identified an alkaline activator based on a solution of silicate and sodium hydroxide, with the introduction of 10% steelmaking slag into the component mixture, as the most effective mixture. The resultant geopolymers exhibited a density of 311 kg/m³ and an ultimate compressive strength of 1.54 MPa. Full article

In the process of producing ferroalloys, a large amount of secondary raw materials is formed, including slag, aspiration dusts and sludge. The recycling of secondary raw materials can create resources and bring environmental and economic benefits. Wet secondary raw materials (WSRMs) are characterized by a high chromium oxide content (averaging 24%), but due to their high moisture levels, they cannot be directly used in arc furnaces. As a strategic approach, mixing WSRMs with drier, more chromium-rich dusts (up to 45% Cr₂O₃) has been proposed. This not only reduces the overall moisture content of the mixture but also enhances the metallurgical value of the charge material. This paper presents the results of laboratory studies on the agglomeration of secondary wet raw materials using briquetting, extrusion and pelletizing methods. The main factors influencing the quality of the resulting product were analyzed, including the method of agglomeration, the composition of the mixture, as well as the type and dosage of the binder component. The strength characteristics of the finished agglomerated samples were evaluated in terms of resistance to splitting, impact loads and falling. Notably, the selected binders are organic and polymer substances capable of complete combustion under metallurgical smelting conditions. Full article

The environmental impacts of industrial processes have increased the demand for sustainable alternatives in wastewater treatment. Conventional chemical coagulants, though widely used, can generate toxic residues and pose environmental and health risks. Biocoagulants, derived from natural and renewable sources, offer a biodegradable and eco-friendly alternative. This review explores their potential to replace synthetic coagulants by analyzing their origins, mechanisms of action, and applications. A total of 15 studies published between 2020 and 2025 were analyzed, all focused on industrial wastewater. These studies demonstrated that biocoagulants can achieve similar, or the superior, removal of turbidity (>67%), solids (>83%), and heavy metals in effluents from food, textile, metallurgical, and paper industries. While raw materials are often inexpensive, processing costs may increase production expenses. However, life cycle assessments suggest long-term advantages due to reduced sludge and environmental impact. A textile industry case study showed a 25% sludge reduction and improved biodegradability using a plant-based biocoagulant compared to aluminum sulfate. Transforming this waste into inputs for wastewater treatment not only reduces negative impacts from disposal but also promotes integrated environmental management aligned with circular economy and cleaner production principles. The review concludes that biocoagulants constitute a viable and sustainable alternative for industrial wastewater treatment. Full article

The historical industrial waste deposit Gater was used to dispose of different metallurgy wastes from lead and zinc production. The metallurgical waste deposit was situated in the open space, between the tailing waste deposit Žitkovac and river Ibar flow. Large amounts of lead-containing wastes are produced in the non-ferrous metallurgical industry, such as lead ash and lead slag generated in Pb smelting, lead anode slime, and lead sludge produced in the raw lead refining process. In addition to the lead concentration, numerous valuable components are found in the lead refinery waste from the group of Critical Raw Materials, such as antimony, arsenic, bismuth, copper, nickel, magnesium, scandium, as well as Rare-Earth Elements. Samples with eight characteristic points were taken to obtain relevant data indicating a possible recycling method. The chemical composition analysis was conducted using ICP; the scanning was completed using SEM-EDS. The mineralogical composition was determined by using XRD. The chemical analysis showed a wide range of valuable metal concentrations, from Ag (in the range from 14.2 to 214.6, with an average 86.25 mg/kg) to heavy metals such as Cu (in the range from 282.7 to 28,298, with an average 10,683.7 mg/kg or 1.0683% that corresponds to some active mines), Ni and Zn (in the range from 1.259 to 69,853.4, with an average 14,304.81 mg/kg), Sc (in the range from 2.4 to 75.3, with an average 33.61 mg/kg), Pb (in the range from 862.6 to 154,027.5, with an average 45,046 mg/kg), Sb (in the range from 51.7 to 18,514.7, with an average 2267.8 mg/kg), Ca (in the range from 167.5 to 63,963, with an average 19,880 mg/kg), Mg (in the range from 668.3 to 76,824.5, with an average 31,670 mg/kg), and As (in the range from 62.9 to 24,328.1, with an average 5829.53 mg/kg). The mineralogy analysis shows that all metals are in the form of oxides, but in the case of As and Fe, SEM-EDS shows some portion of elemental lead, pyrite, and silica-magnesium-calcium oxides as slag and tailing waste residues. The proposed recovery process should start with leaching, and further investigation should decide on the type of leaching procedure and agents, considering the waste’s heterogeneous nature and acidity and toxicity. Full article

The recycling of waste materials that are usually expensive to dispose of, such as carbon fiber reinforced plastic (CFRP) dust and ferrous dust or sludge, can open up interesting economic prospects and free up landfill space. The agglomeration process is used to combine these two types of waste and produce an aggregate that can be used in shaft furnaces. The carbon contained in the CFRP dust serves as a potential reducing agent in metallurgical processes. The report shows the technical parameters of the wet agglomeration with subsequent sintering for the production of the pellets and provides evidence of the material recycling of the carbon fiber waste. A comparison with primary pellets shows the suitability. Full article

This research investigates the sorption efficiencies of various adsorbents—synthesized Hydrotalcite, natural zeolite Clinoptilolite, synthetic zeolite, and waste sludge from aluminum anodic oxidation—for simultaneous removal of Cl⁻ and Ca²⁺ ions from synthetic CaCl₂ solutions and wastewater from EAFD recycling. This study addresses the challenges of wastewater purification options, which were not previously addressed in other studies. The high alkalinity and ionic pollutants in EAFD wastewater make the purification process complex. The fact that adsorbents tested in this study were prepared from metallurgical waste predetermines the process to be more sustainable. Adsorbents were thoroughly characterized before and after calcination and sorption using techniques like AAS, LIBS, XRD, BET, BJH, SEM-EDS, and FTIR spectroscopy. Synthetic zeolite achieved near-complete removal of Ca²⁺ ions, while calcined Hydrotalcite at 500 °C excelled in the simultaneous removal of Cl⁻ and Ca²⁺. Equilibrium sorption capacities of HT were 50.3 mg/g for Cl⁻ and 37 mg/g for Ca²⁺ after 360 min, with efficiencies reaching 85% for Ca²⁺ and 83% for Cl⁻. Additionally, HT effectively removed 82% Pb, 91% Cr, and 40% SO₄²⁻ in 24 h of the sorption process. These findings highlight HT as a promising solution for industrial wastewater treatment, offering sustainable and efficient pollutant removal. Full article

The modern metallurgical industry produces approximately 90% of the volume of all produced steel; for this, integrated technology based on fossil materials such as coal, fluxes, and especially iron ore is used. This industry generates large amounts of waste and by-products at almost all stages of production. Alternative iron and steel production technologies based on iron ore, methane, or pure hydrogen are also not waste-free. To ensure sustainable waste management, efforts are made to seal processes as well as capture and recycle dusty waste. This work presents the results of research on the processing of sludge resulting from the dedusting of the basic oxygen furnace (BOF) process and landfilling in a lagoon. The work discusses the treatment of fine dusty sludge hydrated to 26–60% H₂O, to which various amounts of caking agents were added; also discussed are the rheological characteristics of the tested suspension systems, the possibility of forming these systems into larger fractions, and rapid drying using 100–600 W microwaves with a drying time of 1–9 min. The aim was to identify, describe, and characterize the parameters of the agglomeration process and obtain a product that was durable enough to transport and dose into slag baths in order to reduce iron oxides in liquid phases. During the research, completely dried briquettes with an appropriate strength were obtained. The study demonstrates that microwave drying at 300 W for 6 min achieved complete drying with a weight loss of 35%, whereas a higher-power treatment at 750 W for 2 min enhanced compressive strength by up to 95% and reached 15 N/psc, which was comparable with green iron ore pellets. This approach offers a sustainable alternative to traditional methods, but with a reduced drying time. Full article

The study is the first to examine the combined use of blast-furnace sludge as a source of microelements and converter slag as a soil-deoxidizing agent in oat (Avena sativa L.) cultivation in sod-podzolic soils. It has been established that blast-furnace sludge is a highly dispersed waste, which contains about 50% iron, 7% zinc, and a small amount of calcium, silicon, magnesium, aluminum, and sulfur. Hazardous components such as lead, arsenic, etc., are not detected. Converter slag comprises porous granules up to 3 mm in size, consisting mainly of calcium compounds (CaO, Ca(CO)₃, CaSiO₃, CaFe₂O₄) and a small amount of Mn, Al, and Mg trace elements. In a laboratory experiment, blast-furnace sludge increased the germination of oats by 5–10%, regardless of the addition of a deoxidizer (slag), but at the same time suppressed the growth of stem length by a maximum of 18% at 1 g∙kg⁻¹. The addition of slag raised substrate pH and increased the index by 8% at a sludge concentration of 0.1 g∙kg⁻¹. Root length in deoxidizer-free variants increased by 50–60% and with the addition of slag by 27–47%. Root dry mass also increased under the addition of sludge by 85–98%; however, the addition of slag reduced the indicator to the control level. In a field experiment with the combined application of waste, an increase in yield by more than 30% was shown. When soil was treated with slag and sludge, the height of plants increased by an average of 18%. It should be noted that the introduction of waste did not affect the quality of the grain. The use of slag increased the lead content in the soil, which is probably due to the sorption properties of calcium compounds in the slag, since lead was not found in the analyzed waste. Presumably, lead is sorbed by slag from the lower soil horizons, concentrating and immobilizing it in the upper layer. This version is supported by the absence of lead accumulation in straw and oat grain. The zinc-containing sludge increased the content of this element by 33% in the soil, as well as by 6% in straw and by 14% in grain. Thus, we found that the studied metallurgical wastes can be used as nutrients for agriculture, both individually and jointly. Overall, the proposed approach will contribute both to reducing the amount of accumulated waste and to improving the efficiency and sustainability of agricultural production and CO₂ sequestration. However, the features of the accumulation of heavy metals in soil and plants under the influence of the analyzed types of waste require more in-depth study, including within the framework of long-term field experiments. Full article

The paper presents an analysis of the effective use of a mixture of steel sludge (S1) and slag (S2) from the converter process of steel production for the production of cement mortars. Metallurgical waste used in the research, which is currently deposited in waste landfills and heaps near plants, posing a threat to groundwater (possibility of leaching metal ions present in the waste), was used as a substitute for natural sand in the range of 0–20% by weight of cement (each). The obtained test results and their numerical analysis made it possible to determine the conditions for replacing part of the sand in cement mortars with a mixture of sludge and slag from a basic oxygen furnace (BOF) and to determine the effects of such modification. For the numerical analysis, a full quadratic Response Surface Model (RSM) was utilized for two controlled factors. This model was subsequently optimized through backward stepwise regression, ensuring the inclusion of only statistically significant components and verifying the consistency of residual distribution with the normal distribution (tested via Ryan-Joiner’s test, p > 0.1). The designated material models are helpful in designing ecological cement mortars using difficult-to-recycle waste (i.e., sludge and converter slag), which is important for a circular economy. Mortars modified with a mixture of metallurgical waste (up to 20% each) are characterized by a slightly lower consistency, compressive and flexural strength, and water absorption. However, they show a lower decrease in mechanical strength after the freezing–thawing process (frost resistance) compared to control mortars. Mortars modified with metallurgical waste do not have a negative impact on the environment in terms of leaching heavy metal ions. The use of a mixture of sludge and steel slag in the amount of 40% (slag/sludge in a 20/20 ratio) allows you to save 200 kg of sand when producing 1 m³ of cement mortar (cost reduction by approx. EUR 5.1/Mg) and will also reduce the costs of the environmental fee for depositing waste. Full article