Search Results (33)

Copper slag, a by-product of copper ore and concentrate smelting, is rich in non-ferrous metals; therefore, it has been considered a valuable raw material in recent years. This study aimed to compare the extraction of zinc, copper, and cobalt from two types of copper slag from a dump located near the village of Eliseyna, Bulgaria, which differ in mineralogical composition and chemical content, using indirect bioleaching with a spent medium of Aspergillus niger and Penicillium ochrochloron. Chemical leaching with sulphuric acid revealed that zinc and cobalt existed mainly as an acidic-soluble phase in both types of copper slag. In contrast, it contained 50–75% of the total copper content. Each fungal species was cultivated for one week, and the biomass and the spent medium were separated a week later. Owing to the production of a higher concentration of citric acid, A. niger facilitated more efficient base metal recovery. However, their effective recovery from the acidic-soluble phase required leaching at a 5% pulp density and supplementing the spent medium with sulphuric acid. The temperature played a secondary role. Conclusions: Non-ferrous metal extraction from copper slag exposed to weathering using a spent medium supplemented with sulphuric acid was achieved under milder leaching conditions and with better selectivity. In contrast, slag unaffected by weathering behaved as a refractory due to the worsened results of base metal extraction under similar experimental conditions. Full article

Annual oyster production in southern Korea reaches about 300,000 tons, generating an equivalent amount of waste oyster shells. Most are illegally dumped or stockpiled along coastlines, causing serious environmental issues. This study utilized machine learning to predict the compressive strength of oyster shell cementitious composites. A total of 336 datasets were used, including 189 experimental results and 147 from published literature. Input variables were water-to-cement ratio (W/C), silica fume, blast furnace slag, superplasticizer content, and curing conditions. Algorithm selection compared the performance of Ridge Regression, Support Vector Regression, Artificial Neural Network, and Random Forest (RF), with RF exhibiting the highest predictive performance (R² = 0.8411). Ensemble algorithms including XGBoost, AdaBoost, Extra Trees, and LightGBM were optimized using GridSearchCV. Among these, LightGBM showed the best predictive capability with a mean absolute error of 3.1671, mean squared error of 17.8054, root mean square error of 4.2196, and R² of 0.9042. SHAP analysis revealed that W/C and superplasticizer were the most influential variables. Oyster shells showed a negative correlation with sand, indicating the role of oyster shells as a substitute material. Thus, cementitious composites can maintain compressive strength and serve as sustainable construction materials when waste oyster shells are incorporated with appropriate admixtures. Full article

A significant portion of coal mined in Kazakhstan is mainly used for fuel energy and metallurgy. Approximately 60% of electricity is generated by coal-fired power engineering. About 19 million tons of ash and slag waste (ASW) are annually sent to dumps. After coal combustion, in ASW not only are natural radioactive nuclides NRN (U²³⁸, Th²³², K⁴⁰) concentrated, but also rare and rare earth elements (REE). In this regard, ASW that essentially turns into quasi-technogenic deposits of NRN and REE, requires systemic measures for their utilization. The possibilities of extracting REE from coal power-industry waste are estimated based on the analysis of the concentration of REE (Ce, La, Nd, Sm, etc.), NRN (U²³⁸, Th²³² and their decay products, K⁴⁰) and the established significant correlations between rare earth and radioactive elements. The purpose of this paper is to study the natural radioactivity of coals and ash and slag waste as potential raw materials for assessing the quality and extracting rare earth metals. The stated purpose involves solving the following problems: studying the features of the NRN and REE distribution in coals and ash and slag waste; assessing the possibility of using ash and slag waste as a promising source of REE extraction based on nuclear radiometric studies; and studying the spectrometry of natural gamma radiation for assessing the quality of coals. Full article

In the process of the work of a coal power station is formed ash and slag, which, along with process water, are deposited in the dumps. Coal ash waste dumps significantly degrade the surrounding environment due to their unprotected surfaces, which are highly susceptible to wind and water erosion. This results in the dispersion of contaminants into adjacent ecosystems. Pollutants migrate into terrestrial and aquatic systems, compromising soil quality and water resources, and posing documented risks to the environment and human health. Primary succession on the coal ash dumps of the Apatity thermal power plant (Murmansk Region, NW Russia) was initiated by cyanobacterial colonization. We studied cyanobacterial communities inhabiting three spoil sites that varied in time since decommissioning. These sites are characterized by exceptionally high concentrations of calcium and magnesium oxides—levels approximately double those found in the region’s natural soils. A total of 18 cyanobacterial taxa were identified in disposal sites. Morphological analysis of visible surface crusts revealed 16 distinct species. Furthermore, 24 cyanobacterial strains representing 11 species were successfully isolated into unialgal culture and tested with a molecular genetic approach to confirm their identification from 16S rRNA. Three species were determined with molecular evidence. Cyanobacterial colonization of coal fly ash disposal sites begins immediately after deposition. Primary communities initially exhibit low species diversity (four taxa) and do not form a continuous ground cover in the early years. However, as succession progresses—illustrated by observations from a 30-year-old deposit—spontaneous surface revegetation occurs, accompanied by a marked increase in cyanobacterial diversity, reaching 12 species. Full article

As a legacy of historical metal mining and the processing and smelting of metalliferous ores, metal pollution is a serious environmental problem in many areas around the globe. This review summarizes the history, technical development and environmental hazards of historic metal mining and metallurgical activities in the Harz Region (Germany), one of the oldest and most productive mining landscapes in Central Europe. The release of large amounts of metal-containing waste into rivers during historic ore processing and the ongoing leaching of metals from slag heaps, tailings dumps and contaminated soils and sediments are the main sources of metal pollution in the Harz Mountains and its foreland. This pollution extends along river systems with tributaries from the Harz Mountains and can even be detected in mudflats of the North Sea. In addition to fluvial discharges, atmospheric pollution by smelter smoke has led to long-term damage to soils and vegetation in the Harz Region. Currently, the ecological hazards caused by the legacy pollution from historical metal mining and metallurgy in the Harz Region are only partially known, particularly regarding the effects of changes in river ecosystems as a consequence of climate change. This review discusses the complexity and dynamics of human–environment interactions in the Harz Mountains and its surroundings, with a focus on lead (Pb) pollution. The paper also identifies future research directions with respect to metal contamination. Full article

Millions of tons of slag and clinker can be found in the dumps of enterprises across the Republic of Kazakhstan. The goal of this project is to create a technology that conserves energy in waste treatment. The novelty of the work is the discovery of a new phenomenon, which shows that in the melt layer, there are two reactions opposite in direction and intensity: slow reactions of the decomposition of complex components into simple molecules and rapid responses of the formation of complex components from simple molecules. The dominance of one of the two reactions affects the process’s fuel consumption. Using this phenomenon, a melting reactor was created, which will reduce specific fuel consumption by 3–4 times compared to a Waelz kiln. It is shown that using a new method of CO₂ decarbonization by zinc, it is possible to ensure the production of zinc sublimates and cast stone products and the full neutralization of CO₂. The lowest market potential only for Achisai dump clinker would be around USD 125,600,000 if the cost of commercial clinker sublimates is USD 800/t. The expected net profit would be USD 4,466,039/y. Full article

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. Full article

Illegal solid waste dumping is a significant factor contributing to environmental damage. In this study, 16S rRNA gene sequencing technology was used for the identification and assessment of environmental damage in an illegal dumping area in China, with the aim of confirming environmental damage through analyzing changes in the soil bacterial communities across slag, sewage sludge, and non-contaminated areas. The results indicate that the diversity of soil bacteria decreases with an increase in the degree of pollution. The illegal dumping of slag resulted in an increase in the relative abundance of Firmicutes and a decrease in the relative abundance of Acidobacteriota. Additionally, illegal dumping of sewage sludge resulted in an increase in the relative abundance of Proteobacteria and a decrease in the relative abundance of Acidobacteriota. The contents of Ni and Be in slag and Cu, Pb, and Cd in sewage sludge were key factors affecting bacterial community composition. The results reveal the effects of heavy metal pollution on the soil bacterial community structure and its environmental driving factors, thus expanding understanding in the context of management of the environmental damage caused by illegal dumping, as well as providing a perspective on the changes in the soil bacterial community, allowing for environmental damage confirmation. Full article

Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals and critical raw materials. The historical slags associated with the smelting of polymetallic ores originating from Mississippi Valley-type (MVT) deposits consisted primarily of gypsum. The contemporary slags, obtained from industrial waste rich in zinc and lead, were predominantly spinels (magnesium-aluminate and ferric) that exhibited higher iron content (up to 46.6 wt% of Fe₂O₃) compared to the historical slags (up to 26.1 wt% of Fe₂O₃). The zinc content was similar for both the slag types (3.5 wt% Zn). The average titanium and arsenic contents in the old and contemporary slags were at the same level as well, with 0.21 wt% (Ti) and 0.13 wt% (As), respectively. The contemporary slags contained higher levels of critical raw materials, such as cobalt, nickel, copper, and manganese, compared to the historical slags. Rare earth elements (REEs) were also more abundant in the contemporary slags, with an average content of 212 ppm, while the historical slags averaged 124 ppm. These findings underscore the potential for recovering valuable metals and critical raw materials from such slags, presenting opportunities for resource optimisation and environmental management. Full article

Sewage sludge, also referred to as biosolids, consists of the by-products of wastewater treatment, which are a mixture of the water and organic and inorganic materials eliminated from wastewater sourced from domestic sewage industries during physical, biological, and/or chemical treatments. Biosolids are nutrient-rich organic materials resulting from the treatment of domestic wastewater in treatment plants. Sewage sludge can be considered a significant biological resource for sustainable agriculture. A new composite has been made consisting of soil, sewage sludge collected from the Galati Wastewater Treatment Plant, and slag from the Galati Steel Plant. This study aimed to investigate the structural, morphological, and chemical parameters of this composite through FTIR, SEM-EDX analysis, and XRF analysis. The samples had values of potential toxic elements that were within normal limits according to Directive 86/278/CEE, and, in terms of the iron-to-calcium ratio (I/C), all samples were of a low grade. This is the first time that slag has been added in a sewage sludge–soil combination, which can be an effective fertilizer replacement. Sewage sludge contains substantial amounts of organic matter, and slag reduces the contents of potentially toxic elements. In addition to these attributes, they may provide an opportunity for the beneficial re-use of sewage sludge and slag as resources in agriculture. Full article

This study presents the results of the enlarged laboratory research on the melting of calcined composite pellets for ferrochrome obtained from fine-dispersed conditioned chrome concentrate containing 50.3% Cr₂O₃. This is a product of the gravitational beneficiation of waste sludge tailings from the Dubersay tailings dump at the Donskoy Mining and Processing Plant (DMPP) of JSC “TNC Kazchrome”. The composition of the charge for obtaining composite pellets consisted of 88.5% of chrome concentrate, 3% of mineral part of refined ferrochrome slag (RFC), 4% of ferruginous diatomite, 3% of coke and 1.5% of liquid glass. The initial charge was pelletized on a laboratory pelletizer to a size of 6–10 mm, dried at room temperature for 24 h and fired at 1200 °C for 60 min at a heating rate of 15 deg/min. On the basis of the developed composite annealed pellets, studies on the production of high-carbon ferrochrome at different melting temperatures were carried out. The results showed that with an increase in temperature from 1750 to 1850 °C, the iron–chromium phase in the composition of the alloy increases from 45.2 to 50.1%, the chromium carbide phase decreases from 23.7 to 11.3% and the chromium–iron phase increases from 7 to 11.2%. The carbon content in the alloys at temperatures from 1750 to 1850 °C varies from 7.2 to 8.94%, respectively. The maximum chromium content of the alloy is 64.82% with a melting point of 1850 °C; this alloy can be classified as FeCr60C90LP grade ferrochrome according to the international Chinese standard, which has no more than 0.03% phosphorus and no more than 0.1% sulfur. Full article

This work proposes an environmentally safe and economically feasible method of waste copper-nickel production slag utilization (Kola Mining-Metallurgical Company, Nornickel, Kola Peninsula, Russia). This process involves the decomposition of slag by diluted solutions of sulfuric acid (7–10 wt.% H₂SO₄) with a transfer in a solution of more than 70% silicon, 77% iron and 78% magnesium, and a concentration of non-ferrous metals in the residue (~70%). Copper ions were used in the leaching stage to prevent the release of hydrogen sulfide into the working atmosphere. Dehydration of the solution, followed by washing of water-soluble sulphates from silica, was carried out to separate silica from the leaching solution. The dehydration temperature effect on the silica structural characteristics was determined. The possibility of recovering non-ferrous metals from solutions after silica extraction by precipitation, in the form of copper cementite, and the sum of nickel and cobalt sulfides, was evaluated. Pigment-grade iron dioxide, magnesium sulphate and aluminium hydroxide were obtained by dehydration of the solution after extraction of base metals, calcination and other operations. Sulfuric acid leaching resulted in the disclosure of sulfide grains encapsulated in ferrosilicate, which is a favorable factor for flotation. The depleted residue can be successfully used in the construction industry. Full article

In the aluminum industry, one of the most sensitive economic and environmental problems is the management of resulting waste such as slag, ash and sludge, which become potential sources of pollution. Red sludge, which results from the aluminum industry, is a mixture made up of different forms of iron and aluminum oxides, sodium and aluminum silicates, various titanium compounds, constituted in the residue left after the alkaline solubilization of alumina. The Purpose of this research is to quantify the environmental aspects involved in the storage of sludge in a landfill that has an area of 381,189 square meters and is located in the hearth of a former ballast tank in the western industrial area of the town of Oradea, Romania. The objective of the research was to determine the impact of red sludge dumps, which originated from industrial activity, on the soil and groundwater. The degree of degradation of the soil cover was highlighted by analyzing a number of 12 soil samples (4 collection points, at 3 depths). A total of 14 samples (7 samples on 2 depths) were investigated to monitor the migration mode of the sludge in the structure of the dam. In order to monitor the quality of groundwater, samples from 3 observation boreholes were analyzed. Soil monitoring results did not indicate values of the analyzed parameters above the values imposed by the national legislation on soil quality. Since the dumps were not waterproofed, the quality parameters of the water from the observation boreholes were exceeded, and gravity caused the water to drain into the underground water network in the area. Based on the samples from the observation boreholes, several measurements exceeded allowable values: pH values of the water sample taken from upstream of the dump exceeded the value limits by about 7%, and both upstream and downstream, water samples indicate an excess of 13.60% in the aluminum indicator, 267% in the sulfate ion, and 417% in the sodium ion. This shows a risk of pollution which requires additional monitoring. Full article

The industrial pollution caused by metallurgical waste accumulation has a negative impact on the three environmental factors: soil, air and water. Therefore, the correct management of these wastes would lead to: protection of the environmental factors, the saving of natural resources and sustainability of the steel industry. The purpose of this paper is to assess the chemical and mineralogical compositions of metallurgical wastes landfilled in the Păgida slag dump (Alba County, Romania), for sustainability of the steel industry and metal conservation. The chemical compositions of the two waste samples were analyzed by the XRF (X-ray fluorescence) technique. According to the chemical characterization, magnesium oxide (MgO) has potential to be used as an additional and raw material in the cement industry. The presence of oxides such as CaO, SiO₂ FeO and Al₂O₃ in the compositions of the metallurgical waste samples indicate that they have the potential for use as clinker materials in cement production. The iron and manganese contents from metallurgical wastes can be reused in the iron and steel industry. The presence of V₂O₅ and TiO₂ is connected with the making of stainless steel, and for this reason they have the potential to be reused in the stainless steel industry. The predominant chemical compounds are SiO₂, Fetotal, Cao and MgO. The mineralogical compositions were analyzed by the XRD (X-ray diffraction) technique. The mineralogical compounds presenting reuse potential in different domains are Fayalite, Magnetite, Magnesioferrite and Periclase. The mineralogical compounds from metallurgical wastes can be reused as: raw and/or additional materials in the process from which they originate (steelmaking); raw and/or additional materials in road construction and concrete production; pigments in paints; micronutrients in fertilizers; ore of iron, etc. Then, the theoretical assessments of the recovery potentials of the metals were estimated for slag dumps. Copper (Cu), vanadium (V), molybdenum (Mo) and nickel (Ni) have high recovery potential. The total economic value of the recovery potential of metals from slag dumps was assessed to be USD 1175.7440 million. Full article

Sediment dredging is necessary and vital to preserve maritime activities and prevent floods. The management of these sediments represent an environmental challenge for many countries all over the world. This study focuses on evaluating the feasibility of using dredged sediments for the manufacturing of compressed earth blocks (CEB). The alternative construction material has the potential of reducing the need for dredged sediment onshore storage or ocean dumping. Several experimental tests have been conducted on two geopolymer types, which were obtained by mixing sediments from the northern region of France, fly ash (FA), and grounded blast furnace slag (GBFS). The geopolymers, which were activated using an eight-molar concentrated sodium hydroxide solution (NH), were cured at a temperature of 50 °C. The results have shown that a geopolymer content of 36% of FA and 10% of GBFS along with (NH) alkaline solution has significantly improved the mechanical properties of CEBs, which have outperformed those of Portland Cement-stabilized traditional blocks. The use of NH has resulted in the formation of crystalline calcium silicate hydrate (C-S-H) amorphous gel. Adding GBFS to the mix has enhanced the geopolymer paste compressive strength and microstructure because of the formation of additional C-S-H. The valorization of dredged sediments in CEB based on geopolymer stabilization can contribute to the reduction of the CO₂ footprint of the construction industry. Full article