Search Results (261)

Sustainability in the construction sector has become a fundamental objective for mitigating escalating environmental challenges; given that concrete is the most widely used man-made material, extending its service life is therefore critical. Among durability concerns, magnesium sulfate (MgSO₄) attack is particularly deleterious to concrete structures. Therefore, this study investigates the short- and long-term performance of concrete produced with copper slag (CS)—a massive waste generated by copper mining activities worldwide—employed as a supplementary cementitious material (SCM), together with recycled coarse aggregate (RCA), obtained from concrete construction and demolition waste, when exposed to MgSO₄. CS was used as a 15 vol% cement replacement, while RCA was incorporated at 0%, 20%, 50%, and 100 vol%. Compressive strength, bulk density, water absorption, and porosity were measured after water curing (7–388 days) and following immersion in a 5 wt.% MgSO₄ solution for 180 and 360 days. Microstructural characteristics were assessed using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis with its differential thermogravimetric derivative (TG-DTG), and Fourier transform infrared spectroscopy (FTIR) techniques. The results indicated that replacing 15% cement with CS reduced 7-day strength by ≤10%, yet parity with the reference mix was reached at 90 days. Strength losses increased monotonically with RCA content. Under MgSO₄ exposure, all mixtures experienced an initial compressive strength gain during the short-term exposures (28–100 days), attributed to the pore-filling effect of expansive sulfate phases. However, at long-term exposure (180–360 days), a clear strength decline was observed, mainly due to internal cracking, brucite formation, and the transformation of C–S–H into non-cementitious M–S–H gel. Based on these findings, the combined use of CS and RCA at low replacement levels shows potential for producing environmentally friendly concrete with mechanical and durability performance comparable to those of concrete made entirely with virgin materials. Full article

This study investigates the effects of sodium sulfate (Na₂SO₄) dosage, reaction temperature, and processing time on the structural decomposition of complex compounds in copper slag. Experimental results demonstrated that applying 20% Na₂SO₄ achieves an impressive decomposition rate of 89%, highlighting its effectiveness in liberating valuable metals from the slag matrix. The optimal temperature for maximizing fayalite decomposition is determined to be 900 °C, which significantly enhances reaction kinetics and efficiency. Furthermore, extending the reaction time to 90 min resulted in the highest observed decomposition efficiency. Subsequent leaching experiments in sulfuric acid confirmed that the liberated metal transitioned into the solution phase was very effective, ensuring high metal recovery rates. The treated samples demonstrated metal recovery rates of 97% for copper (Cu), 96% for iron (Fe), and 93% for zinc (Zn). In contrast, the untreated samples exhibited considerably lower recovery rates, with copper at 61%, iron at 59%, and zinc at 65%. Additionally, this approach mitigates filtration challenges by preventing the formation of silica gel. These findings provide key operational parameters for optimizing metal recovery from copper slag and establish a solid foundation for advancing sustainable and efficient resource extraction research. Full article

The metallurgical industry is integral to industrial development. As technology advances and industrial demand grows, the annual output of metallurgical waste slag continues to rise. Combined with the substantial historical stockpile, this has made the utilization of metallurgical slag a new research focus. This study comprehensively sums up the composition and fundamental characteristics of metallurgical waste slag. It delves into the application potential of non-ferrous metal smelting waste slag, such as copper slag, nickel slag, and lead slag, in both sensible and latent heat storage. In sensible heat storage, copper slag, with its low cost and high thermal stability, is suitable as a storage material. After appropriate treatment, it can be combined with other materials to produce composite phase change energy storage materials, thus expanding its role into latent heat storage. Nickel slag, currently mainly used in infrastructure materials, still needs in-depth research to confirm its suitability for sensible heat storage. Nevertheless, in latent heat storage, it has been utilized in making the support framework of composite phase change materials. While there are no current examples of lead slag being used in sensible heat storage, the low leaching concentration of lead and zinc in lead slag concrete under alkaline conditions offers new utilization ideas. Given the strong nucleation effect of iron and impurities in lead slag, it is expected to be used in the skeleton preparation of composite phase change materials. Besides the aforementioned waste slags, other industrial waste slags also show potential as sensible heat storage materials. This paper aims to evaluate the feasibility of non-ferrous metal waste slag as energy storage materials. It analyses the pros and cons of their practical applications, elaborates on relevant research progress, technical hurdles, and future directions, all with the goal of enhancing their effective use in heat storage. Full article

The processing of metallurgical slags is an urgent task, as they contain residual amounts of precious and non-ferrous metals such as gold, silver, copper and zinc. The efficiency of extraction of these metals directly depends on the granulometric composition of the processed material, which determines the need for its detailed analysis. The purpose of this study is to analyze the effect of the granulometric composition of slags on the efficiency of extraction of non-ferrous metals using the flotation method. For this purpose, studies were carried out, including granulometric analysis, chemical composition analysis and flotation tests using Na₂S, KAX and 3418A reagents. The analysis showed that the main part of the slag consisted of particles less than 3.36 mm, while the content of copper was 0.60%, zinc was 2.37%, gold was 0.1 g/t and silver was 7.2 g/t. Flotation experiments confirmed that the use of Na₂S and 3418A increased the recoverability of copper and zinc, and reducing the particle size to d80 <10 microns increased the efficiency of copper extraction by 7%. Thus, the optimization of flotation processes and the control of granulometric composition make it possible to increase the efficiency of metallurgical waste processing, reduce losses of valuable metals and reduce the environmental burden. Full article

The increasing demand for sustainable energy and clean water has prompted the exploration of alternative solutions to reduce reliance on fossil fuels. In this context, hydrogen production through water electrolysis powered by solar energy presents a promising pathway toward a zero-carbon footprint. This study investigates the potential of copper slag, an abundant industrial waste, as a low-cost electrocatalyst for the hydrogen evolution reaction (HER) in contact with saline water such as 0.5 M NaCl and seawater, comparing the electrochemical response when in contact with geothermal water from El Tatio (Atacama Desert). The physicochemical characterisation of copper slag was performed using XRD, Raman, and SEM-EDS to determine its surface properties. Electrochemical evaluations were conducted in 0.5 M NaCl and natural seawater using polarisation techniques to assess the corrosion behaviour and catalytic efficiency of the copper slag electrodes. The results indicate that copper slag exhibits high stability and promising HER kinetics, particularly in seawater, where its mesoporous structure facilitates efficient charge transfer processes. The key novelty of this manuscript lies in the direct revalorisation of untreated copper slag as a functional electrode for HER in real seawater and geothermal water, avoiding the use of expensive noble metals and aligning with circular economy principles. This innovative combination of recycled material and natural saline electrolyte enhances both the technical and economic viability of electrolysis, while reducing environmental impact and promoting green hydrogen production in coastal regions with high solar potential. This research contributes to the value of industrial waste, offering a viable pathway for advancing sustainable hydrogen technologies in real-world environments. Full article

The metallurgical industry has been constantly changing over the past decades. On the one hand, there has been the modernization and improvement of production efficiency, and on the other hand, we have seen a reduction in the negative impact on the environment. The possibility of using alternative materials and the circular economy is significant in this area. In the present work, research was carried out to determine the usefulness of biomass in the form of fruit seeds for the recycling processes of metal-bearing raw materials, including slags from copper production processes, which are characterized by a much higher metal content than ores of this metal. The main carbon-bearing material/reducer used in the process is metallurgical coke. The transformation of the European metal industry has been observed in recent years. To carry out the physicochemical characterization of the tested material, a research methodology was adopted using tools to determine the stability of behavior at high temperatures, chemical composition, and volatile components. Thermodynamic analysis was carried out, indicating the theoretical course of reactions of individual system components and thermal effects, allowing a determination of whether the assumed reactions are endothermic or exothermic. The planned research ends with the reduction process in conditions similar to those carried out in industrial conditions. Enforced by the guidelines for reducing CO₂ emissions, it contributes to a significant reduction in the demand for coke. This paper addresses the issue of determining the feasibility of using selected bioreducers, including cherry stones, to verify their suitability in the process of reducing copper oxides. The study used copper slag with a composition similar to slags generated at the copper production stage in a flash furnace. The results obtained in reducing copper content above 98 wt. % indicate the great potential of this type of bioreducer. It should be noted that, unlike conventional fossil fuels, the use of cherry stones to reduce copper slag can be considered an environmentally neutral method of carbon offset. The resulting secondary slag is a waste product that can be stored and disposed of without harmful environmental effects due to its low lead content. An additional advantage is the relatively wide availability of cherry stones. Full article

Facing sand and gravel shortages, construction waste accumulation, and the “double carbon” goals, improving the performance of recycled aggregate concrete (RAC) and utilizing mineral waste slag are key to the development of green, low-carbon building materials. To enhance the mechanical performance of RAC and facilitate the sustainable utilization of mineral waste, this study innovatively incorporated copper slag (CS), ground granulated blast furnace slag (GGBS), and basalt fiber (BF) into RAC. The modified RAC’s compressive, split tensile, and flexural strengths were systematically investigated. Experimental results indicated that incorporating appropriate amounts of CS or GGBS as single admixtures could effectively enhance the mechanical properties of RAC, with 20% (w) GGBS showing the most pronounced improvement. Compared with RAC, its 28 d compressive strength, split tensile strength and flexural strength were improved by 21.3%, 9.7% and 8.1%, respectively. As opposed to single admixture, 10% CS + 10% GGBS admixture can further improve the mechanical properties of recycled concrete. Compared with RAC, its 28 d compressive strength, split tensile strength, and flexural strength were improved by 25.6%, 29.7%, and 16.6%. The study also showed that 0.2% BF admixed on top of 10% CS + 10% GGBS could still significantly improve the mechanical properties of recycled concrete, and its 28 d compressive strength, split tensile strength, and flexural strength were improved by 31.3%, 35.9%, and 31.2%, compared with RAC, respectively. By XRF, SEM, and EDS techniques, the underlying mechanisms governing the mechanical behavior of RAC were elucidated from the microscale perspective of basalt fiber and industrial waste residues. These findings provide a solid theoretical foundation and a viable technical pathway for the widespread application of recycled aggregate concrete in civil engineering projects. Full article

Cobalt ore resources are relatively scarce; thus, the recycling of cobalt-containing slag is highly significant in the economy and society. In this study, the effects of reduction temperature, the reduction agent ratio, reduction time, and particle size on the grade and recovery rate of cobalt in a concentrate were systematically investigated during the carbothermal reduction of cobalt-containing slag. The results revealed that the grades of cobalt, iron, and copper in the concentrate after magnetic separation were 4.02%, 2.48%, and 81.33%, respectively, and the recoveries were 94.17%, 74.80%, and 53.27%, respectively, under the reduction temperature of 1150 °C, the reduction agent ratio of 40%, the reduction time of 2 h, and the particle size of −3.0 mm. Furthermore, through static reduction roasting in a muffle furnace and dynamic reduction roasting in a rotary kiln followed by magnetic separation, a stable cobalt grade, high selective recovery, and effective enrichment were achieved under optimal conditions. Full article

To address the low resource utilization of copper tailings and high environmental impact of conventional river sand, this study innovatively integrates Box–Behnken design (BBD) with fractal theory to systematically investigate the performance optimization mechanisms of cement mortar incorporating copper tailings sand. A three-factor interaction model was developed through BBD experimental design, considering water–cement ratio (0.38–0.48), replacement ratio (10–30%), and binder–sand ratio (0.3–0.4), to elucidate the macroscopic performance evolution under multiparameter coupling effects. Fractal dimension analysis was employed to quantitatively characterize microstructural evolution. Experimental results demonstrate that the optimal parameters (water–cement ratio: 0.43, replacement ratio: 20%, binder–sand ratio: 0.35) yield superior performance, with 28-day compressive/flexural strengths reaching 61.88/7.14 MPa (12.3%/9.8% enhancement over the control group), and sulfate attack resistance showing 0.74% mass loss after 30 cycles. Microstructural analysis reveals reduced fractal dimension (D = 2.31) in copper tailings-modified specimens, indicating improved pore structure homogeneity. The enhanced performance is attributed to synergistic effects of micro-aggregate filling and pozzolanic reaction-driven C-S-H gel densification. This research establishes a novel multiscale methodology overcoming the limitations of conventional single-factor analysis, providing theoretical and technical support for high-value utilization of industrial solid wastes in construction materials. Full article

Chloride ions in zinc refining accelerate equipment corrosion and anode and cathode losses, increase lead content, and reduce zinc quality. Therefore, the removal of chloride ions has become a research priority. The existing copper slag dechlorination process has problems such as the solid film barrier leading to impeded mass transfer, product wrapping triggering active site coverage, and incomplete reactions due to insufficient reaction-driving force, leading to low utilization of copper slag, poor dechlorination efficiency, and long reaction times. To address these issues, a new method of deep dechlorination based on the reduction of Cu²⁺ by liquid-phase mass transfer is proposed in this paper. The process utilizes ascorbic acid as a reducing agent, establishes a homogeneous aqueous phase reaction system, breaks through the solid membrane barrier, and avoids the encapsulation of the product layer, achieving efficient dechlorination. The enol structure of ascorbic acid promotes rapid dechlorination through proton-coupled electron transfer (PCET). Thermodynamic calculations show that compared to the current copper slag dechlorination process, this method increases the reaction-driving force by 18.6%, reduces the Gibbs free energy (ΔG^θ) by 59.3%, and increases the equilibrium constant by 6.7 × 10⁹ times, making the reaction more complete and achieving a higher degree of purification. The experimental results show that under optimized conditions, the chloride ion concentration in the solution decreases from 1 g/L to 0.0917 g/L within 20 min, with a removal rate of 90.8%. The main precipitate is CuCl. This process provides a more efficient solution to the chloride ion contamination problem in the hydrometallurgical zinc refining process. Full article

The research focuses on the management of oxygen lance copper tip rotation to mitigate wear on the MgO–C refractory lining in the basic oxygen furnace (BOF). This study investigates the continuous increase in the consumption of gunning mixture throughout the BOF campaign, particularly in the trunnion area. Clear trends in refractory thickness reduction were observed, with two significant wear phases identified: between heats 1000–7000 and between heats 11,000–16,000. These phases correlate with increased gunning mixture consumption. The most significant wear was found between 4–5.2 m height, known as the trunnion area. The study proposes turning of the oxygen lance copper tip (jet) during its replacement to distribute refractory lining wear more evenly and reduce gunning mixture consumption. A detailed analysis of the gunning mixture consumption during whole campaign as well as laser measurements of the working lining profile confirmed localized wear in areas of the trunnions that were excessively exposed by the direct impact of the pure oxygen jet stream and the sprayed and spitted emulsion of molten metal and slag. This position management strategy, coupled with slag splashing and high-basic slag coating, can reduce trunnion area gunning mixture usage and promote uniform MgO–C lining wear. Full article

This study proposes a synergistic treatment method for BOF slag and copper slag via oxidation–magnetic separation, with the dual goals of preparing MgFe₂O₄ magnetic material and stabilizing the non-magnetic slag. The effects of copper slag addition, the oxidation temperature and the oxidation time on the phase transformation and MgFe₂O₄ morphology during the oxidation process are investigated. The results show that copper slag addition can release the simple iron oxides of FeO and Fe₂O₃ from iron-containing phases from BOF slag and copper slag, promoting the synthesis of MgFe₂O₄. Furthermore, the oxidation temperature and oxidation time have a significant influence on the size of the MgFe₂O₄ particles. To obtain the MgFe₂O₄ magnetic material, the optimum oxidation parameters were used, with an oxidation degree of Fe²⁺ of 95.85% and a yield of MgFe₂O₄ of 90.31%. In addition, the main phase of non-magnetic slag was Ca₂SiO₄, and both free CaO and free MgO from BOF slag were eliminated, indicating a potential application in construction materials. This technology maximizes resource utilization and the valorization of metallurgical solid waste. 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

Copper slag, produced in pyrometallurgical processes, has the potential to generate hydrogen through thermolysis, depending on its composition. This manuscript explores the use of copper slag as a highly abundant and low-cost material for thermochemical water splitting using concentrated solar power. Copper slag can undergo endothermic reactions with water vapor at high temperatures, conditions which are favorable for activating hydrogen evolution reactions which can be a potential resource for metal recovery such as magnetite and hematite in the circular economy. While research on copper slag and its components has primarily focused on the recovery of valuable metals and material reuse, its direct application in hydrogen production remains largely unexplored, partly due to historically low interest in hydrogen as an energy source. The vast deposits of copper slag in the Atacama Desert, combined with the growing demand for renewable energy, present a unique opportunity to develop sustainable and cost-effective hydrogen production technologies. Full article

Copper-containing sludge and spent petrochemical catalyst (SPC) were investigated for recovering palladium (Pd) and silver (Ag). Increasing the mixing ratio of alumina-based SPC leads to reduced recovery rates at 1500 °C. Specifically, as the SPC mixing ratio increases from 10% to 30%, the recovery rate of Pd and Ag sharply decreases to 62.1% and 91.0%, respectively. This is attributed to an increase in the slag viscosity as well as to the higher sulfur content in the metal phase by decreasing the CaO/Al₂O₃ ratio of the slag. An increase in the slag viscosity causes a decrease in the metal recovery, as it lowers the settling velocity of metal droplets, resulting in imperfect metal separation, i.e., an increase in physical loss. Additionally, the presence of sulfur at the slag–metal interface was found to reduce interfacial tension, facilitating the entrapment of copper droplets within the slag. This further hindered phase separation and contributed to an increase in physical loss. This study highlights that physical loss is more serious in metal recovery rather than chemical loss, which is dependent on the thermochemical solubility of the target metals in the slag. The results emphasize the need for the precise control of slag properties to maximize the metal recovery processes in conjunction with a mitigation of CO₂ emissions. Full article