Search Results (169)

Background: Gold mining is a critical part of the industry of Central Asia, contributing significantly to regional economic growth. However, gold production management faces numerous challenges, including adopting innovative technologies such as AI, using improved logistical equipment, resolving supply chain inefficiencies and disruptions, and incorporating modernized waste management and advancements in gold bar processing technologies. This study explores how advanced technologies and improved logistical processes can enhance efficiency and sustainability. Method: This paper examines gold production processes in Kyrgyzstan, a gold-producing country in Central Asia. The case study approach combines qualitative interviews with industry stakeholders and a system dynamics (SD) simulation model to compare current operations with a technology-based scenario. Results: The simulation model shows improved outcomes when innovative technologies are applied to ore processing, waste refinement, and gold bar production. The results also indicate an approximate twenty-five percent reduction in transport time, a thirty percent decrease in equipment downtime, a thirty percent reduction in emissions, and a fifteen percent increase in gold extraction when using artificial intelligence, smart logistics, and regional smelting. Conclusions: The study concludes with recommendations to modernize equipment, localize processing, and invest in digital logistics to support sustainable mining and improve operational performance in Kyrgyzstan’s gold sector. Full article

Iron-rich bauxite residue (red mud) is a hazardous alkaline solid waste produced during the production of alumina from high-iron bauxite, which poses severe environmental challenges due to its massive stockpiling and limited utilization. In this study, metallic iron was recovered from high-iron red mud using the smelting reduction process. Thermodynamic analysis results show that an increase in temperature and sodium oxide content, along with an appropriate mass ratio of Al₂O₃ to SiO₂ (A/S) and mass ratio of CaO to SiO₂ (C/S), contribute to the enhancement of the liquid phase mass fraction of the slag. During the smelting reduction process of high-iron red mud, iron recoveries for low-alkali high-iron red mud and high-alkali high-iron red mud under optimal conditions were 98.14% and 98.36%, respectively. The metal obtained through reduction meets the industrial standard for steel-making pig iron, which is also confirmed in the pilot-scale experiment. The smelting reduction process of high-iron red mud can be divided into two stages, where the reaction is predominantly governed by interfacial chemical reaction and diffusion control, respectively. The apparent activation energy of high-alkali high-iron red mud is lower than that observed for low-alkali high-iron red mud. The reduced slag can be used as a roadside stone material or cement clinker. This proposed method represents a sustainable process for the comprehensive utilization of high-iron red mud, which also promotes the minimization of red mud. 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

Red mud, a highly alkaline industrial by-product generated during aluminum smelting, poses serious environmental risks such as soil alkalization and ecological degradation. In this study, response surface methodology (RSM) was integrated with advanced microstructural characterization techniques to optimize the performance of red mud–slag composite cementitious materials through multi-factor analysis. By constructing a four-factor interaction model—including red mud content, steel fiber content, alkali activator dosage, and calcination temperature—a systematic mix design and performance prediction framework was established, overcoming the limitations of traditional single-factor experimental approaches. The optimal ratio was determined via multi-factor RSM analysis as follows: the 28-day flexural strength and compressive strength of the specimens reached 12.26 MPa and 69.83 MPa, respectively. Furthermore, XRD and SEM-EDS analyses revealed the synergistic formation of C-S-H and C-A-S-H gels, and their strengthening effects at the fiber–matrix interfacial transition zone (ITZ), elucidating the micro-mechanism pathway of “gel densification–rack filling–strength enhancement.” This work not only enriches the theoretical foundation for the design of red mud-based binders but also offers practical insights and empirical evidence for their engineering applications, highlighting substantial potential in the development of sustainable building materials and high-value utilization of industrial solid waste. 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

Red mud from bauxite processing is among the large-tonnage technogenic waste that poses a significant ecological threat. At the same time, red mud serves as a raw material source for expanding the resource base for obtaining iron, rare metals, and rare earth elements. Numerous studies on their utilization have shown that only through comprehensive processing, combining pyrometallurgical and hydrometallurgical methods, is it possible to maximize the extraction of all the useful components. This work addresses the first stage of a comprehensive technology for processing red mud through reduction smelting, separating iron in the form of pig iron, and producing slag. Studies were conducted on the reductive smelting of red mud using waste slurry from alumina production as the calcium-containing material, taken in proportions calculated to obtain a fluid slag with a hydraulic modulus of 0.55–0.8. The permissible mixing range of red mud with waste slurry was determined to be in the ratio of 0.56–1.2. In cases where the charge was prepared in violation of the required hydraulic modulus value, pig iron was not obtained during smelting. When the hydraulic modulus requirement was met, the temperature of the reductive smelting process was 1350–1400 °C. The total amount of recovered iron obtained as pig iron and fine fractions amounted to 99.5% of the original content. The low iron content (0.23–0.31%) in the non-magnetic slag fraction allows for the production of high-quality titanium oxide and rare earth element concentrates in the subsequent stages of the comprehensive hydrometallurgical processing of red mud, involving acid leaching. Based on the results of a phase analysis of the slag, pig iron, and melt, the reactions of the reductive smelting process were established, and their thermodynamic likelihood was determined. In fluid slags, the content of the sodium aluminosilicate phase is twice as high as that in slag with a higher hydraulic modulus. The reductive smelting of 100% red mud with the addition of calcium oxide, calculated to achieve a hydraulic module of 0.55 at a temperature of 1350–1400 °C, produced pig iron and slag with high alkali and iron contents. Full article

Systematic assessment of heavy metal contamination in agricultural soils is critical for addressing ecological and public health risks in industrial-intensive cities like Lanzhou, with direct implications for achieving UN Sustainable Development Goals (SDGs) 2 (Zero Hunger), 15 (Life on Land), and 3 (Good Health). The present study evaluates farmland soils around six industrial sectors: waste disposal (WDZ), pharmaceutical manufacturing (PMZ), chemical manufacturing (CMZ), petrochemical industry (PIZ), metal smelting (MSZ), mining (MZ) and one sewage-irrigated zone (SIZ) using geo-accumulation index, Nemerow composite pollution index, potential ecological risk index, and health risk models. The following are the major findings: (1) SIZ and PMZ emerged as primary contamination clusters, with Hg (I_geo = 1.89) and Cd (I_geo = 0.61) showing marked accumulation. Chronic wastewater irrigation caused severe Hg contamination (0.97 mg·kg⁻¹) in SIZ, where 100% of the samples reached strong polluted levels according to the Nemerow composite pollution index; (2) Hg and Cd dominated the ecological risks, with 41.32% of the samples exhibiting critical Hg risks (100% in PMZ and SIZ) and 32.63% showing strong Cd risks; and (3) oral ingestion constituted the dominant exposure pathway. Children faced carcinogenic risks (CR = 1.33 × 10⁻⁴) exceeding safety thresholds, while adult risks remained acceptable. Notably, high Hg and Cd levels did not translate to proportionally higher health risks due to differential toxicological parameters. The study recommends prioritizing Hg and Cd control in PMZ and SIZ, with targeted exposure prevention measures for children. Full article

Amid escalating global climate crises and the urgent imperative to meet the Paris Agreement’s carbon neutrality targets, the steel industry—a leading contributor to global greenhouse gas emissions—confronts unprecedented challenges in driving sustainable industrial transformation through innovative low-carbon steelmaking technologies. This paper examines decarbonization technologies across three stages (source, process, and end-of-pipe) for two dominant steel production routes: the long process (BF-BOF) and the short process (EAF). For the BF-BOF route, carbon reduction at the source stage is achieved through high-proportion pellet charging in the blast furnace and high scrap ratio utilization; at the process stage, carbon control is optimized via bottom-blowing O₂-CO₂-CaO composite injection in the converter; and at the end-of-pipe stage, CO₂ recycling and carbon capture are employed to achieve deep decarbonization. In contrast, the EAF route establishes a low-carbon production system by relying on green and efficient electric arc furnaces and hydrogen-based shaft furnaces. At the source stage, energy consumption is reduced through the use of green electricity and advanced equipment; during the process stage, precision smelting is realized through intelligent control systems; and at the end-of-pipe stage, a closed-loop is achieved by combining cascade waste heat recovery and steel slag resource utilization. Across both process routes, hydrogen-based direct reduction and green power-driven EAF technology demonstrate significant emission reduction potential, providing key technical support for the low-carbon transformation of the steel industry. Comparative analysis of industrial applications reveals varying emission reduction efficiencies, economic viability, and implementation challenges across different technical pathways. The study concludes that deep decarbonization of the steel industry requires coordinated policy incentives, technological innovation, and industrial chain collaboration. Accelerating large-scale adoption of low-carbon metallurgical technologies through these synergistic efforts will drive the global steel sector toward sustainable development goals. This study provides a systematic evaluation of current low-carbon steelmaking technologies and outlines practical implementation strategies, contributing to the industry’s decarbonization efforts. Full article

The swift advancement of China’s mining sector has led to the generation of substantial amounts of industrial solid waste, which poses significant risks to the ecological environment. This study aims to investigate effective methods for utilizing industrial solid waste in the production of mine filling materials, thereby facilitating green mine construction and the efficient use of resources. The study employs the PRISMA methodology to conduct a systematic review of the pertinent literature, analyzing the current status, challenges, and developmental trends associated with the use of coal-based solid waste, smelting waste, industrial by-product gypsum, and tailings in filling materials. The findings indicate that, while the use of individual coal-based solid waste in filling materials shows promise, there is a need to optimize the ratios and activation technologies. Furthermore, the synergistic application of multi-source coal-based solid waste can enhance the overall utilization rate; however, further investigation into the reaction mechanisms and ratio optimization is required. Smelting slag can serve as a cementing agent or aggregate post-treatment, yet further research is necessary to improve its strength and durability. Industrial by-product gypsum can function as an auxiliary cementing material or activator, although its large-scale application faces significant challenges. Tailings present advantages as aggregates, but concerns regarding their long-term stability and environmental impacts must be addressed. Future research should prioritize the synergistic utilization of multi-source solid waste, performance customization, low-carbon activation technologies, and enhancements in environmental safety. Additionally, the establishment of a comprehensive lifecycle evaluation and standardization system is essential to transition the application of industrial solid-waste-based filling materials from empirical ratios to mechanism-driven approaches, ultimately achieving the dual objectives of green mining and the resource utilization of solid waste in mining operations. Full article

This study explored the feasibility of the carbon-free smelting of ferrochrome (FeCr) using a complex reducing agent—ferroaluminosilicalcium alloy (FeAlSiCa)—produced from industrial waste and ferrosilicochrome (FeSiCr) dust. Laboratory-scale smelting experiments were conducted with Cr concentrate and the addition of FeAlSiCa and FeSiCr dust under four different reducing agent contents: (1) 10% deficiency, (2) stoichiometric amount, (3) 10% excess, and (4) 20% excess. It was found that with a 10% excess, a nearly complete reduction of Cr₂O₃ was achieved (residual content in slag ≤ 0.9%), resulting in the formation of low-carbon FeCr (LC FeCr) with a high nitrogen content (up to 2.6%). Based on a thermodynamic analysis of the reduction reactions, the high reactivity of the FeAlSiCa and FeSiCr components (Ca, Al, and Si) at 1500 °C was confirmed. These reactions were exothermic, which demonstrates the energy efficiency of using these ferroalloys as reducing agents in FeCr smelting. The resulting slag is structurally stable and does not disintegrate over time, making it a promising candidate for potential reuse as a secondary raw material. The results demonstrate the promise of the proposed technology for both reducing the carbon footprint of ferroalloy production and lowering the cost of the metallothermic production of LC FeCr. Full article

Arsenic-containing acidic wastewater from nonferrous heavy smelting industry is a dangerous source of arsenic pollution due to its complex composition, high acidity, and strong toxicity. In this study, an environment-friendly strategy was proposed, in which highly stable scorodite was synthesized in acidic wastewater. The effects of initial pH, Fe/As molar ratio, and oxidation-reduction potential (ORP) on the morphology, particle size, phase composition, and leaching stability of scorodite were systematically investigated. The results demonstrate a distinct morphological evolution with increasing pH. The products were transitioned from bone-shaped to rice grain-shaped, and then turned to bipyramidal polyhedral-shaped and amorphous aggregates. When the Fe/As molar ratio was increased, the scorodite crystallization quickly formed well-defined particles (the size was 15–20 μm). Higher ORP values led to progressively irregular morphologies, reduced particle sizes, and ultimately formed amorphous ferric arsenate. The large-grained scorodite with regular morphology and high leaching stability from high-arsenic solutions (25 g/L) was produced under optimal conditions (initial pH 1.5, Fe/As 1.5, ORP 385 mV). These findings provide critical technical support for arsenic solidification from waste liquids under atmospheric pressure conditions. Full article

This case study is the second of three which we have been conducting on different industrial waste landfills. We are planning a fourth study comparing the three landfills. Phytostabilization, including assisted phytostabilization, is a measure of reducing the negative impact of industrial waste landfills on the environment. It is particularly important in the case of old unprotected and often abandoned landfills. Most studies investigate how phytostability depends on the plant species but do not consider its dependence on the specific location at the landfill where the plants are growing. We assumed that the habitat conditions within the landfill had been modified unequally over the years. The most heterogeneous habitat conditions were found on the slopes of the landfill. The aims of the study were to assess the impact of the location on the landfill, i.e., the site of growth; the impact of the plant species or organ; and the combined and simultaneous impact of the location and species/organ on the phytostabilization of cadmium, lead, zinc, and copper. All bioaccumulation factor (BCF) values calculated for each metal and each location (base, middle, and top) differed statistically significantly from one another. In the case of lead, zinc, and copper the highest BCFs, irrespective of species, were obtained for plants growing at the top of the landfill, whereas the highest value for cadmium was recorded at the base. Additionally, all interactions analyzed between location and species/organ were statistically significant. Variations in the BCF values, including the variation influenced by the interaction between location and species/organ, followed four distinct patterns along the slope of the landfill from the base, to the middle, and to the top. Full article

It is essential to evaluate the prospective development trends of coke dry quenching (CDQ) waste heat power generation, to reduce the comprehensive cost of the steelmaking system. Based on TIMES energy system optimization model, this study develops a model of China’s iron and steel production. Three scenarios are established, predictions and comparisons are conducted regarding the iron and steel production structure, total CDQ quantity, CO₂ and pollutant emissions under these scenarios. The findings indicate that: (1) The advancement of hydrogen metallurgy and EAF scrap smelting facilitates a reduction in the quantity of BF-BOF steelmaking and total CDQ consumption. (2) The decreasing demand for CDQ shows that the shift to clean production alters process pathways and compels the energy system from scale-driven to flexibility-focused. (3) The marginal value of the CDQ system is contingent upon the targeted policy support for multi-energy co-generation systems and their deep integration with hydrogen infrastructure. Accordingly, the utilization of CDQ waste heat power generation should be considered as a transitional strategy, it will be imperative to implement a reduction in capacity. Full article

To address the issues of low solid–liquid mixing and mass transfer efficiency and difficult real-time regulation in the resource utilization of non-ferrous metal smelting slag, this study constructs a research framework integrating Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling models and machine learning. The framework systematically investigates particle motion characteristics and mass transfer laws in stirred tanks and enables an intelligent prediction of key parameters. Through a CFD-DEM two-way coupling simulation, the study quantifies particle dispersion characteristics using relative standard deviation (RSD) and calculates the mass transfer coefficient (k) based on the Hughmark model, revealing the effects of particle size and impeller speed on mixing and mass transfer efficiency. For parameter prediction, particle motion and mass transfer data are used to train a multi-model prediction library, with model performance evaluated through comparative experiments. The results show that increasing the rotational speed shortens the particle mixing time, reduces RSD values by 25–40%, increases the coupling force, and decreases stability during the circulation phase. Different machine learning (ML) algorithms exhibit varying performances in the time-series prediction of particle motion characteristics and real-time prediction of mass transfer coefficients. Notably, GA-BP achieves a fitting degree R of 0.99 in both predictions, meeting the requirements for the structural optimization and intelligent regulation of stirred tanks. This research provides theoretical support and technical pathways for the structural optimization and intelligent control of stirred tanks, offering engineering application value in fields such as hydrometallurgy and solid waste resource utilization. Full article