Non-ferrous metallurgical slags generated during pyrometallurgical smelting of non-ferrous metals cause environmental pollution as a stockpile, but slags also have enormous potentials for waste heat recovery and valuable metal recycling. This paper systematically synthesized common and specific physicochemical characteristics of non-ferrous metallurgical slags. It focused on research progress, core principles, process optimization directions, technical advantages, and application bottlenecks of waste heat recovery technologies for three typical slags (copper slag, ferronickel slag, and lead slag), which were classified into physical methods and chemical methods, and summarized research hotspots and development trends of each technology. Physical methods were centered on synergistic technology of granulation and heat exchange, while chemical methods focused on synergistic recovery of waste heat and resources. Cascaded recovery system integrating the two is the main development direction in the future. This paper provided theoretical reference and technical support for industrial upgrading and green development of waste heat recovery technologies for non-ferrous metallurgical slags.

To address issues of high cost of traditional cement-based filling materials and poor bonding of ultra-fine tailings as a component, a solid-waste-based cementitious material was developed for the backfill of a molybdenum mine in Shaanxi Province. Steel slag, slag, and desulfurization gypsum were used as main raw materials, formulated with a performance modifier. The formulation of the solid-waste-based cementitious material was studied by varying the content and fineness of slag powder. The optimal formulation was selected to investigate application performance of backfill bodies and micromorphology of hydration products of the cementitious material. Results showed that the optimal formula of the solid-waste-based cementitious filling material was 60% slag powder (407 m²/kg), 20% steel slag powder, 20% desulfurization gypsum, and 0.6% performance regulator. Under this ratio, compressive strength of backfill bodies at all curing ages was superior to that of P·O 42.5 cement, with 28-day compressive strength reaching up to twice that of the cement group. Moreover, when cement-sand ratios were 1∶7, 1∶15, and 1∶16, respectively, strength requirements of different backfill zones were satisfied. Meanwhile, the material exhibited excellent fluidity and volume stability. Leaching toxicity indexes of all backfill bodies were lower than the limits specified in GB 8978—1996, indicating favorable environmental safety. Main hydration products were acicular-rod ettringite and fibrous gel-like C-S-H gel, which were interwoven to form a dense structure. The solid-waste-based cementitious filling material developed in this study had potentials of realizing resource utilization of solid waste and reducing backfill costs, providing technical support for green and efficient backfill of mines.

Multi-phase refractory materials were prepared using copper slag tailings and waste high-alumina bricks. Thermodynamic behavior of copper slag tailings during sintering was studied by XRD and TG-MS. Influence of copper slag tailing and waste high-alumina brick content on mechanical properties and high temperature properties of refractory materials were studied. Microstructure and phase transition process of multi-phase refractory materials were studied by SEM-EDS and XRD. Results showed that decomposition product of iron olivine in copper slag tailings reacted in-situ with alumina in waste high-alumina brick, and finally formed a mullite-corundum composite crystal phase combined with Fe-Al intercrystalline phase. When mass fraction of waste high-alumina brick and copper slag tailing was 40% and 10%, respectively, comprehensive performance of refractory material was the best. Compressive strength was 110.4 MPa, refractoriness under load reached 1 399 ℃, and strength retention rate after thermal shock was more than 80%. Research results provided a new prospective for high-value utilization of copper slag tailings and waste high-alumina bricks which are the main solid waste in copper smelting industry.

To achieve large-scale and high-value utilization of copper tailings, copper tailings were compounded with mineral powder and fly ash, and then ground by an ultra-fine ball mill with special grinding media to obtain copper-tailings-based ultrafine composite admixtures with specific surface areas of 755 m²/kg and 730 m²/kg, respectively. Basic properties of these admixtures and their effects on workability, mechanical properties and durability of concrete were studied. Results showed that compared with conventional fineness S95 mineral powder, flow ratio of copper-tailings-based ultrafine composite admixtures was slightly lower, but they had higher early activity. 7-day activity index was increased by 10% and 7%, respectively, and 28-day activity index was slightly lower than that of S95 mineral powder. Addition of fly ash can improve flow ratio and 28-day activity index. In C30 grade concrete, copper-tailings-based ultrafine composite admixtures can completely replace original slag powder in mix proportion and further reduce cement dosage by 20 kg. Compressive strength of the concrete showed an increasing trend. Impermeability, chloride ion penetration resistance, carbonation resistance, sulfate resistance and freeze-thaw resistance of the concrete were all improved. This study provided an effective approach and theoretical support for high-value-added resource utilization of copper tailings.

Copper smelting slag tailings are solid wastes obtained from flotation depletion of copper slag generated in pyrometallurgical copper smelting. Their massive accumulation produces serious environmental and safety hazards. Forsterite-spinel composite materials were prepared by a high-temperature solid-state sintering method using copper smelting slag tailings as the main raw material, with addition of light-burned magnesia and activated alumina. Effects of sintering temperature on phase composition, microstructure, and physical properties of the materials were systematically investigated. Results showed that the main crystalline phases of sintered samples were forsterite and spinel, while fayalite phase was completely decomposed. As sintering temperature increased, grains of forsterite and spinel gradually grew, and densification degree of the material continuously improved. When sintering temperature was 1 400 ℃, the sample exhibited the best comprehensive performance, with a bulk density of 2.75 g/cm³, an apparent porosity of 24.11%, and a cold compressive strength of 138.5 MPa.

Resource utilization of modified metallurgical slag, as an important solution for solid waste disposal in metallurgical industry, shows significant potential for application in wastewater purification and treatment. This paper reviewed research progress on enhancing adsorption and catalytic properties of modified metallurgical slag through physical and chemical modification methods, and systematically analyzed the treatment mechanism and efficiency in treating organic pollutants (e.g., aniline, dyes) and inorganic pollutants (e.g., heavy metals, phosphates). The study showed that the modified metallurgical slag can efficiently remove pollutants from water by virtue of its porous structure, abundant active sites and surface chemical properties, realizing the environmental protection goal of 'treating waste with waste'. The technology had advantages such as low cost, high stability and low risk of secondary pollution, providing an innovative solution for the green transformation of water treatment industry and resource recycling. In the future, it is necessary to further optimize the modification process and to explore strategies for synergistic management of multiple pollutants.

To study the friction and wear properties of CuNi6Sn6 alloy under high-temperature and high-load working condition, an MMU-10G friction-abrasion testing machine was used for experiments, and a LEXT OLS5000 3D confocal laser scanning microscope was utilized to examine the worn surface morphology for determination of wear mechanisms. Under a load of 45 N, friction coefficient of the alloy increased and then decreased with rising ambient temperature. Under a higher load of 75 N, friction coefficient remained relatively stable when ambient temperature was below 150 ℃, but fluctuated significantly at 200 ℃. When the load was increased to 105 N, friction coefficient was only stable below 100 ℃. When ambient temperature was below 150 ℃, wear mass increased with the load. While at 200 ℃, wear mass was relatively large. At lower ambient temperatures, wear mechanism was mainly abrasive wear. As the load increased, it manifested as fatigue pitting and fatigue delamination. Under medium-high temperatures and low loads, adhesive wear predominated; under high temperature and high load, severe plastic deformation and surface burn occurred. When ambient temperature exceeded 150 ℃, wear severity increased. Therefore, CuNi6Sn6 alloy was suitable for service conditions with ambient temperatures below 150 ℃ and loads below 75 N.

Conventional treatment methods for complex copper slags originating from zinc smelting are often constrained by high energy consumption, intricate workflows, and low metal recovery efficiencies. To address these challenges, a streamlined, high-efficiency technology based on cyclone electrowinning was developed. This novel process enabled the synergistic leaching of copper, zinc, and indium while selectively extracting copper, effectively obviating the need for solvent extraction and its associated organic pollution risks. This study specifically investigated electrolytic migration behavior of metal ions—predominantly Cu²⁺—during direct cyclone electrowinning of polymetallic leachates. Utilizing a four-stage stepwise depletion protocol, the process yielded cathode copper with a purity exceeding 99.97% and a current efficiency greater than 97.83%. By significantly simplifying the traditional "leaching-purification-electrowinning" circuit, this technology provided a green, cost-effective pathway for the circular utilization of copper resources from complex polymetallic slags.

The iron and steel industry is a cornerstone of the national economy, yet its production process generates a massive amount of solid waste, among which iron and steel slag is the primary by-product. For a long time, the stockpiling and landfilling of this slag have not only occupied vast land resources but also posed potential threats to the soil, water, and atmosphere due to heavy metal ions in leachate and dispersion of dust. However, steel slag is a secondary resource awaiting development, which is rich in valuable elements such as calcium, silicon, iron, aluminum, magnesium, and manganese, as well as rare metals like vanadium and titanium. Main phases of steel slag include dicalcium silicate, tricalcium silicate, and calcium ferrite. Resourcezation potential of steel slag comes from two aspects. On one hand, technologies such as magnetic separation, gravity separation, or reduction roasting can recover iron and rare metals. On the other hand, high calcium and silicon content endows it with the potential to substitute for natural mineral resources. Achieving efficient recovery of valuable elements from steel slag and comprehensive application of the overall material is crucial for promoting green, circular, and low-carbon development of the iron and steel industry. This review systematically summarized physicochemical properties of steel slag, focusing on technical principles and research progress in recovering major valuable elements like iron, calcium, and silicon, as well as rare elements such as vanadium and titanium. Simultaneously, it comprehensively outlined current status of steel slag utilization in fields such as building materials, environmental remediation, and agriculture. Finally, it analyzed current technological challenges and provided an outlook on future research directions, offering a theoretical reference and technological pathways for high value resources utilization of steel slag.

Alkali residue, a solid waste with potential cementitious properties, poses severe environmental risks when piled in a large amount. To enable large-scale utilization of alkali residue, this study partially replaced cement with alkali residue to prepare alkali residue modified cemented backfill. Dynamic impact tests were conducted to investigate mechanical behavior and energy evolution characteristics of alkali residue modified cemented backfill. Results indicated that incorporation of alkali residue altered the mechanical performance and enhanced compressive strength of the backfill. With increasing alkali residue replacement proportion, compressive strength first increased and then decreased, peaking at an alkali residue replacement proportion of 5%. Energy evolution of alkali residue modified backfill can be categorized into three stages: linear elastic stage, plastic yield stage, and instable failure propagation stage. Addition of alkali residue brought elastic strain energy closer to total input energy during the first stage, reduced instances of negative dissipated energy, and rendered the energy curves more physically realistic. As alkali residue content increased, the maximum elastic strain energy initially rose and then declined, reaching its peak at an alkali residue replacement proportion of 5%. These findings demonstrated that alkali residue improved mechanical performance of cemented backfill, thereby providing a theoretical basis for the application of alkali residue in mine backfilling operations.