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Iron ore tailings (IOTs), specifically those generated from iron ore beneficiation plants, present notable challenges to both the environment and economic sustainability. Recognized as precious secondary resources, IOTs encapsulate recoverable metals such as Cu and Fe, juxtaposed with harmful elements like Pb and Cr, necessitating a meticulous approach towards their recycling and purification to harness potential benefits optimally, as opposed to unprocessed disposal. Although numerous literatures have reviewed the treatment methods of IOTs, this article is distinguished by its provision of a novel evaluative perspective. The chemical and physical properties of iron ore tailings are comprehensively examined in this review, and various beneficiation and metallurgical recovery techniques such as flotation, magnetic separation, leaching, and magnetization roasting are rigorously evaluated. Effective strategies for enhancing the utilization efficiency of IOTs are thereby revealed. Special emphasis is placed on the common technical challenges and developmental bottlenecks encountered in the metallurgical processes, which have seldom been explored in depth in prior studies. In this synthesis, priority is assigned to cultivating a nuanced understanding of the intrinsic challenges and prospective trajectories pivotal to advancing the industrial application of IOTs, propelled by a commitment to fostering environmental integrity and economic viability in mining operations. [Display omitted] • Introduces a unique evaluative approach to IOTs, prioritizing environmental and economic viability in recycling. • Assesses a variety of beneficiation and metallurgical recovery techniques. • Spotlights unexplored technical challenges and advancement strategies for sustainable and efficient IOTs utilization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The limonitic nickel laterite ore is beneficiated by the selective reduction roasting-magnetic separation process. • The mechanism of calcium sulfate and silica in promoting selective reduction of limonitic nickel laterite ore was revealed. • Growth behaviors of ferronickel particles in the reduction roasting process are clarified. Abstract Attempts to economically upgrade low nickel content laterite ore face a number of challenges, including limited ability to beneficiate the ore prior to processing due to its complex association and dissemination structure. Limonitic nickel laterite, characterized by its relatively high iron grade and low nickel content, is very difficult to upgrade. The current work explores improving the beneficiation of nickel from limonitic laterite ore through interaction of silica and calcium sulfate in a selective reduction-wet magnetic separation process. The results show that the ferronickel concentrate assaying 5.0% Ni can be obtained at a nickel recovery of 95.9%, when limonitic laterite ore is reduced at 1250 °C for 60 min with the addition of 3 wt% CaSO 4 , 8 wt% silica and 3 wt% graphite. The mechanism of additives in promoting the selective reduction of nickel laterite ore was also investigated by XRD, VSM, SEM-EDS and EPMA. The silicate reacted with iron oxide to form the liquid, which decreased the iron metallization ratio. S 2 from the thermal decomposition of CaSO 4 in a strong reducing atmosphere significantly promoted γ Fe–Ni particle growth by formation of an Fe-FeS eutectic with a low melting point. [ABSTRACT FROM AUTHOR]

Non-Ferrous Metallurgical Wastes, including copper slag, red mud, jarosite residue, zinc-bearing dust, pyrite cinder, and nickel slag, are hazardous waste products released during the metal extraction process. Metallurgical solid wastes pose significant risks to the environment due to their content of hazardous elements, which may impact the quality of surface water and groundwater. However, the iron content in non-ferrous metallurgical solid wastes such as copper slag, red mud and zinc-containing dust can often reach 30–50%, which is higher than the average iron grade (27%) of the iron ores found in China and has a high utility value. In this manuscript, we summarize the primary optimization process of the coal-based direct reduction-magnetic separation method for metallurgical recovery and further purification of metallurgical solid waste. We discuss technological advancements, including rotary kiln, rotary bottom furnace, and tunnel kiln methods, and address environmental and economic aspects, especially in coal-rich regions with limited natural gas resources. Additionally, we have highlighted the technical challenges and developmental bottlenecks of the direct reduction-magnetic separation process; our findings reveal that the improved processes, characterized by high recycling efficiency and low energy consumption and secondary environmental pollution, continue to be the focus of research and development for the sustainable utilization of metallurgical solid waste. [Display omitted] [ABSTRACT FROM AUTHOR]

It is very difficult to extract valuable metals from copper slag and nickel laterite through traditional separation processes due to their complex mineral structure. In this work, a selective co-reduction and magnetic separation process was developed to economically and eco-friendly clean copper slag and synchronously upgrade nickel laterite. Through the innovative process, not only the valuable metals, such as Fe, Ni and Cu, can be recovered, but also the hazardous elements can be removed from copper slag, including As, Pb and Zn. Under optimum conditions, a crud Fe-Ni-Cu alloy assaying 2.51% Ni,1.07%Cu and 87.94% Fe can be manufactured as feed for producing weathering steel, and the corresponding recoveries of Ni, Cu and Fe were 87.15%, 79.68% and 68.96%, respectively. The final tailings containing less toxic elements can be used as raw materials for cement. The mechanism of co-reduction of copper slag and nickel laterite was revealed by XRD, SEM-EDS and EPMA techniques. The results show that a suitable proportion of copper slag and nickel laterite was essential to acquire appropriate amount of liquid phase, thereby improve metallic alloy particles migration and growth, which will significantly increase metal recovery in magnetic separation. The leaching toxicity was used to characterize the environmental impact of tailings obtained by co-reduction and magnetic separation process. [ABSTRACT FROM AUTHOR]

In this study, a new technique was proposed for the economical and environmentally friendly recovery of valuable metals from copper smelting slag while simultaneously upgrading nickel laterite through a co-reduction followed by wet magnetic separation process. Copper slag with a high FeO content can decrease the liquidus temperature of the SiO-AlO-CaO-MgO system and facilitate formation of liquid phase in a co-reduction process with nickel laterite, which is beneficial for metallic particle growth. As a result, the recovery of Ni, Cu, and Fe was notably increased. A crude Fe-Ni-Cu alloy with 2.5% Ni, 1.1% Cu, and 87.9% Fe was produced, which can replace part of scrap steel, electrolytic copper, and nickel as the burden in the production of weathering steel by an electric arc furnace. The study further found that an appropriate proportion of copper slag and nickel laterite in the mixture is essential to enhance the reduction, acquire appropriate amounts of the liquid phase, and improve the growth of the metallic alloy grains. As a result, the liberation of alloy particles in the grinding process was effectively promoted and the metal recovery was increased significantly in the subsequent magnetic separation process. [ABSTRACT FROM AUTHOR]

Copper smelting slag is a useful secondary resource containing high iron and copper, which can be utilized to prepare crude Fe-Cu alloy by a direct reduction-magnetic separation process for making weathering-resistant steel. However, it is difficult to recover iron and copper from the slag by direct reduction since the iron mainly occurs in fayalite and the copper is held in copper sulfide. Therefore, enhancement reduction of copper slag is conducted to improve the recovery of copper and iron. Additives such as NaCO has been proven to be capable of reinforcing the reduction of refractory iron ore. In this research, the effect of NaCO on the carbothermic reduction of copper slag was investigated, and phase transformations during reduction and the distributing characteristics of iron and copper in the alloy and non-metallic phases of the reduced pellets were also studied. The results show that the metallization rate of iron and copper was increased with the addition of NaCO, leading to higher iron and copper recovery in Fe-Cu alloy powder. X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) results confirm that NaCO is capable of enhancing the reduction of fayaltie, copper silicate and copper sulfide, which agrees well with thermodynamic analysis. Furthermore, the reduction mechanism of copper slag was demonstrated based on systematic experimental observations. [ABSTRACT FROM AUTHOR]

During the roasting process, siderite (FeCO3) transforms to magnetite (Fe3O4) along with producing carbon monoxide (CO), but hematite (Fe2O3) needs CO to reduce into magnetite. The process of simultaneously roasting and magnetic separation was developed to treat the low grade siderite and hematite ores without adding any reductant. Effect of mass ratio of S-to-H (siderite ore to hematite ore) on the separation indexes of iron concentrate was discussed. X-ray diffraction was also employed to detect the phase transformations of roasted ores. The technology of simultaneously roasting and magnetic separation is an effective way to treat low grade siderite and hematite ores, and also reduce the emission of CO2because no ruductant is added. [ABSTRACT FROM PUBLISHER]

Siderite is refractory to beneficiate and is directly used as burden for ironmaking because of its high loss of ignition (LOI) and decompositions of carbonate. In this paper, mineralogy of a siderite lump was studied, a process of coal-based direct reduction-magnetic separation of the siderite lump sample was proposed and process parameters have been optimised. It is shown that the final sponge iron powder, assaying 92·40% of Fe and 92·28% of metallisation degree, was manufactured with iron recovery of 96·60% under the following conditions: reducing siderite lump sample with 40·62% Fe and the particle size between 8 and 10 mm at 1050°C for 100 min and carbon to iron ratio of 2·3. Followed by wet grinding of reduced sample to 80% passing 0·037 mm and magnetic separation with Davis tube at 0·1 T magnetic field intensity. The author proposed an effective way of using siderite ores as burdens for electric arc furnace to produce superior special steel. [ABSTRACT FROM AUTHOR]

Recovery of alumina from magnetic separation tailings of red mud has been investigated by NaCO solution leaching. X-ray diffraction (XRD) results show that most of the alumina is present as 12CaO·7AlO and CaO·AlO in the magnetic separation tailings. The shrinking core model was employed to describe the leaching kinetics. The results show that the calculated activation energy of 8.31 kJ/mol is characteristic for an internal diffusion-controlled process. The kinetic equation $$ 1 - \frac{2x}{3} - \left( {1 - x} \right)^{\frac{2}{3}} = \left[ {2.548 \times 10^{ - 2} \times { \exp }\left( {\frac{ - 999.04}{T}} \right)} \right] \times t $$ can be used to describe the leaching process. The effects of NaCO concentration, liquid-to-solid ratio, and particle size on recovery of AlO were examined. [ABSTRACT FROM AUTHOR]

Copper slag, generated mainly during copper smelting, and classified as a potentially harmful waste, is an important secondary resource containing not only valuable metals, such as Cu, Fe, Zn, Co and Ni, in abundant quantities, but also hazardous elements, such as Pb and As. Hence, in response of its potential economic performances and environmental benefits, copper slag needs to be subjected to further metallurgical recycling and cleaning instead of being dumped or abandoned without treatment. Here, a critical review of the generation mechanism, and chemical and physical characteristics of copper slag is provided. Details of the mainstream and recently developed routes for metallurgical recycling and further cleaning of copper slag are also summarised, such as flotation, leaching, and reduction roasting followed by magnetic separation, smelting reduction, and molten modification followed by physical separation. The technical challenges and developmental bottlenecks of the metallurgical processes are pointed out, which indicate that the improved processes characterised by high recycling efficiency, low energy consumption, and low secondary environmental pollution continue to be the focus of research and development in sustainable waste utilization of copper slag. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application. [ABSTRACT FROM AUTHOR]

Attempts to economically and effectively treat copper slag (CS) and ferruginous manganese ore(FMO) using the traditional direct reduction–magnetic separation process have faced many challenges, such as low levels of metal recovery, poor cost-effectiveness and the need for a high proportion of additives. This paper proposes an eco-friendly process to synchronously utilise copper slag and ferruginous manganese ore by co-reduction followed by a magnetic-separation process to solve those problems. In the process, MnO 2 within FMO acted as a catalyst to promote the reduction of fayalite and copper sulphide contained in CS, and thus improve the metallisation rate of Fe and Cu. Meanwhile, CS, possessing the low melting point, can enables more liquid phase generation and improve the growth of alloy particle, which is beneficial for the full liberation of Fe–Cu alloy. Under the optimum conditions, A crude Fe–Cu alloy powder containing 88.83% Fe and 1.07% Cu was prepared, which can be used in an electronic furnace to produce Cu-bearing steels. A high recovery of 85.89% Fe and 87.74% Cu can be obtained using this process, thereby confirming its efficiency. Additionally, Mn contained in the ferromanganese ore was enriched into the magnetic tailing in the form of low-valence manganese (II) oxides, which can be easily extracted by acid leaching. Moreover, the mechanism involved in the co-reduction of CS and FMO was investigated by XRD, SHTT and SEM-EDS techniques, which further confirmed the complementary advantages about an organic integration of CS and FMO can realise the efficient beneficiation of the valuable metals from them. Image 1070 • Iron and copper within CS and FMO were beneficiated efficiently by the new process. • The MnO 2 in FMO was employed as a catalyst to promote reduction of fayalite and copper sulfide in CS. • Synergistic reaction mechanism of CS and FMO in reduction process was revealed. [ABSTRACT FROM AUTHOR]

Abstract An innovative technology for direct reduction-magnetic separation with the addition of Na 2 CO 3 and CaO was studied to upgrade copper slag assaying 40.33% Fe total and 0.65% Cu. It is difficult to recover iron and copper from the slag by direct reduction since the iron mainly occurs in fayalite and the copper exists in copper sulfide. Additives such as Na 2 CO 3 and CaO has been proven to be capable of reinforcing the reduction of refractory iron ore in many papers. In this study, the effect of Na 2 CO 3 dosage and binary basicity (CaO/SiO 2) on the coal-based reduction of copper slag was investigated. The results show that the addition of CaO at 0.5 basicity and 8% sodium carbonate, the recovery of the iron and copper can be significantly improved to 94.3% and 86.5%, respectively. Meanwhile, the iron and copper content of magnetic concentrate are maintained at 90.5% and 1.2%, respectively, which can be used as burden for smelting of weathering steel, and the nonmagnetic tailings obtained in this process can be applied as raw materials in cement and industry, and the dust collected from the direct reduction process contains 50.65% Zn and 8.56% Pb at a recovery of 99.16% and 91.89%, and can be used as feed for extraction of Zn and Pb. Graphical abstract Unlabelled Image Highlights • Direct reduction-magnetic separation process was proposed to treat copper slag. • Thermodynamic analysis of the reduction process was studied. • The mechanism of Na 2 CO 3 in the reduction of the copper slag will be demonstrated. • The effect of CaO in the reduction of the copper slag will be investigated. [ABSTRACT FROM AUTHOR]