Journal of Sustainable Metallurgy最新文献

An efficient and environmentally friendly recovery of platinum group metals (PGMs) from secondary sources is necessary to ensure a sustainable supply of PGMs. In this study, contact with FeCl₂ vapor in the presence of metallic Fe was investigated as a useful pretreatment for leaching PGMs from spent automobile catalysts. Fe-PGM alloys were efficiently formed when Pt, Pd, and Rh wires and Rh₂O₃ powder were subjected to FeCl₂ vapor treatment at 1050 K (777 °C) for approximately 40 min. Further, the leachability of the PGMs in spent automobile catalyst samples increased after a similar vapor treatment was applied. When the pulverized spent catalyst sample without pretreatment was leached with aqua regia at 333 K (60 °C) for 60 min, 88% of Pt, 91% of Pd, and 37% of Rh were extracted. Meanwhile, after vapor treatment at 1050 K, 98% of Pt, 97% of Pd, and 87% of Rh were extracted under the same leaching conditions. Thus, the pretreatment with FeCl₂ vapor, followed by leaching, is a feasible and effective technique for recovering PGMs from spent catalysts.

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The existing pretreatment method for recycling spent lithium iron phosphate (LFP) batteries effectively separates most of the copper foil. However, a small amount of fine copper particles (CP) remains in the LFP battery waste, which is mainly composed of graphite and LFP, affecting the subsequent smelting. Centrifugal gravity concentration (CGC) is a physical separation method that is highly efficient and environmentally friendly and is often used for the separation of fine-grain materials. In this study, it was used for the deep removal of CP from LFP battery waste. The dynamics analysis of the particles in the CGC indicated that CP can be effectively separated from graphite and LFP. The effects of fluidizing water pressure (FWP), relative centrifugal force (RCF), pulp density, and feeding rate on Cu grade, Cu recovery, and Cu separation efficiency (SE) were investigated by single-parameter experiments and response surface methodology (RSM) in CGC. The findings indicate a substantial impact of FWP and RCF on copper recovery, contrasting with the limited influence observed for pulp density and feeding rate on the recovery of Cu. The predicted outcomes from the RSM for Cu grade, Cu recovery, and Cu selectivity (Cu SE) were 85.1993%, 70.0271%, and 67.4004, respectively, under the conditions of FWP at 39.2697 kPa and RCF at 91.9 G. By means of both theoretical analysis and experimental validation, a novel and environmentally sustainable process for the recovery of CP from waste LFP batteries has been proposed.

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A technological process for the deep removal of fine copper particles from lithium iron phosphate battery waste using centrifugal gravity concentration.

Spent lead paste (SLP) obtained from end-of-life lead-acid batteries is regarded as an essential secondary lead resource. Recycling lead from spent lead-acid batteries has been demonstrated to be of paramount significance for both economic expansion and environmental preservation. Pyrometallurgical and hydrometallurgical approaches are proposed to recover metallic lead or lead oxide from SLP. However, traditional pyrometallurgical techniques are plagued by high energy consumption and substantial environmental pollution, whereas hydrometallurgical processes suffer from excessive reagent consumption and wastewater emissions. Benefiting from the technical advantages, electrochemical techniques in the recycling of SLP have attracted extensive interest in the last few years. This review provides a comprehensive summary of electrochemical approaches, technical feasibility, and improvements in recycling SLP. These methods mainly consist of leaching-electrowinning, direct solid-phase electrolysis, suspension electrolysis, electrolysis in ionic liquids, and electrolysis in molten salt. The recent research advances in electrochemical recycling of SLP are discussed. The present state-of-the art challenges and issues including energy consumption and impurity behavior in electrochemical treating SLP are also addressed.

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For carbon neutrality, the use of sinter should be decreased owing to higher CO₂ emission in the sintering process of the blast furnace operations. This trend might contribute to the increased use of iron ore pellets with lower CO₂ emission in the fabrication process, high reducibility and gas permeability due to higher mechanical strength. The pelletizing process mostly uses high-grade iron ore such as magnetite (Fe₃O₄) as the main raw material, which has been depleted due to the increasing demand for pellet production. The current study attempted to replace magnetite ore with low-grade limonite ore (Fe₂O₃∙nH₂O) at different additional levels (10, 30, 50 and 100 wt%). The augmented limonite content influenced the increase in the porosity of pellets, which resulted from dehydration. The effect of microstructure on the compressive strength of mixed pellets before reduction and the reduction behavior of mixed pellets in a hydrogen atmosphere could be elucidated by porosity and pore size distribution analysis. The integration of limonite with magnetite facilitated the formation of small-sized pores, which in turn resulted in a significantly enhanced microstructure, with the limonite-mixed pellets demonstrating compressive strength comparable to that of magnetite pellets. The goethite phase provided a pathway for hydrogen permeability, and consequently, the reduction degree of limonite-mixed pellets in a H₂ atmosphere amounted to a reduction degree of 80%, which is similar to that of magnetite pellets. The mechanical strength of mixed pellets during reduction suggests their potential to withstand the stack layer in blast furnace operations. These findings could suggest the potential to utilize low-grade iron ore pellet process.

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Enhancing blast furnace sustainability via pellet feed optimization

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With the growing concern of environmental protection and waste recycling, recovery of high-value metal from coal fly ash (CFA) has attracted a lot of attention around the world. In our previous study, CaO was employed as an additive to react with mullite (3Al₂O₃·2SiO₂) in CFA to produce CaO·xAl₂O₃, by which the extraction of alumina was strengthened tremendously. However, the dissolving mechanism of CaO·xAl₂O₃ in alkali liquor has not yet been conducted in in-depth research, which casts a shadow for the further progress of the process. In this paper, with the aim of clarifying the alkali dissolving mechanism as well as developing an eco-friendly alumina recovery process, the effect of CaO addition on the mineralogical transformation of CFA and the dissolving behaviors of CaO·xAl₂O₃ in alkali liquor were investigated thoroughly. The results show that the mullite in CFA can be converted to Fe-Si alloys and CaO·xAl₂O₃ with the addition of CaO. Additionally, it is proved that the liquid/solid ratio, the alkali concentration, and the dissolving temperature would be the most critical impactors to decide the extraction rate of alumina. Under the optimal conditions, the extraction rate of alumina attained 93.8% and the CaO can be recycled for cyclic utilization in this process.

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This study investigates the use of graphene oxide (GO) as a nanocollector to remove Zn ions from synthetic wastewater via ion flotation. The effect of various parameters, such as pH, GO concentration, air flow rate, impeller speed, and concentration of sodium dodecyl sulfate (SDS) as an auxiliary collector, on the removal of Zn ions was examined. Under optimal conditions (pH 8.5, GO concentration 40 mg/L, SDS concentration 37.5 mg/L, air flow rate 2 L/min, and impeller speed 800 rpm), Zn ion removal and water recovery reached 90% and 36%, respectively. Characterization techniques, including FTIR, SEM–EDX, and WDX, confirmed the successful interaction between GO and Zn ions, leading to the formation of Zn–GO complexes. This research highlights the potential of GO as a promising and efficient nanocollector for the removal of Zn ions from wastewater through ion flotation, contributing to environmental remediation efforts.

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High-alumina iron ore sintering is characterized by poor sinter indices and high carbon emission due to the limited formation amount of liquid phase. In this study, the conventional Ca-bearing flux (i.e., burnt lime) was substituted by a new Ca-bearing flux with low melting point (i.e., prefabricated calcium ferrite) for the improvement of the formation ability of liquid phase during sintering. The substitution of prefabricated calcium ferrite for burnt lime contributed to the reduction of the formation temperature of liquid phase and the improvement of liquid-phase fluidity. At the optimum substitution ratio of 20%, the strength of sinter compacts was improved by 38.38% in the mini-sintering tests due to the more formation of liquid phase, especially SFCA (i.e., Silico-ferrite of calcium and alumina). In addition, the proportion of high-alumina iron ore can be appropriately increased from 10.20% to 25.20% at the substitution ratio of 20% under the premise of the similar strength of sinter compacts. High-alumina iron ore can be effectively utilized during sintering by pre-preparing the low melting-point flux, which will be further proved by the relevant sinter pot tests in our follow-up study.

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Spent cathode carbon (SCC) contains a considerable amount of soluble fluoride, which is classified as a hazardous emission. In this study, SCC is employed to reduce copper slag, facilitating the recovery of valuable metals, such as copper and iron, while simultaneously fixing soluble fluoride. The results reveal the substantial influences of these factors (temperature, reducing time, and CaO addition) on fluoride fixation, while the reduction temperature and time significantly affect copper recovery. The optimal results of model fitting are that the fluorine fixation is 75.6%, and the copper recovery is 97.2%. The actual fluorine fixation obtained is 75.1%, and the copper recovery is 96.2%, closely aligning with the predicted outcomes of the model. The toxic leaching test and SEM‒EDS analysis show that F⁻ is effectively immobilized in the form of stabilized CaF₂, avoiding the potential hazard of fluorine.

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Secondary aluminum dross (SAD) and red mud residues (RMR) are hazardous wastes generated during the production of alumina and aluminum metal processing, containing unstable AlN, fluoride, chlorides, and alkalis. A novel and pragmatic approach was proposed in this study for the synergistic treatment of waste, wherein hazardous substances are modified through the incorporation of SAD, RMR, and silicate tailings (ST) derived from bauxite flotation, ultimately resulting in the production of ceramic sintered bricks. During brickmaking, AlN in SAD was transformed into Al(OH)₃ through an alkali-catalytic process, and fluorides and chlorides in SAD were efficiently modified and solidified into the silicate mineral marialite Na₄[AlSi₃O₈]₃(F,Cl). Abundant alkalis in RMR transformed into the stable mineral feldspar Na_1–xCa_xAl_1+xSi_3–xO₈, which is the main phase of the sintered brick. The optimal conditions for achieving superior performance of sintered bricks included a mass ratio of SAD, RMR, and ST at 3:3:4, sintering temperature of 1120 °C, and a sintering duration of 2 h. The water absorption rate, porosity, volume density, and compressive strength of the sintered brick in the optimum conditions were 13.69, 26.75%, and 83.04 MPa, respectively, conforming to the industry standards for brick performance.

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The hydrogen reduction of Kahnuj ilmenite concentrate (Kerman, Iran) was studied under different process parameters using Response Surface Methodology (RSM). The effect of major influencing parameters on the reductive mass loss of pellets made from ilmenite concentrate was elucidated. The independent variables examined consisted of the reduction temperature range of 850–1050 °C, pre-oxidation temperature range of 800–1000 °C, and gas flow rates of 200–500 mL min⁻¹. It was found that the reduction temperature and pre-oxidation temperature were the most significant factors affecting the mass loss. The optimum mass loss conditions were determined to be a reduction temperature of 1045 °C, pre-oxidation temperature of 860 °C, and hydrogen flow rate of 217 mL min⁻¹. The optimal experimental mass loss of 15.1% was in accordance with the predicted value of 15.3%. The ilmenite phase transformed into metallic iron, rutile, reduced rutile, and M₃O₅ solid solution through the reduction process.

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