Search

Vanadium nitride (VN) serves as a versatile material in various applications such as electrodes, ceramics, catalysts, and alloy components owing to its robust electrical performance, favorable stability, and high hardness. However, conventional VN synthesis methods require long soaking times and high temperatures. This study investigates a method wherein VxCy powder was soaked in an N2 atmosphere for a shorter period of time at a lower temperature to produce high-quality VN particles. The mechanism underlying this process was investigated via thermodynamic analyses, ab initio molecular dynamics (AIMD) simulations, and experimental studies. Thermodynamic analysis validates the thermodynamic feasibility of the reactions between VxCy and N2 to produce VN, while the atomic-level interactions between VxCy, N2, and surplus C atoms were comprehensively elucidated. By analyzing the two systems, it was discovered that the surplus C promoted the combination of N2 molecules with V atoms to form V–N in shorter AIMD simulation durations. Surplus C increased the chance of N2 molecules and V atoms to contact, similar to a catalytic effect, by activating N2 molecules to decompose and further reacted with V atoms to form VN. According to the experimental results, high-quality VN particles were formed at a heating temperature of 1323 K and soaking period of 90 min. Field-emission scanning electron microscopy (SEM) coupled with energy-dispersive spectrometry (EDS), particle size distribution analysis, and X-ray diffraction (XRD) were used to characterize the final product. The O and N contents were measured by an O/N analyzer at 0.11% and 17.4%, respectively. Accordingly, a C/S analyzer measured the C content at 3.92%. These analyses indicate that high-quality VN can be obtained by the VxCy nitridation in N2 atmosphere.

Huge amounts of Au and Ag are recovered from the hazardous waste lead anode slime. The conventional extraction of precious metals from lead anode slime is based on pyrometallurgical and electrolytic processes, which are seriously conditioned by the separation of harmful elements As and Sb. In this paper, an innovative and efficient oxidation–vacuum volatilization–carbon reduction process was proposed to separate and enrich Ag and Au from lead anode slime. Before vacuum volatilization, selective oxidation of the lead anode slime was performed. Then, vacuum volatilization and vacuum carbon reduction were used to obtain a gold- and silver-rich alloy. The feasibility of the process was verified experimentally and theoretically. The effects of temperature and time on vacuum volatilization separation and reduction enrichment were investigated. The experimental results showed that the Ag content in the resulting gold- and silver-rich alloy was as high as 67.58%, Au was as high as 4287 g/t, and the efficiencies for the recovery of Ag and Au from the lead anode slime were 99.25% and 99.91%, respectively. The gold- and silver-rich alloy can be directly used to produce Ag ingots. Moreover, no gas or wastewater was discharged in this process, so Ag and Au were recovered in a sustainable and cleaner manner.

The carbochlorination process of low-grade titanium slag and the formation mechanism of intermediate products are difficult to completely explain at the microscopic level. According to the phase and chemical composition of low-grade titanium slag, MgTi4FeO10 was used to study the carbochlorination mechanism. The effects of the Fe and Mg in the complex oxide on the chlorination rate and the important roles of C were elucidated by ab initio molecular dynamic (AIMD) simulation. The difference in the adsorption behavior of the intermediate product COCl2 on MgTi4FeO10(011) and TiO2(110) was also analyzed. Thermodynamics, AIMD simulation, the adsorption configuration of COCl2 and experimental results indicated that the presence of rutile is the bottleneck restricting the high efficiency chlorination of low-grade titanium slag. This study is expected to provide ideas for the further improvement of the chlorination efficiency and rate of low-grade titanium slag.

Lead anode slime, which is produced by electrolytic refining of refined Pb, is a significant source of the rare metal Te. However, traditional methods for treating lead anode slime are characterized by complex processes, hazardous waste discharge, high energy consumption, repeated reduction and oxidation, and inefficient separation of Te. Therefore, a novel, green, and efficient vacuum gasification process for Te separation and enrichment was developed in this study. The optimal gasification temperature and time of Te volatilization were investigated using two-step, high-temperature and low-temperature vacuum distillation experiments; the system pressure was maintained at 5–15 Pa for both steps. Te (96.07%) in lead anode slime was separated using high-temperature vacuum gasification at 1173 K for 60 min and low-temperature vacuum gasification at 723 K for 45 min, yielding Te-rich volatiles with a 4.80% tellurium content. Te was enriched more than 16 times. Te existed as Te and TeO2 in the tellurium-rich volatiles, making the volatiles an excellent raw material for further tellurium purification. This two-step vacuum gasification process provides theoretical guidance for effective and sustainable recovery of Te from lead anode slime with no waste gas or water, which meets the need for cleaner production methods in the metallurgical industry.

In this study, the phase composition, morphology, and element distribution of Mg impurities in a low-grade titanium slag and in its chlorinated residue after carbochlorination were identified using XRD, SEM-EDS, and MLA. Most Mg impurities existed as anosovite, rutile, titanaugite, and Ti silicate phases before the carbochlorination process. The thermodynamic analysis revealed that the chlorination tendencies of Mg, Ti, Ca, Fe, and Mn oxides in the original titanium slag was much higher than those of Si and Al oxides in the temperature range of 700–850 °C. In addition, the binary phase diagram analysis indicates that the magnesium chloride (MgCl2) byproduct formed Na2MgCl4 eutectic salts in the NaCl-based salt bath. The carbochlorination experiments of the Mg-bearing titanium slag show that the chlorination ratio of magnesium oxide was above 93% under the suitable industrial conditions used for the extraction of titanium from Mg-bearing titanium slag. In addition, the formation of Na2MgCl4 eutectic salts after carbochlorination was confirmed, indicating that the negative effect of MgCl2 on the chlorination process was effectively eliminated. The Mg impurities in the chlorinated residue existed as titanaugite, quartz, chlorite, and rutile phases. Furthermore, we found that the carbochlorination of Mg-bearing titanium slag in chloride media effectively improved the comprehensive utilization efficiency of the Mg-bearing titanium slag. We believe that the proposed carbochlorination mechanism of the Mg-bearing titanium slag will provide thorough understanding and useful guidance on the practical industrial application of Mg-bearing titanium slag.

The use of copper anode slime (CAS) for the removal of lead, bismuth, and arsenic is the key to recovering precious metals. In this paper, vacuum differential gravimetry experiments combined with thermodynamic equilibrium calculations reveal the effects of the temperature, system pressure, and carbon concentration on the interactions among Pb, Bi, and As during reduction. The carbon content is a direct factor limiting the reduction reactions of sulfate and arsenate phases, and affects the presence of arsenate reduction products. When the carbon content of the system is insufficient, As mainly exists as oxides in the reduction products, and the form of arsenic gradually converts to monomers with increasing carbon content. The reduction product Bi2S3 gradually converts to Bi and BiS as the temperature increases. The effect of temperature on arsenate is mainly related to the phase of the Pb- and Bi-containing reduction products. Moreover, vacuum differential gravimetry experiments were performed to verify the phase transformation of As, Pb, and Bi in CAS during vacuum carbon thermal reduction.

With the widespread use of cadmium telluride solar cells, environmental protection, and effective recycling approaches for solar cell component waste have become topics of concern. As an emerging metal smelting technology, vacuum metallurgy technology has broad application prospects in primary metal refining and the recycling of secondary non-ferrous scraps. Thus, this study proposes a new method for the separation and recovery of rare metals from cadmium telluride waste through sulfur smelting and vacuum distillation. In this process, sulfur is smelted with cadmium telluride to produce tellurium with a high vapor pressure. The tellurium was then separated and purified by multi-stage vacuum distillation. The results show that the tellurium purity can reach up to 99.97% and the tellurium recovery rate was above 99%. The cadmium and sulfur contents in the tellurium were 0.0061% and 0.0194%, respectively. Moreover, the cadmium sulfide produced during the smelting process can be enriched by vacuum distillation, resulting in 99.6% purity. This technology strongly aligns with the “reduce, reuse, and recycle” principle for solid waste, and provides a basis for the sustainable development of the photovoltaic industry.

Arsenic–iron precipitate was treated using a carbon thermal magnetization reduction method in order to recover arsenic and iron. Arsenic–iron precipitate mixed with coke powder was roasted at a low temperature; arsenic was recovered in the form of As2O3, and iron was recovered in the form of Fe3O4. The volatilization rate of arsenic was 97.45%, and the content of arsenic in the precipitate was decreased to 0.60%. Iron and arsenic were recovered in the form of Fe3O4 and As2O3 with a purity of 99.91 wt.% under the conditions of a roasting temperature of 650 °C, coke powder addition of 25 wt.%, a roasting time of 180 min, and an argon flow rate of 10 L/min. The volatilization of arsenic was controlled by a chemical controlling step at 20–100 min, and this was switched to a diffusion controlling step at 120–180 min by kinetic experiments. The reaction mechanism of arsenic and iron under carbon thermal magnetization reduction was as follows: in the early stage of the reaction, a large amount of FeAsO4 was decomposed into As2O3 and Fe3O4; in the middle and late stages of the reaction, FeAsO4 was continuously decomposed and reduced, and the content of Fe3O4 was continuously increased until all iron was magnetized to generate Fe3O4, and the decomposed As2O3 volatilized into dust. Arsenic reacted with CaO to generate Ca3(AsO4)2, and this may be the reason why arsenic could not be removed completely.

In the present research, the structural, the relative stable, and the electronic properties of AlnLin (n = 2 – 12) clusters were investigated by density functional theory (DFT). By comparing the calculated values of Al2 and Li2 dimers with experimental ones, the reliability of the proposed method was proved. Furthermore, by considering the values of average binding energy (Eb), vertical ionization potential (VIP), vertical electron affinity (VEA), fragmentation energy (△E), second-order energy difference (△2E), HOMO-LUMO (HL) gap, and chemical hardness (η) were calculated. It was found Fragmentation energy, second-order energy difference, VIP, VEA, the chemical stability and HOMO-LUMO gap exhibit odd-even oscillatory behaviours along with cluster size and have extreme values at n = 5 revealed Al5Li5 cluster yielded excellent stability. Those can be well explained by the density of states (DOS) that Li and Al atoms with stronger covalent bonds. Therefore, Al5Li5 cluster can be used as an ideal candidate for calculating Wilson parameters of Al-Li alloys.

Tellurium is the indispensable base material of semiconductors in solar panels. Traditional tellurium recycling, a highly complicated separation process, has exhausted reagents and energy sources whilst producing waste residue and water containing multitudinous heavy metal that is hugely harmful to the ecological environment. A clean and eco-friendly vacuum distillation-directional condensation treatment was investigated for its potential to recycle tellurium from tellurium-rich lead anode slime (TLAS). The optimal distillation temperature and response time conditions of 1173 K and 50 min were obtained based on a large number of experiments. Gasification results indicated that under the optimal conditions of distillation temperature 1173 K, constant temperature time 50 min, and system pressure 5–15 Pa, 92% of tellurium was volatilized and enriched into the condenser from TLAS. Condensate results revealed that 88% of elemental tellurium was directly recovered in the volatile matter. The appropriate gasification-condensation processes realized a clean utilization to extract tellurium and separate multi valuable metals effectively.

In this study, we investigated the preparation process of lithium metal using a novel carbothermic reduction process. Herein, thermodynamic calculations and experimental research methods were used to investigate the novel carbothermal reduction process of LiAlO _2 for preparing lithium metal in a vacuum. The results suggest that the temperature of the chemical reaction can be significantly reduced by reducing the pressure in the system. When the system pressure was 10 Pa, the reduction temperature, reduction time, molar ratio of C/LiAlO _2 , and reduction rate were 1623 K, 120 min, 0.9, and 79.01%, respectively. Furthermore, the lithium content in the reduction residue was 2.1 wt%, suggesting the presence of the LiAl _5 O _8 phase. Under these conditions, when 20% CaO was added, the reduction rate of lithium increased to 99.38%, and the lithium in the reduction residue takes the form of CaAl _2 O _4 . This shows that CaO, as an additive, can promote reduction, compromise the effect of LiAl _5 O _8 , and increase the reduction rate of lithium.