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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.

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.

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.