High-Performance Recovery of Vanadium(V) in Leaching/Aqueous Solution by a Reusable Reagent-Primary Amine N1519

Efficient extraction and stripping for recovering vanadium­(V) from the leaching/aqueous solution of chromium-bearing vanadium slag (V–Cr slag) are essential to the reuse of heavy metals. The performance characteristics of a new reagent, primary amine N1519, were first reported for extracting vanadium. With a phase ratio of organic to aqueous up to 1:1, 99.7% of vanadium­(V) can be effectively extracted from the leaching/aqueous solution, and powder of NH₄VO₃ was obtained through the stripping with ammonia. The new reagent can be recyclable in use for sustainable reuse after stripping. Different extraction conditions, e.g., the initial pH of the leaching/aqueous solution and the molar quantity of N1519 were investigated. The powder of vanadium-organic compounds (VOC) with N1519 formed in the process of extraction was obtained and purified through three-steps of solvent-out crystallizations. The hydrogen bond association mechanism of extraction was illustrated with the structure of VOC and the enthalpy change in extraction process. The fast extraction process and slow stripping procedure for recovering vanadium­(V) are suitable for use in annular centrifugal contactors with very short contact/resident times and mixed-settler extractors with very good mass transfer, respectively. The results offer significant advantages over conventional processes

Sustainable Preparation of LiNi_1/3Co_1/3Mn_1/3O₂–V₂O₅ Cathode Materials by Recycling Waste Materials of Spent Lithium-Ion Battery and Vanadium-Bearing Slag

Waste streams containing heavy metals are always of concern from both environmental and resource-depleting points of view. The challenges are in most cases related to the effectiveness for high-value-added materials recovery from such waste, with which the environmental impacts during recycling shall be low. In this research, two typical heavy-metal-containing waste streams, i.e., spent lithium-ion batteries and vanadium-bearing slag, were simultaneously treated, and this enables regeneration of the LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials which was considered difficult because of the dislocation of nickel and lithium ions during electrochemical performance. By using the intermediate product during vanadium-bearing slag treatment, the vanadium-embedded cathode material can be prepared which delivers excellent electrochemical performances with a specific capacity of 156.3 mA h g^–1 after 100 cycles at 0.1C with the capacity retention of 90.6%; even the additive amount is only 5%. A thin layer of vanadium oxide is found to be effective to promote electrochemical performance of the cathode material. Using the principles of green chemistry, this process enables high-performance cathode material regeneration without introducing extraction chemicals and with much lower environmental impacts as compared to traditional metallurgical technologies

Optimal Design of Solvent Blend and Its Application in Coking Wastewater Treatment Process

One of the key steps of coking wastewater treatment is phenolic and tar removal via extraction. However, the high loss of the extractant, i.e., methyl isobutyl ketone (MIBK), leads to the high cost of the process. The adoption of a novel solvent or solvent blend is considered as an efficient way to address this problem. In this paper, seven solvents (benzene, toluene, m-xylene, ethylbenzene, 1, 3, 5-trimethylbenze, cyclohexane, and octanol), selected as candidate diluters for MIBK according to operating requirements, are studied with a nonlinear programming (NLP) model based on ideal counter-current extraction. The results, verified with experiments, suggest toluene is the most promising candidate. Further investigation of this solvent blend reveals that both <i>D</i>_blend (the distribution coefficient of phenol between solvent blend and water) and <i>m</i>_MIBK (the MIBK concentration in raffinate) increase with <i>x</i>_MIBK (the molar fraction of MIBK in blend). The trade-off between the extraction performance and MIBK loss recommends the blend with <i>x</i>_MIBK = 0.05 as extractant for coking wastewater treatment. An industrial process consisting of extraction, back stripping, distillation, and mixer is presented. A corresponding NLP model is established for its operating optimization. To improve the accuracy, the representatives of typical phenolics and tar in wastewater (2,4 dimethyl phenol, m-xylene, and quinolone) are also considered in addition to phenol. The case study indicates that the blend exhibits economic advantage over pure MIBK with a makeup cost of 11.15 ¥/t, much less than the 185.15 ¥/t in the case of MIBK

A Closed-Loop Process for Selective Metal Recovery from Spent Lithium Iron Phosphate Batteries through Mechanochemical Activation

With the increasing consumption of lithium ion batteries (LIBs) in electric and electronic products, the recycling of spent LIBs has drawn significant attention due to their high potential of environmental impacts and waste of valuable resources. Among different types of spent LIBs, the difficulties for recycling spent LiFePO₄ batteries rest on their relatively low extraction efficiency and recycling selectivity in which secondary waste is frequently generated. In this research, mechanochemical activation was developed to selectively recycle Fe and Li from cathode scrap of spent LiFePO₄ batteries. By mechanochemical activation pretreatment and the diluted H₃PO₄ leaching solution, the leaching efficiency of Fe and Li can be significantly improved to be 97.67% and 94.29%, respectively. To understand the Fe and Li extraction process and the mechanochemical activation mechanisms, the effects of various parameters during Fe and Li recovery were comprehensively investigated, including activation time, cathode powder to additive mass ratio, acid concentration, the liquid-to-solid ratio, and leaching time. Subsequently, the metal ions after leaching can be recovered by selective precipitation. In the whole process, about 93.05% Fe and 82.55% Li could be recovered as FePO₄·2H₂O and Li₃PO₄, achieving selective recycling of metals for efficient use of resources from spent lithium ion batteries