Editorial

5 pages, 200 KiB

Open AccessEditorial

Separation Techniques for the Efficient and Green Recovery of Metal Minerals

by Hongtao Chang and Guoquan Zhang

Separations 2023, 10(10), 520; https://doi.org/10.3390/separations10100520 - 25 Sep 2023

Cited by 1 | Viewed by 1163

In 2022~2023, eight high-quality papers were published in the Special Issue of Separations entitled “Efficient and Green Recovery of Metal Minerals” [...] Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

Research

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13 pages, 2568 KiB

Open AccessArticle

Basic Research on Selective Extraction of Iron from Titanium Dioxide Waste Acid to Prepare Iron Phosphate Precursors

by Xuejiao Cao, Yang Chen, Xinxing Liang, Yibing Li, Weiguang Zhang, Zhenlei Cai and Ting’an Zhang

Separations 2023, 10(7), 400; https://doi.org/10.3390/separations10070400 - 11 Jul 2023

Cited by 2 | Viewed by 1181

Abstract

In view of the current situation wherein acid resources and valuable components in titanium dioxide waste acid cannot be effectively extracted and are prone to secondary pollution, our research team proposed a new technique consisting of step extraction and the comprehensive utilization of [...] Read more.

In view of the current situation wherein acid resources and valuable components in titanium dioxide waste acid cannot be effectively extracted and are prone to secondary pollution, our research team proposed a new technique consisting of step extraction and the comprehensive utilization of titanium dioxide waste acid. In this paper, the thermodynamics of selective precipitation and the preparation of doped iron phosphate from waste acid were studied. The thermodynamics results show that the content of Al³⁺, Mn²⁺, Mg²⁺, and Ca²⁺ in the reaction system can be tuned by adjusting the pH during the pre-precipitation process. In the first step, these impurity ions should be settled as much as possible; then, Fe²⁺ should be oxidized to Fe³⁺ so as to obtain iron phosphate with higher purity in the next step of the precipitation process. The effects of the reaction temperature, seed crystals, pH value, and P/M on the precipitation process were investigated in detail. The experimental results show that in the reduced state, the optimal precipitation conditions are a temperature of 75 °C, an initial pH value of 4.5, and an optimal P/M molar ratio of 1.1. In the oxidized state, the optimal precipitation conditions are a temperature of 60 °C, a solution pH = 2.5, and a reaction time of 25 min. After calcination, the precipitate mainly consists of iron phosphate, which basically meets the requirements of an iron phosphate precursor. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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11 pages, 3309 KiB

Open AccessArticle

Exploration of Large-Scale Application of Efficient and Clean Utilization of Low-Grade Bauxite

by Yang Chen, Fei Long, Xuejiao Cao, Yibing Li, Weiguang Zhang, Tingan Zhang and Guozhi Lv

Separations 2023, 10(6), 336; https://doi.org/10.3390/separations10060336 - 30 May 2023

Cited by 1 | Viewed by 1164

Abstract

In recent years, the rapid development of the domestic alumina industry has greatly accelerated the consumption of high-alumina–silica-ratio bauxite resources in China. The development of an efficient and clean utilization technology applicable to low-grade bauxite in China is not only a requirement for [...] Read more.

In recent years, the rapid development of the domestic alumina industry has greatly accelerated the consumption of high-alumina–silica-ratio bauxite resources in China. The development of an efficient and clean utilization technology applicable to low-grade bauxite in China is not only a requirement for resource and environmental protection, but also a powerful guarantee to maintain the sustainable development of China’s aluminum industry. Based on this, the authors’ team proposed a new process for the treatment of low-grade bauxite ore via a calcification–carbonization method from the perspective of equilibrium solid-phase reconstruction and achieved the first industrial-scale trial run on the basis of existing laboratory research. The results show that the mass fraction of Na₂O in bauxite residue can be reduced to 0.95% in the treatment of typical diaspore bauxite, the A/S in the bauxite residue can be reduced to 0.85 after two-time carbonization–alumina dissolution, and the actual alumina dissolution rate can reach 81.32%. The relevant results verified the feasibility and advantages of the calcification–carbonization method in industrial production. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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11 pages, 1603 KiB

Open AccessArticle

Degradation of Azo Dye by Ultrasound in Rotating Flow Field

by Chunwei Shi, Fan Yang and Xiaogang Qu

Separations 2023, 10(5), 321; https://doi.org/10.3390/separations10050321 - 22 May 2023

Cited by 1 | Viewed by 916

Abstract

Azo dyes such as Congo red can easily cause cancer when they come into contact or are absorbed by the human body, so it is urgent to find a fast and simple method for degrading Congo red. In order to better achieve this [...] Read more.

Azo dyes such as Congo red can easily cause cancer when they come into contact or are absorbed by the human body, so it is urgent to find a fast and simple method for degrading Congo red. In order to better achieve this research goal, an ultrasonic method was used to degrade Congo red solution in a rotating flow field. The concentration of hydroxyl radical in the solution was significantly increased under the action of ultrasonic cavitation, chemical action of zero valent iron, and mechanochemistry. Under the strong oxidation of hydroxyl radical and the reduction of nano zero valent iron peeled off in the reaction process, the reaction speed is significantly accelerated and should promote the reaction. The effect of increasing stirring and adding iron powder particles on ultrasonic cavitation was studied by numerical simulation, and the yield of hydroxyl radical in the system was measured by fluorescence analysis. The experimental results show that, first, the rotating field formed by mixing increases the uniformity of ultrasonic sound field distribution and the amplitude of sound pressure, and it improves the cavitation intensity. In the effective dispersion area, the strong ultrasonic wave can form a temporary high-energy microenvironment in the suspension through cavitation, generate high strength shockwaves and micro jets, and thus significantly deagglomerate the iron powder aggregates. The addition of iron powder particles then provides a complementary Fenton reagent for the degradation reaction. The concentration of hydroxyl radicals in the solution was significantly increased by the synergy of the two actions. The degradation rate of Congo red reached more than 99% after 30 min of reaction. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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16 pages, 6957 KiB

Open AccessArticle

High Value-Added Utilization of Waste Hydrodesulfurization Catalysts: Low-Cost Synthesis of Cathode Materials for Lithium-Ion Batteries

by Junbo Zhou, Lang Qiu, Yao Li, Yuting Deng, Qing Zhao, Yang Hu, Fuqiren Guo, Chaoqiong Zhu, Benhe Zhong, Yang Song and Xiaodong Guo

Separations 2022, 9(12), 449; https://doi.org/10.3390/separations9120449 - 19 Dec 2022

Cited by 2 | Viewed by 1618

Abstract

This work introduces a one-step method for the preparation of layered oxide cathode materials utilizing pure Ni and Co mixed solution obtained from the waste hydrodesulfurization (HDS) catalyst. An efficient non-separation strategy with pyrometallurgical-hydrometallurgical (pyro-hydrometallurgical) process consisting of roasting and leaching is proposed. [...] Read more.

This work introduces a one-step method for the preparation of layered oxide cathode materials utilizing pure Ni and Co mixed solution obtained from the waste hydrodesulfurization (HDS) catalyst. An efficient non-separation strategy with pyrometallurgical-hydrometallurgical (pyro-hydrometallurgical) process consisting of roasting and leaching is proposed. Most of the impurity metal elements such as Mo and V were removed by simple water leaching after the waste HDS catalyst was roasted with Na₂CO₃ at 650 °C for 2.5 h. Additionally, 93.9% Ni and 100.0% Co were recovered by H₂SO₄ leaching at 90 °C for 2.5 h. Then, LiNi_0.533Co_0.193Mn_0.260V_0.003Fe_0.007Al_0.004O₂ (C–NCM) was successfully synthesized by hydroxide co-precipitation and high temperature solid phase methods using the above Ni and Co mixed solution. The final C–NCM material exhibits excellent electrochemical performance with a discharge specific capacity of 199.1 mAh g⁻¹ at 0.1 C and a cycle retention rate of 79.7% after 200 cycles at 1 C. This novel process for the synthesis of cathode material can significantly improve production efficiency and realize the high added-value utilization of metal resources in a waste catalyst. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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11 pages, 1702 KiB

Open AccessArticle

Recovery of Valuable Metals from Cathode—Anode Mixed Materials of Spent Lithium-Ion Batteries Using Organic Acids

by Kun Wang, Guoquan Zhang and Mingzhi Luo

Separations 2022, 9(9), 259; https://doi.org/10.3390/separations9090259 - 13 Sep 2022

Cited by 3 | Viewed by 1779

Abstract

Spent lithium-ion batteries (LIBs) contain a large number of valuable metals and will be an important strategic resource in the future. Therefore, recycling is extremely important. In this work, acetic acid and hydrogen peroxide were used as leaching agents to recover valuable metals [...] Read more.

Spent lithium-ion batteries (LIBs) contain a large number of valuable metals and will be an important strategic resource in the future. Therefore, recycling is extremely important. In this work, acetic acid and hydrogen peroxide were used as leaching agents to recover valuable metals (lithium, cobalt, nickel, manganese, and aluminum) from cathode and anode materials (LiCoO₂, LiAl_0.2Co_0.8O₂, and C) of spent LIBs. The leaching solution and leaching residue were analyzed by inductive plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The optimum experimental conditions were obtained by changing the concentration of acetic acid, solid–liquid ratio, reaction temperature, time, and the concentration of hydrogen peroxide reducing agent. Under the experimental conditions of 2 M acetic acid, 4.0 vol.% H₂O₂, 20 g/L, and 70 °C for 40 min, the leaching rates of lithium, cobalt, nickel, manganese, and aluminum reached 98.56%, 94.61%, 96.39%, 97.97%, and 94.7%, respectively. This hydrometallurgical process is simple and environmentally friendly and maximizes the recovery of valuable metals from spent LIBs. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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14 pages, 2796 KiB

Open AccessArticle

Recovery of Rare Metals from Superalloy Scraps by an Ultrasonic Leaching Method with a Two-Stage Separation Process

by Long Wang, Sujun Lu, Jiayuan Fan, Yutian Ma, Juan Zhang, Shiyang Wang, Xiaoyao Pei, Yuan Sun, Guozhi Lv and Tingan Zhang

Separations 2022, 9(7), 184; https://doi.org/10.3390/separations9070184 - 20 Jul 2022

Cited by 1 | Viewed by 1362

Abstract

Superalloy scraps are deemed as potential unconventional sources of rare metals. In this study, an ultrasonic leaching method with a two-stage separation process was proposed. A series of Eh-pH diagrams for rare metals was constructed, and the results indicated that the leaching and [...] Read more.

Superalloy scraps are deemed as potential unconventional sources of rare metals. In this study, an ultrasonic leaching method with a two-stage separation process was proposed. A series of Eh-pH diagrams for rare metals was constructed, and the results indicated that the leaching and separation process could be realized by adjusting the potential and pH values of leaching solutions. In the ultrasonic leaching process, results showed that the economic leaching percentages of Re, Ni, Co, Al, and Cr were 92.3%, 95.2%, 98.5%, 98.7%, and 97.5%, respectively. Compared with conventional leaching, ultrasonic leaching can improve the leaching percentages of rare metals by approximately 20%. In the two-stage separation process, the optimal recovery efficiencies of Al and Cr were 94.6% and 82.1% at a pH of 4.5, and Ni and Co were 99.5% and 98.3% at a pH of 7.5. With a two-stage precipitate process, rare metals can be efficiently recovered without generating any waste acid. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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Review

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14 pages, 4197 KiB

Open AccessReview

Application of Nanofiltration Membrane Based on Metal-Organic Frameworks (MOFs) in the Separation of Magnesium and Lithium from Salt Lakes

by Yueyu Liu, Rong Zhu, Chandrasekar Srinivasakannan, Tingting Li, Shiwei Li, Shaohua Yin and Libo Zhang

Separations 2022, 9(11), 344; https://doi.org/10.3390/separations9110344 - 03 Nov 2022

Cited by 8 | Viewed by 2909

Abstract

With the increasing demand for lithium, the shortage of resources has become increasingly apparent. In order to conserve resources and to improve recovery, the extraction of lithium from salt lakes has become mandatory for sustainable development. Porous metal-organic framework (MOF) materials have attracted [...] Read more.

With the increasing demand for lithium, the shortage of resources has become increasingly apparent. In order to conserve resources and to improve recovery, the extraction of lithium from salt lakes has become mandatory for sustainable development. Porous metal-organic framework (MOF) materials have attracted extensive attention due to their high/tunable porosity, pore function, multiple pore structures/compositions, and open metal sites. Moreover, MOFs combine the advantages of other porous materials and have a wide range of applications, which have received significant interest from the scientific community. Therefore, the selection of MOFs materials, the optimization of preparation methods, and the research of lithium separators are key directions to improve the total yield of lithium resources in salt lakes in China. This study aims to improve the comprehensive utilization of resources after lithium extraction and strengthen the engineering technology research of lithium extraction from salt lakes. This study can help to achieve the goal of efficient, integrated, and sustainable utilization of salt lake resources. An attempt has been made to summarize the types and preparation methods of MOFs materials, as well as the separation mechanism of MOFs nanofiltration membranes, with reference to its application in lithium extraction from salt lake brine. Finally, the future development of MOFs nanofiltration membranes for lithium extraction from salt lakes is also proposed. Full article

(This article belongs to the Special Issue Efficient and Green Recovery of Metal Minerals)

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