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Foquan Gu
School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China

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Review
Published: 24 June 2020 in Metals
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NdFeB permanent magnet scrap is regarded as an important secondary resource which contains rare earth elements (REEs) such as Nd, Pr and Dy. Recovering these valuable REEs from the NdFeB permanent magnet scrap not only increases economic potential, but it also helps to reduce problems relating to disposal and the environment. Hydrometallurgical routes are considered to be the primary choice for recovering the REEs because of higher REEs recovery and its application to all types of magnet compositions. In this paper, the authors firstly reviewed the chemical and physical properties of NdFeB permanent magnet scrap, and then carried out an in-depth discussion on a variety of hydrometallurgical processes for recovering REEs from the NdFeB permanent magnet scrap. The methods mainly included selective leaching or complete leaching processes followed by precipitation, solvent extraction or ionic liquids extraction processes. Particular attention is devoted to the specific technical challenge that emerges in the hydrometallurgical recovery of REEs from NdFeB permanent magnet scrap and to the corresponding potential measures for improving REEs recovery by promoting the processing efficiency. This summarized review will be useful for researchers who are developing processes for recovering REEs from NdFeB permanent magnet scrap.

ACS Style

Yuanbo Zhang; Foquan Gu; Zijian Su; Shuo Liu; Corby Anderson; Tao Jiang. Hydrometallurgical Recovery of Rare Earth Elements from NdFeB Permanent Magnet Scrap: A Review. Metals 2020, 10, 841 .

AMA Style

Yuanbo Zhang, Foquan Gu, Zijian Su, Shuo Liu, Corby Anderson, Tao Jiang. Hydrometallurgical Recovery of Rare Earth Elements from NdFeB Permanent Magnet Scrap: A Review. Metals. 2020; 10 (6):841.

Chicago/Turabian Style

Yuanbo Zhang; Foquan Gu; Zijian Su; Shuo Liu; Corby Anderson; Tao Jiang. 2020. "Hydrometallurgical Recovery of Rare Earth Elements from NdFeB Permanent Magnet Scrap: A Review." Metals 10, no. 6: 841.

Journal article
Published: 02 June 2020 in Powder Technology
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A novel strategy for selective recovery of chromium from ferronickel slag via microwave assisted sodium peroxide roasting followed by water leaching was proposed in this study. The experimental results showed that 94.21% of chromium was leached with 64.43% of sodium and 6.13% of silicon, while only 0.06 wt% chromium remained in the leaching residue when the mixture of ferronickel slag and sodium peroxide with the mass ratio of 1 was roasted at 600 °C for 20 min before leaching at 50 °C for 1 h with the liquid-to-solid ratio of 10 mL/g. In comparison with conventional roasting, the microwave roasting showed a much higher efficiency for recovering chromium from ferronickel slag with the recovery of chromium increased by 12.92%, resulting from the enhanced conversion of Cr2O3 in the slag to NaCrO2 and from the looser and more porous structure during the roasting process which was beneficial for subsequent water leaching.

ACS Style

Zhiwei Peng; Liancheng Wang; Foquan Gu; Huimin Tang; Mingjun Rao; Yuanbo Zhang; Guanghui Li; Tao Jiang. Recovery of chromium from ferronickel slag: A comparison of microwave roasting and conventional roasting strategies. Powder Technology 2020, 372, 578 -584.

AMA Style

Zhiwei Peng, Liancheng Wang, Foquan Gu, Huimin Tang, Mingjun Rao, Yuanbo Zhang, Guanghui Li, Tao Jiang. Recovery of chromium from ferronickel slag: A comparison of microwave roasting and conventional roasting strategies. Powder Technology. 2020; 372 ():578-584.

Chicago/Turabian Style

Zhiwei Peng; Liancheng Wang; Foquan Gu; Huimin Tang; Mingjun Rao; Yuanbo Zhang; Guanghui Li; Tao Jiang. 2020. "Recovery of chromium from ferronickel slag: A comparison of microwave roasting and conventional roasting strategies." Powder Technology 372, no. : 578-584.

Article
Published: 27 January 2020 in International Journal of Applied Ceramic Technology
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The study provides a method for improving the quality of the refractory material prepared from ferronickel slag by promoting the spinel formation and growth in the slag which was sintered with sintered magnesia and chromium oxide in a broad sintering temperature range from 1200 °C to 1500 °C. According to the thermodynamic analysis, except for forsterite due to the addition of sintered magnesia, a number of high‐melting‐point spinel phases can also be formed in the presence of chromium oxide and this trend becomes more apparent with increasing sintering temperature, along with declined presence of low melting point clinopyroxene, mainly enstatite. This expectation was verified by conversion of a part of original phase of ferronickel slag, olivine, to two main spinel phases, including magnesium aluminate spinel and donathite which was produced by the replacement of nontoxic Cr3+ ions with Fe3+ ions in the octahedral vacancies of magnesium chromate spinel. The formation and growth of these spinel phases were promoted by elevating temperature from 1200 °C to 1500 °C, which accelerated the transition of initially generated enstatite to a glassy phase, in favor of densification. The formation and growth of spinel during sintering, contributing to high refractoriness and compressive strength of the resulting refractory materials.

ACS Style

Foquan Gu; Zhiwei Peng; Yuanbo Zhang; Huimin Tang; Weiguang Tian; JoonHo Lee; Mingjun Rao; Guanghui Li; Tao Jiang. Promoting spinel formation and growth for preparation of refractory materials from ferronickel slag. International Journal of Applied Ceramic Technology 2020, 17, 1701 -1712.

AMA Style

Foquan Gu, Zhiwei Peng, Yuanbo Zhang, Huimin Tang, Weiguang Tian, JoonHo Lee, Mingjun Rao, Guanghui Li, Tao Jiang. Promoting spinel formation and growth for preparation of refractory materials from ferronickel slag. International Journal of Applied Ceramic Technology. 2020; 17 (4):1701-1712.

Chicago/Turabian Style

Foquan Gu; Zhiwei Peng; Yuanbo Zhang; Huimin Tang; Weiguang Tian; JoonHo Lee; Mingjun Rao; Guanghui Li; Tao Jiang. 2020. "Promoting spinel formation and growth for preparation of refractory materials from ferronickel slag." International Journal of Applied Ceramic Technology 17, no. 4: 1701-1712.

Research article
Published: 23 September 2019 in ACS Omega
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The feasibility of recovering magnesium from ferronickel slag by vacuum reduction was evaluated. The thermodynamic calculations indicated that the magnesia in slag can be reduced to gaseous magnesium by Si, FeSi, Al, and C, with the minimum reduction temperatures of 2324, 2530, 1678, and 2580 K at 100 000 Pa, respectively. As the system pressure decreases, the minimum reduction temperatures decline significantly. Si maintains the minimum reduction temperature of 1585–1673 K at the atmospheric pressure of 10–100 Pa, acting as a suitable reducing agent for recovering magnesium. To verify the findings, preliminary vacuum reduction experiments, in which CaO was added to eliminate the adverse impact of SiO2 in slag, were carried out. By reducing slag with additions of 50 wt % Si and 30 wt % CaO at 1573 K for 3 h at 10 Pa, the recovery of magnesium reached 97.74%.

ACS Style

Xin Zhang; Foquan Gu; Zhiwei Peng; Liancheng Wang; Huimin Tang; Mingjun Rao; Yuanbo Zhang; Guanghui Li; Tao Jiang; Yang Wang. Recovering Magnesium from Ferronickel Slag by Vacuum Reduction: Thermodynamic Analysis and Experimental Verification. ACS Omega 2019, 4, 16062 -16067.

AMA Style

Xin Zhang, Foquan Gu, Zhiwei Peng, Liancheng Wang, Huimin Tang, Mingjun Rao, Yuanbo Zhang, Guanghui Li, Tao Jiang, Yang Wang. Recovering Magnesium from Ferronickel Slag by Vacuum Reduction: Thermodynamic Analysis and Experimental Verification. ACS Omega. 2019; 4 (14):16062-16067.

Chicago/Turabian Style

Xin Zhang; Foquan Gu; Zhiwei Peng; Liancheng Wang; Huimin Tang; Mingjun Rao; Yuanbo Zhang; Guanghui Li; Tao Jiang; Yang Wang. 2019. "Recovering Magnesium from Ferronickel Slag by Vacuum Reduction: Thermodynamic Analysis and Experimental Verification." ACS Omega 4, no. 14: 16062-16067.

Conference paper
Published: 02 February 2018 in Proceedings of the International Conference on Martensitic Transformations: Chicago
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In our previous study, TiO2 was enriched through stepwise removal of SiO2 and Al2O3 via H3PO4 and NaOH leaching from non-magnetic material, which was derived from reductive roasting of bauxite ore residues with sodium salts followed by magnetic separation. In this research, to elucidate the corresponding mechanism, the effects of reductive roasting with sodium salts on leaching behaviors of non-ferrous elements in bauxite ore residues were further investigated. The logC-pH figures have shown the separation between SiO2 and Al2O3 can be achieved through H3PO4 leaching, and the leaching results proved the difference of leaching ratio between SiO2 and Al2O3 in bauxite ore residues was promoted from 30 to 60% after reductive roasting with sodium salts under the optimal H3PO4 concentration of 1.0 mol/L. TiO2 was found not dissolved after reductive roasting as the leaching ratio changed from 53.9% to be less than 3%, which was due to the insoluble perovskite (CaTiO3) generated in the roasting process. In the NaOH leaching process, the difference between the leaching ratio of Al2O3 and SiO2 in bauxite residue changed from 27.1% to about 60% after reductive roasting under the conditions of maximum Al2O3 extraction ratio with 50.wt% NaOH. The above results have indicated that reductive roasting process with sodium salts was not only favorable to the subsequent separation between SiO2 and Al2O3 as well as the enrichment of TiO2 in H3PO4 leaching process, but also beneficial to extraction of Al2O3 and the separation between Al2O3 and SiO2 in NaOH leaching process.

ACS Style

Bona Deng; Tao Jiang; Guanghui Li; Qing Ye; Foquan Gu; Mingjun Rao; Zhiwei Peng. Effects of Reductive Roasting with Sodium Salts on Leaching Behavior of Non-ferrous Elements in Bauxite Ore Residue. Proceedings of the International Conference on Martensitic Transformations: Chicago 2018, 157 -164.

AMA Style

Bona Deng, Tao Jiang, Guanghui Li, Qing Ye, Foquan Gu, Mingjun Rao, Zhiwei Peng. Effects of Reductive Roasting with Sodium Salts on Leaching Behavior of Non-ferrous Elements in Bauxite Ore Residue. Proceedings of the International Conference on Martensitic Transformations: Chicago. 2018; ():157-164.

Chicago/Turabian Style

Bona Deng; Tao Jiang; Guanghui Li; Qing Ye; Foquan Gu; Mingjun Rao; Zhiwei Peng. 2018. "Effects of Reductive Roasting with Sodium Salts on Leaching Behavior of Non-ferrous Elements in Bauxite Ore Residue." Proceedings of the International Conference on Martensitic Transformations: Chicago , no. : 157-164.

Research article
Published: 02 February 2018 in ACS Sustainable Chemistry & Engineering
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The feasibility of a facile technological route to preparation of refractory materials from a ferronickel slag with addition of sintered magnesia was verified in this study based on the thermodynamics analysis and the experimental exploration of the effect of the sintered magnesia addition on the phase transformation of ferronickel slag during the sintering process. For the first time, the results of thermodynamics calculation, X-Ray diffraction and SEM-EDS analyses revealed that the original phase of the slag can be transformed to high melting point phases by addition of MgO during the sintering process at high temperatures (e.g., 1350 °C). Specifically, the olivine in ferronickel slag decomposed initially, generating a low-iron olivine phase and an enstatite phase. With increasing addition of sintered magnesia, the enstatite phase changed to forsterite, and the iron, aluminum and chromium components in the ferronickel slag converted to high melting point spinel phases, including magnesium aluminum spinel and magnesium chrome spinel via a low-magnesium transient phase. The experimental results showed that a good refractory material with refractoriness of 1660 °C, bulk density of 2.92 g/cm3, apparent porosity of 1.82%, and compressive strength of 100.61 MPa could be obtained when the slag was sintered with addition of 20 wt.% sintered magnesia at 1350 °C for 3 h. Due to the low production cost and property superiority of the prepared refractory material over commercial counterparts, the method proposed in this study is expected to have widespread applications in recycling of ferronickel slag.

ACS Style

Foquan Gu; Zhiwei Peng; Yuanbo Zhang; Huimin Tang; Lei Ye; Weiguang Tian; Guoshen Liang; Mingjun Rao; Guanghui Li; Tao Jiang. Facile Route for Preparing Refractory Materials from Ferronickel Slag with Addition of Magnesia. ACS Sustainable Chemistry & Engineering 2018, 6, 4880 -4889.

AMA Style

Foquan Gu, Zhiwei Peng, Yuanbo Zhang, Huimin Tang, Lei Ye, Weiguang Tian, Guoshen Liang, Mingjun Rao, Guanghui Li, Tao Jiang. Facile Route for Preparing Refractory Materials from Ferronickel Slag with Addition of Magnesia. ACS Sustainable Chemistry & Engineering. 2018; 6 (4):4880-4889.

Chicago/Turabian Style

Foquan Gu; Zhiwei Peng; Yuanbo Zhang; Huimin Tang; Lei Ye; Weiguang Tian; Guoshen Liang; Mingjun Rao; Guanghui Li; Tao Jiang. 2018. "Facile Route for Preparing Refractory Materials from Ferronickel Slag with Addition of Magnesia." ACS Sustainable Chemistry & Engineering 6, no. 4: 4880-4889.

Book chapter
Published: 12 February 2017 in Proceedings of the International Conference on Martensitic Transformations: Chicago
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Bauxite ore residue is a hazardous byproduct derived from alumina production, containing iron, titanium, aluminum and other valuable metals. The feasibility of an integrated technological route for recovering titanium from bauxite ore residue was verified in this study. Titanium-bearing iron concentrate was first recycled through magnetic separation process, and titanium was further leached from the non-magnetic material derived from the upper-stream process by using sulfuric acid. The effects of magnetic intensity on the recovery of iron, and the effects of H2SO4 concentration, leaching temperature, leaching time and liquid to solid ratio on the leaching of titanium have been investigated. The results showed a magnetic concentrate with total iron grade of 56.39% and TiO2 content of 8.66% was obtained under a two-stage magnetic separation process (intensity: 0.8 and 0.2 T, respectively), and magnetic recoveries of iron and titanium attained 55.79 and, 17.37% respectively. 96.36% TiO2 was subsequently leached from the non-magnetic material under the optimal conditions of sulfuric acid concentration of 8 mol/L, leaching temperature of 70 °C, leaching time of 120 min, and liquid to solid ratio of 8.

ACS Style

Guanghui Li; Foquan Gu; Jun Luo; Bona Deng; Zhiwei Peng; Tao Jiang. Recovery of Iron-, Titanium-Bearing Constituents from Bauxite Ore Residue via Magnetic Separation Followed by Sulfuric Acid Leaching. Proceedings of the International Conference on Martensitic Transformations: Chicago 2017, 75 -81.

AMA Style

Guanghui Li, Foquan Gu, Jun Luo, Bona Deng, Zhiwei Peng, Tao Jiang. Recovery of Iron-, Titanium-Bearing Constituents from Bauxite Ore Residue via Magnetic Separation Followed by Sulfuric Acid Leaching. Proceedings of the International Conference on Martensitic Transformations: Chicago. 2017; ():75-81.

Chicago/Turabian Style

Guanghui Li; Foquan Gu; Jun Luo; Bona Deng; Zhiwei Peng; Tao Jiang. 2017. "Recovery of Iron-, Titanium-Bearing Constituents from Bauxite Ore Residue via Magnetic Separation Followed by Sulfuric Acid Leaching." Proceedings of the International Conference on Martensitic Transformations: Chicago , no. : 75-81.

Article
Published: 12 December 2016 in JOM
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In this study, extraction of aluminum-, iron-, and titanium-bearing constituents from diaspore-type bauxite ores was investigated by stepwise treatment consisting of pre-desilication via alkali-leaching of bauxite ore, extraction of alumina via Bayer process, and recovery of iron from red mud via magnetic separation. The pre-desilication results showed that the removal of silica reached 73.92% and that the mass ratio of alumina to silica (A/S) of bauxite concentrate increased from 2.92 to 9.25 under the conditions of sodium hydroxide concentration of 50 wt.%, leaching temperature of 95°C, leaching time of 30 min, and liquid-to-solid ratio of 5 mL/g. A total of 96.31% alumina was extracted from the bauxite concentrate via the Bayer process. Subsequently, by using two-step magnetic separation (intensity: 0.8 T and 0.2 T), TiO2-bearing iron concentrate with total iron grade of 56.39% and TiO2 grade of 8.66% was obtained with recoveries of iron and TiO2 of 55.79% and 17.37%, respectively. The grade of TiO2 reached 21.22% in the nonmagnetic fraction.

ACS Style

Guanghui Li; Foquan Gu; Tao Jiang; Jun Luo; Bona Deng; Zhiwei Peng. Beneficiation of Aluminum-, Iron-, and Titanium-Bearing Constituents from Diasporic Bauxite Ores. JOM 2016, 69, 315 -322.

AMA Style

Guanghui Li, Foquan Gu, Tao Jiang, Jun Luo, Bona Deng, Zhiwei Peng. Beneficiation of Aluminum-, Iron-, and Titanium-Bearing Constituents from Diasporic Bauxite Ores. JOM. 2016; 69 (2):315-322.

Chicago/Turabian Style

Guanghui Li; Foquan Gu; Tao Jiang; Jun Luo; Bona Deng; Zhiwei Peng. 2016. "Beneficiation of Aluminum-, Iron-, and Titanium-Bearing Constituents from Diasporic Bauxite Ores." JOM 69, no. 2: 315-322.