JOURNAL OF ENVIRONMENTAL MANAGEMENT
·
2026
·
IF 9.2
Xuheng Liu,Ziming Cao,Zhongwei Zhao,Xingyu Chen,Jiangtao Li,Lihua He,Fenglong Sun,Wenjuan Zhang
Securing reliable supplies of rare-earth elements (REEs) increasingly depends on efficient recycling, as primary production remains geopolitically concentrated while demand from advanced technologies continues to grow. However, recycling of NdFeB waste continues to rely on conventional hydrometallurgical and pyrometallurgical processes, which are waste generating due to the intrinsic challenge of separating REEs from iron-rich phases. Here, we demonstrate a ZnCl 2 -assisted chlorination strategy that selectively converts Nd into an acid-soluble NdOCl, while stabilizing Fe as insoluble oxides (ZnFe 2 O 4 and Fe 2 O 3 ), thereby suppressing co-dissolution and facilitating efficient REEs−Fe separation. Thermodynamic analysis identifies atmosphere and temperature as critical parameters governing phase evolution. Experimental validation confirms that, under optimized conditions (air, 700 °C), REEs recoveries reach 99.31% (Nd), 93.85% (Dy), and 98.82% (Pr), while Fe dissolution is limited to 2.30%. In contrast, inert atmospheres promote Fe dissolution, and temperatures ≥800 °C induce NdFeO 3 formation, both of which compromise selective recovery. Kinetic analysis further reveals a nucleation-and-growth controlled mechanism consistent with the Avrami–Erofeev model. This route thus offers a streamlined and reagent-efficient process for REEs recovery from waste NdFeB, offering a scalable route toward closing the REEs supply loop.
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PubMed
高影响因子
SOLVENT EXTRACTION AND ION EXCHANGE
·
2025
·
IF 2.1
Yang Li,Boren Tan,Long Meng,Peilin Wang,Shirong Chen,Tao Qi,Yong Wang
The production of neodymium-iron-boron (NdFeB) magnet scraps has been increasing, creating an urgent demand for the recovery of rare earths elements from these scraps. Focus on the NdFeB acid leachate – saponified 2-ethylhexyl hydrogen −2-ethylhexylphosphonate (PC-88A) system, this study investigated mass transfer and hydrodynamics in a pulsed disc and doughnut column. Studies on mass transfer of single droplets demonstrated that the mass transfer process from the aqueous phase to the organic phase was enhanced when aqueous droplets serve as dispersed phase. The dispersed phase holdup (xd) and droplet diameter (d32) within the pulsed disc and doughnut column (PDDC) was investigated using NdFeB acid leachate as the dispersed phase. Results indicated that the xd decreased initially and increased subsequently with the increasing pulse intensity, and increased with the increment of flow rate. The evolution of d32 was inversely related to pulse intensity. The xd and d32 of dispersed phase were predicted with average absolute relative errors of 10.76% and 17.37%, respectively. The extraction efficiency of total REEs was 36.15% and mass transfer unit height reached 2 m of PDDC under an optimal condition. Based on estimation, a PDDC with a height of 2 m could realize the complete extraction of total REEs.
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高影响因子
ADVANCED FUNCTIONAL MATERIALS
·
2022
·Vol. 33
·期 11
·2210961
·
IF 19.924
Yongyu Lu,Dehai Yu,Haoxuan Dong,Sen Chen,He Zhou,Lichen Wang,Zhongshan Deng,Zhizhu He,Jing Liu
Leakage is a significant issue that prevents the widespread application of liquid metals (LMs) and an effective solution has not yet been developed. One potential solution is to use the high surface tension of LMs to encapsulate them in a porous material. However, it is challenging as it is difficult to infuse LMs into tiny pores. This study proposes a bottom-up strategy where LMs are doped with NdFeB@Ag particles, which are then magnetized to form a tight porous structure. This structure is robust and resistant to collapse under mechanical deformation. Therefore, LMs can be reliably immobilized within the pores between the particles, and a dynamic leakage-free state is achieved. The encapsulated LMs demonstrate excellent properties including a large latent heat of 153.46 J cm −3 , high thermal conductivity of 35.62 W m −1 K −1 , and enhanced electrical conductivity of 69.61%, which efficiently extends their functional scope and potential value.
研究领域:
材料科学
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工程学
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热能工程
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电气工程
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高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2026
·
IF 12.5
Mengfan Hu,Zhining Huang,Peihua Zhang,Nanliang Chen,Jinhua Jiang,Shaoju Fu
Magnetoelectrical textiles, as self-power device to generate energy from motions, are promising building blocks for wearable electronic fields, but these traditional strategies towards magnetoelectrical textiles still suffer from insufficient stability and reliability, and the large-scale fabrication of magnetoelectrical textiles still remains challenging. Herein, soft magnetic fiber and its knitted fabric based NdFeB@ZIF-8 composite particles were proposed, and their electro-magnetic response performances were comprehensively characterized. NdFeB@ZIF-8 composite particles were synthesized, and they exhibited excellent magnetic property with the remnant magnetization (Mr) and coercivity (Hc) at 80 emg/g and 8604 Oe, respectively, the Ms. of NdFeB@ZIF-8 particles was 113.5 emu/g. The magnetoelectrical fibers prepared by micro-controlled flow spinning technology exhibited a breaking elongation of 575%. Driven by an external magnetic field, the magnetoelectrical fibers could bend up to 43°, and moved easily in tiny tube and lift a weight of 20 g. Similarly, the magnetoelectrical fabrics can undergo various deformations. Moreover, the magnetoelectric power generation system delivered a continuous and stable output voltage, allowing the generation of a stable electrical signal of 15 mV under various external forces. The maximum output peak power density was 551.25 mW/m2 when the resistance of the external load was 1 Ω. The presence of a magnetic field endowed magnetic fabrics with a certain degree of electromagnetic shielding effectiveness. In sum, this study employed an efficient and environmentally friendly fabricating strategy for magnetoelectrical textiles with self-power ability, showing great potential for the wearable electronics application.
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高影响因子
RSC Advances
·
2024
·Vol. 14
·期 13
·8641-8651
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IF 3.9
Li Xiaoya,Ma Yongcun,Peng Shusen,Tian lixi
The traditional aqueous electroplating of zinc film causes significant corrosion of NdFeB during the electroplating process, which is accompanied by hydrogen evolution reactions. In this study, electroplating zinc film is carried out from a chloride-free nonaqueous bath using zinc acetate (Zn(OAc)2) as the main salt, sodium acetate (NaOAc) as the conducting salt, and ethylene glycol (EG) as the solvent. The electrochemical properties of the EG bath with Zn(OAc)2 and NaOAc are characterized by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV) together with a Hull cell test on brass. The results of the experiment show that the Zn(OAc)2 concentration, current density, and temperature significantly impact the deposition behavior of zinc. Moreover, the open circuit potential (OCP) test and scanning electron microscopy (SEM) results demonstrated that the corrosion of NdFeB in the EG bath containing 0.7 M Zn(OAc)2 and NaOAc is effectively inhibited compared to when using the traditional aqueous zinc plating bath. A dense zinc film with a metallic appearance is successfully deposited on the NdFeB surface from the EG bath containing 0.7 M Zn(OAc)2 and NaOAc at 6 mA cm−2 and 60 °C. Comparative experiments demonstrate that the as-deposited Zn film exhibits superior protective performance and exerts less damage to NdFeB compared to the aqueous electroplating film.
研究领域:
材料科学
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电化学
·
表面工程
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PubMed
高影响因子
Journal of Cleaner Production
·
2026
·
IF 10.7
Jianru Li,Cunying Xu,Rui Luo,Qibo Zhang,Yixin Hua,Mingyuan Gao,Rongrong Deng,Mengwei Guo,Yan Li
A water-regulated DES strategy was developed for recovery NdFeB scrap. • REEs and Fe are directly separated and recycled in ChCl-OA-H 2 O DES. • REE recovery reached 97% at a solid/liquid ratio of 100 g L −1 . • Even after 10 cycles, the recycling efficiency of DES remains above 90%. • Purity of REE oxalate and FeC 2 O 4 ·2H 2 O respectively exceeds 98.8% and 97.5%. The efficient recycling of rare earth elements (REEs) from waste neodymium-iron-boron (NdFeB) magnets is critical for supply chain security and environmental sustainability. However, conventional recycling methods face significant challenges due to complex separation procedures, excessive reagent consumption, and the generation of substantial quantities of secondary waste. This study develops an efficient and green process for the sequential recovery of high-purity mixed REEs (primarily Nd, Pr, Ce) and iron (Fe) from waste NdFeB magnets, utilizing a water-regulated choline chloride-oxalic acid (ChCl-OA-H 2 O) deep eutectic solvent (DES). After calcination pretreatment selectively converts the NdFeB alloy into soluble REE 2 O 3 and Fe 2 O 3 , Response surface methodology (RSM) was employed to optimize the leaching process. Under the identified optimized conditions (water content: 39.56%, solid/liquid ratio: 98.15 g/L, temperature: 91.06°C, time: 12.07 h), leaching efficiencies reached 97.81% for Nd and 99.23% for Fe. The DES system demonstrated excellent recyclability, maintaining >90% Nd recovery over ten cycles without significant performance loss. Mechanistic studies indicate that ChCl-OA has the dual functionality: selective precipitation of REE 3+ as insoluble oxalates REE 2 (C 2 O 4 ) 3 ·10H 2 O, and complexation of Fe 3+ as soluble [Fe(C 2 O 4 ) 3 ] 3- . The dissolved [Fe(C 2 O 4 ) 3 ] 3- is subsequently recovered from the filtrate as high-purity FeC 2 O 4 ·2H 2 O (97.52%) via UV-Vis photoreduction. Besides, water addition strategically reduces DES viscosity, overcoming the mass transfer limitations that plague conventional DES systems. This work establishes a sustainable, closed-loop pathway for the comprehensive valorization of NdFeB waste, directly addressing the critical trade-off between recovery efficiency and environmental impact in rare earth recycling. Download: Download high-res image (328KB) Download: Download full-size image
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SEPARATION AND PURIFICATION TECHNOLOGY
·
2025
·
IF 9
Yang Li,Jieliang Chen,Long Meng,Shirong Chen,Boren Tan,Tao Qi,Yong Wang
The pulse disc and doughnut columns (PDDC) require high energy input when dealing with systems where the dispersed phase is difficult to break, which limits its application. To address this, a novel extraction column, pulsed sieve − disc and doughnut column (PSDDC) was designed. The hydrodynamics and extraction performance in the PSDDC were investigated systematically using neodymium-iron-boron (NdFeB) magnet scraps acid leachate–PC-88A extractant system. The results indicated that inducing sieve plates effectively reduced droplet size at a mild pulse intensity. Furthermore, compared with the required pulse intensity of 1.5 cm/s to shift operation zone from mixer-settler zone to emulsion zone in PDDC, PSDDC only required 1.0 cm/s. In the mixer-settler zone, the dispersed phase holdup ( x d ) values were comparable in both columns, while in the emulsion zone the x d values in PSDDC were higher than those in PDDC. At a medium pulse intensity of 1.5 cm/s, the extraction performance of rare earth elements (REEs) in the PSDDC was enhanced, with an extraction efficiency of 65.19 %, representing a 6-fold increase over the PDDC. Additionally, new correlations were established for the Sauter mean droplet size ( d 32 ), x d and mass transfer coefficients of dispersed phase ( K od ) in PSDDC, yielding average relative residual errors ( AARE s) of 9.43 %, 10.96 %, and 10.04 %, respectively. Briefly, compared with PDDC, PSDDC exhibited excellent extraction performance for REEs in the NdFeB acid leachate–PC-88A system.
研究领域:
化学工程
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湿法冶金
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资源回收
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分离科学
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环境工程
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材料循环利用
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高影响因子
JOURNAL OF RARE EARTHS
·
2020
·
IF 3.104
Zhengyu Liu,Jiaming Wu,Xinyu Liu,Wen Wang,Ziwei Li,Ruijing Xu,Yue Ding,Junlian Wang
Rare earths (REs) and Co are critical strategic resources. Their recovery is crucial for ensuring that their supplies are adequate and for reducing environmental pollution. End-of-life NdFeB magnets are important secondary RE sources. The separation of Dy, Nd, and Co from NdFeB leachate using a relatively new extractant (2,3-dimethylbutyl) (2,4,4′-trimethylpentyl)phosphinic acid (INET-3), was investigated in this study. The separation parameters, such as equilibrium pH, phase ratio, INET-3 concentration, and number of counter-current extraction stages, were optimised. The results show that INET-3 can separate Dy, Nd, and Co efficiently. For the preferential extraction of Dy from synthetic iron-free NdFeB leachate, the optimum equilibrium pH is 2.60. Under this condition, separation of Dy from the leachate requires four counter-current extraction stages at A/O (volume ratio of aqueous to organic) = 1:2. This is demonstrated by a simulated four-stage counter-current extraction process. At equilibrium pH = 2.52 and A/O = 1:2, 98% of Dy is recovered with 95% purity. As to the subsequent separation of Nd from the leachate, nearly 100% is recovered with 99% purity through a simulated three-stage counter-current extraction process at equilibrium pH = 5.33 and A/O = 1:1. Approximately 95% of Co remains in the raffinate with 99.98% purity.
研究领域:
资源回收
·
化学工程
·
环境科学
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高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2022
·
IF 9.136
Chang Du,Shuai Ma,Meiying Xie,Fan Yang,Zhigang Zhao,Yun Chen,Ying Ma
This paper proposes a new integrated method for recycling permanent magnet waste by betaine hydrochloride ([Hbet]Cl) solution extraction. The orthogonal experiment method was used to analyze four factors in the leaching process to explore the primary and secondary factors influencing the leaching results. The following optimum leaching conditions were obtained: leaching temperature of 200 ℃, leaching time of 8 h, lixiviant [Hbet]Cl concentration of 0.2 mol/L, and solid–liquid ratio of 1:150 g/ml. These conditions yielded the optimum leaching results of 99.81 % Pr, 97.05 % Nd, 95.51 % Gd, 56.24 % Ce and 0.20 % Fe, and almost all iron oxide remained in the residue. Compared with the results for common lixiviants, the proposed method showed a better leaching rate and selectivity, and the leaching sequence was in line with established chemical properties. The method is characterized by a high recovery rate, strong selectivity, environmental friendliness and low cost. The leaching mechanism was analyzed, and the crystal lattice energy U values of ionic crystal decomposition were calculated to explain the dissolution sequence and solubility difference of metal oxides, laying a foundation for the recovery process.
研究领域:
材料科学
·
环境科学
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高影响因子
HYDROMETALLURGY
·
2025
·
IF 5.3
Jun Li,Ruihui Wu,Shengjun Tian,Ronghao Liu,Huiying Wei,Yanzhao Yang
The NdFeB magnets are the most widely used permanent magnetic materials in the international arena, and the recovery of Nd(III) from the growing number of waste-NdFeB magnets is becoming increasingly crucial. In this study, a novel synergistic extractant consisting of bis(2,4,4-trimethylpentyl) phosphonic acid (Cyanex 272) and 8-hydroxyquinoline (8-HQ) is proposed for the recovery of Nd(III) from waste-NdFeB magnets. First, the influence of the ratio of the two extractants on the synergistic extraction coefficient was investigated. The coextraction coefficient ratio of the two extractants Cyanex 272 and 8-HQ was 1:1. The extraction behaviors under different conditions, such as the extractant concentration, aqueous phase pH (pH = 5), and oscillation time (1 min), were investigated. Under optimal conditions, the extraction efficiency reached 99.6 %. A chelating extraction mechanism was proposed on the basis of UV–vis spectroscopy, FT-IR spectroscopy, and NMR spectroscopy methods. The excellent extraction efficiency was maintained after five cycles of extraction and stripping, indicating the potential for application in light and heavy rare earth separation processes. Overall, this study aims to provide a new economically viable method for the recovery of Nd(III) from waste-NdFeB magnets.
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高影响因子
WASTE MANAGEMENT
·
2019
·
IF 5.431
X. Zhou,Y.L. Tian,H.Y. Yu,H. Zhang,X.C. Zhong,Z.W. Liu
The present work provides a facile and energy-saving approach to recycle Nd-Fe-B wastes. Employing the severely oxidized and contaminated sintered Nd-Fe-B scraps as the raw materials, sub-micro sized Nd-Fe-B/α-Fe composite magnetic powders were successfully synthesized by microwave assisted auto-combustion method followed by a reduction diffusion process. In details, the waste magnets were dissolved in HNO 3 solution and both the rare earth oxides and iron oxide were obtained by auto-combustion approach with the help of microwave heating. These oxides were then reduced to achieve Nd-Fe-B alloys with the reducing agent CaH 2 . To modify the composition of the final product, Nd(NO 3 ) 3 ·6H 2 O and H 3 BO 3 were added during dissolving and consequently three compositions of the final products were obtained. TEM results demonstrate that the sizes of α-Fe and Nd 2 Fe 14 B grains are below 10 nm and 20 nm, respectively. The magnetic properties of the composite powders obtained from the wastes in this study are comparable to those obtained by other methods using pure reagents. The room temperature coercivity of as-synthesized Nd 15 Fe 77 B 8 is higher than 400 kA/m. In addition, an appropriate mass ratio of CaH 2 to Nd-Fe-B oxides is required in order to obtain good magnetic properties.
研究领域:
材料科学
·
磁性材料
·
回收技术
·
稀土利用
·
纳米材料合成
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高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2019
·
IF 5.107
Yusheng Yang,Chaoqun Lan,Yingcai Wang,Zengwu Zhao,Baowei Li
In this work, a simple and sustainable approach is proposed to recover rare earths and iron from an ultrafine NdFeB waste. Rare earths are directly recovered by one-step precipitation in hydrofluoric acid and the dissolved iron by electrodeposition. The rate constant and activation energy of the reaction of rare earth hydroxide with hydrofluoric acid are investigated to understand the kinetics of iron leaching and rare earth precipitation. The rare earth precipitation is much faster than the iron leaching, enabling the rare earths separation from iron after a complete iron dissolution. The cathodic deposits of iron were characterized by X-ray photoelectron spectrometer (XPS) and scanning electron microscope (SEM). The nano-scale FeF 2 (s) and Fe(s) were deposited on Pt electrode in hydrofluoric acid solution with pH 2.3 and pH 2.89, respectively. The reduction of Fe(III) to Fe(0) was investigated by cyclic voltammetry, chronopotentiometry and open circuit chronopotentiometry. This reduction was a quasi-reversible process which was controlled by diffusion. The temperature dependence of the diffusion coefficient was established as lnD = −9.84 − 1805.43/ T and the activation energy value of the diffusion process was calculated to be −15.01 kJ mol −1 . The relationship between the Gibbs energy of intermetallic Fe-Pt formation and the temperature was established to be Δ G = −487.53 + 0.936 T . The hydrofluoric acid after the electrodeposition could be recycled for the leaching of the ultrafine NdFeB waste again.
研究领域:
材料科学
·
环境工程
·
电化学
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高影响因子
危险品化学品经营许可证（带存储）