Ultrasound and Microwave assisted leaching of neodymium from waste magnet using organic solvent (original) (raw)
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Acid dissolution of neodymium magnet Nd-Fe-B in different conditions
Bulletin of the University of Karaganda – Chemistry, 2021
The separation of rare-earth elements (REE) from a neodymium magnet has been widely studied last year. During the research it was identified that the waste of computer hard disk contains 25.41 % neodymium, 64.09 % iron, and <<1 % boron. To further isolate rare-earth metals, the magnet was acidically dissolved in open and closed systems. In both methods of dissolution, concentrated nitric acid was used. The difference between these methods is the conditions of dissolution of magnet. The magnet was dissolved in a microwave sample preparation system at different temperatures and pressures in a closed system. In the open system, the acid dissolution of the magnet is conducted at room temperature. 0.2 g of the neodymium magnet sample was taken under two conditions, and the dissolution process in the closed system lasted 1 hour, and in the open system 30-40 minutes. The open system is a non-laborious, simple, and cheap method of dissolving the magnet by comparing both systems. Therefore, an open sample preparation system is used for further work. To remove the iron in the magnet, oxalic acid was used and REEs are precipitated as oxalates under both conditions. According to the result of the Inductively coupled plasma mass spectrometry (ICP-MS) method, it was identified that the neodymium and iron contents in the precipitate are 24.66 % and 0.06 %, respectively. This shows that the iron has almost completely passed to the filtrate.
Leaching kinetics study of neodymium from the scrap magnet using acetic acid
Separation and Purification Technology, 2016
Leaching kinetics of neodymium was investigated from Nd-Fe-B scrap magnet using green solvent as CH 3 COOH. The Characterization study of the scarp magnet was performed by XRD and SEM-EDAX to ascertain the phase as Nd 2 Fe 14 B (31.05 % Nd, 65.15 % Fe and 0.66 % B). Influence of the factors such as CH 3 COOH concentrations (0.05 to 0.8 M), agitation speed (200 to 1000 rpm), particle size (45-150 µm), temperature (308 to 353K) and S/L ratio (1-5% (W/V)) affecting on leaching of Nd was investigated to obtain an optimum condition. Maximum yield (99.99%) of Nd along with definite extraction of Fe was resulted at the condition: Agitation speed: 800 rpm, S/L: 1% (W/V), temp. 353 K, 0.4 M CH 3 COOH and particle size: 106-150 µm). The key factors such as CH 3 COOH concentration and temperature appears to be critical on effective dissolution of both Nd and Fe from the scrap magnet phase. Leaching kinetic results showed best fit with the shrinking-sphere model () ensuring the overall leaching process is governed by surface chemical control mechanism. The activation energy determined from the experimental study was of +17.13 kJ/mol further more supports the proposed chemical control leaching process. Thermodynamics variables like ∆G 0 , ∆H 0 values determined from the Arrhenius plot at varied temperature indicating the feasibility of the leaching reaction of endothermic type. Linear dependence of the plot of log k ap on log 1/d o and a first order dependence of k ap with CH 3 COOH at 0.4M was derived from the above proposed leaching model.
Metals, 2015
The pretreatment processes consisting of grinding followed by roasting were investigated to improve the selective leaching of Nd and Dy from neodymium-iron-boron (NdFeB) magnet scraps. The peaks of Nd(OH)3 and Fe were observed in XRD results after grinding with NaOH as the amount of water addition increased to 5 cm 3. These results indicate that the components of Nd and Fe in NdFeB magnet could be changed successfully into Nd(OH)3 and Fe, respectively. In the roasting tests using the ground product, with increasing roasting temperature to 500 °C, the peaks of Nd(OH)3 and Fe disappeared while those of Nd2O3 and Fe2O3 were shown. The peaks of NdFeO3 in the sample roasted at 600 °C were observed in the XRD pattern. Consequently, 94.2%, 93.1%, 1.0% of Nd, Dy, Fe were leached at 400 rpm and 90 °C in 1 kmol• m −3 acetic acid solution with 1% pulp density using a sample prepared under the following conditions: 15 in stoichiometric molar ratio of NaOH:Nd, 550 rpm in rotational grinding speed, 5 cm 3 in water addition, 30 min in grinding time, 400 °C and 2 h in roasting temperature and time. The results indicate that the selective leaching of Nd and Dy from NdFeB magnet could be achieved successfully by grinding and then roasting treatments.
Leaching kinetics of neodymium in sulfuric acid from E-scrap of NdFeB permanent magnet
Korean Journal of Chemical Engineering, 2014
The leaching kinetics of neodymium in NdFeB permanent magnet powder was analyzed for the purpose of recovery of neodymium in sulfuric acid (H 2 SO 4) from E-scrap (electric scrap) of NdFeB permanent magnet powder treated by oxidation roasting to form a reactant. The reaction was conducted with H 2 SO 4 concentrations ranging from 2.5 to 3.5 M, a pulp density of 110.8 g/L, an agitation speed of 750 rpm, and a temperature range of 30 to 70 o C. After 4 h of leaching, the neodymium content in the E-scrap powders was completely converted into a neodymium sulfate (Nd 2 (SO 4) 3) solution phase in H 2 SO 4 in the condition of 70 o C and 3.0 M H 2 SO 4. Based on a shrinking core model with sphere shape, the leaching mechanism of neodymium was determined by the rate-determining step of the ash layer diffusion. Generally, the solubility of pure rare earth elements in H 2 SO 4 is decreased with an increase in leaching temperatures. However, the leaching rate of the neodymium in E-scrap powders increased with the leaching temperatures in this study because the ash layer included in the E-scrap powder provided resistance against the leaching. Using the Arrhenius expression, the apparent activation energy values were determined to be 2.26 kJmol −1 in 2.5 M H 2 SO 4 and 2.77 kJmol −1 in 3.0 M H 2 SO 4 .
Effect of Scrap Size on Extraction of Neodymium from Nd-Fe-B Magnet Scrap by Liquid Metal Extraction
Current Nanoscience, 2014
The effects of Nd-Fe-B magnet scrap size on extraction behavior were investigated by liquid metal extraction using molten Mg. The magnet scraps with Mg were placed into a stainless steel crucible and then heated to 1,073K for 10 to 50min. The amount of extracted Nd after liquid metal extraction process was increased with an increasing with holding time and scrap size, and the maximum contents of Nd in Mg were observed to be about 24.2 wt.% in the conditions of the 5mm sized scrap heated for 50min. It was revealed that Nd oxides existing in the magnet scraps prevent the dissolution of Nd into Mg.
An innovative environmental process for the treatment of scrap Nd-Fe-B magnets
Journal of Environmental Management, 2020
Strict environmental regulations as well as requirement of conservation of natural resources compelled the researchers to recycle the metal values from secondary resources. The scrap magnets found to be a potential alternative resource to extract rare earth metal, Nd. Present paper reports a novel process flow-sheet for the recycling of scrap Nd-Fe-B magnets to recover Nd as marketable salt and other valuable by-products. The Nd-Fe-B magnets were demagnetized, crushed and charged to atmospheric leaching resulting in ~99.99% recovery of REMs (Nd, Pr, Dy) and Fe using 1 M H 2 SO 4 solution at room temperature for 90 min and pulp density 50 g/L. The obtained leach liquor was subjected to acid extraction procedure by mixing the liquor with 70% TEHA diluted in kerosene for 10 min, which requires five stages for complete extraction of acid from the liquor having O/A ratio 2:1. Ammonia solution was used to increase the pH of acid free leach liquor to 1.65 for the precipitation of Nd (with minor amount of Pr and Dy) and above that to precipitate Fe. Further, processing of these valuables make them industrially applicable. The leached residue was checked using Toxicity Characteristics Leachability Procedure (TCLP) test and found the remained metals within the permissible limit. This process offers a simple and efficient means to reduce the toxicological effect by recovering Nd from magnets of computer hard disks.
Recovery of neodymium and dysprosium from NdFeB magnet swarf
Hydrometallurgy, 2017
The rare earth elements neodymium and dysprosium were separated and recovered from NdFeB permanent magnet swarf by hydrometallurgical route. The magnet swarf was leached with HCl after crushing and grinding, and from the leach liquor, Nd and Dy were separated by solvent extraction using NaCyanex 302. The separation factor (β) of Dy/Nd with NaCyanex 302 was high at low equilibrium pH. So Dy was first separated from the leach liquor at pH 0.5 (equilibrium pH 1.2). After separation of Dy, the separation of Nd was also carried out with the same extractant. The effect of equilibrium pH and extractant concentration on the extraction of Nd and Dy with NaCyanex 302 was studied. The McCabe-Thiele plots for extraction of both Dy and Nd with NaCyanex 302 were constructed and the number of stages for quantitative extraction was determined. The stripping of loaded organic was carried out with three different mineral acids and it was observed that the stripping efficiency followed the order HCl < HNO 3 < H 2 SO 4. The McCabe-Thiele plots for stripping of loaded organic were also constructed. The reaction mechanism of both Nd and Dy was determined from the slope analysis method and the extracted species was found to be MA 3 .5HA.
Liquid metal extraction of Nd from NdFeB magnet scrap
Journal of Materials Research, 2000
This research involves using molten magnesium (Mg) to remove neodymium (Nd) from NdFeB magnet scrap by diffusion. Mg was melted over pieces of NdFeB scrap and held at temperatures in the range 675–705 °C for 2–8 h. The Mg was allowed to solidify, and the castings were then sectioned and characterized using scanning electron microscopy, x-ray diffraction, and chemical analysis. Nd was found to have diffused out of the solid scrap into the molten Mg. The thickness of the diffusion layer was measured, the diffusion of Nd through the NdFeB scrap into liquid Mg was described, and the diffusion coefficient of Nd in liquid Mg was estimated.
International Journal of Environmental Science and Technology, 2018
Nickel is one of the heavy metals, which is discharged to ecosystem by normal process and human actions. Nickel is regarded as crucial ion in the living creature and is a component of protein structure at very low level. Dispersive micro-solid-phase extraction assisted by ultrasonic waves with a new magnetic material using pyridine-functionalized magnetic nanoporous sorbent was utilized for detection of nickel ions at trace levels in real matrices. Magnetized nanoporous silica (MCM-41) was modified with pyridine groups, and the structure of prepared magnetic nanoporous sorbent was confirmed by instrumental techniques. The applied techniques were Fourier-transformed infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy and thermogravimetry-differential thermal analysis. Preconcentrated nickel using the mentioned sample preparation procedure was monitored by GFAAS at ng L −1 concentrations. To optimize the effect of significant parameters on sorption and desorption of nickel ions using the applied sample preparation procedure, Box-Behnken design was utilized. The influencing parameters in the sorption step are: sorption amount (mg), pH of solution and sonication time (min), and these parameters for desorption step are: volume of eluent (mL), concentration of eluent (mol L −1) and sonication time (min). Optimized data for parameters that obtained by Box-Behnken design were: sample's pH: 7.5, sonication time for sorption: 8 min, sorbent amount: 24 mg, desorption solvent: HCl 1.2 mol L −1 , eluent volume: 420 μL and time of sonication for desorption, 8 min. Relative standard deviation and method detection limit for nickel monitoring under optimized conditions by UA-d-μSPE were observed to be < 6% and 0.008 μg L −1 , respectively. Keywords Ultrasonic-assisted dispersive micro-SPE • Pyridine-functionalized magnetic MCM-41 • Box-Behnken design • Nickel ions • Water samples and food media Editorial responsibility: Necip Atar.
Recycling
This research investigated recycling of manufacturing NdFeB magnet wastes in as-sintered and powder forms which contained high carbon via pyro-hydro metallurgy process. Effects of oxidative roasting on selective leaching of the magnet wastes were the main focus in comparison to recycling via whole leaching without oxidative roasting. The process started from oxidative roasting at 600 °C, sulfuric leaching, drying, roasting at 750 °C for powder and 800 °C for sintered wastes, water leaching, oxalic acid precipitation and calcination at 1000 °C to obtain neodymium oxides. Oxidative roasting was found to reduce carbon and resulted in neodymium and iron oxide formation with a minimum amount of neodymium iron oxide. This provided effective selective leaching of neodymium. For whole leaching, a significant loss of neodymium into leached residue was observed. Oxidative roasting-selective leaching provided significant recovery in the amount of 75.46% while whole leaching resulted in only 31...