Leaching of Rare Earth Elements from NdFeB Magnets without Mechanical Pretreatment by Sulfuric (H2SO4) and Hydrochloric (HCl) Acids

Klemettinen, Anna; Żak, Andrzej; Chojnacka, Ida; Matuska, Sabina; Leśniewicz, Anna; Wełna, Maja; Adamski, Zbigniew; Klemettinen, Lassi; Rycerz, L.

doi:10.3390/min11121374

Cited by 22 publications

(20 citation statements)

References 46 publications

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“…In our previous study, we proposed a simplified process of hydrometallurgical NdFeB magnet recycling [24]. Its simplicity is a result of omitting the unit operations of crushing, grinding, and roasting before leaching.…”

Section: Introductionmentioning

confidence: 99%

Recovery of Rare Earth Elements from the Leaching Solutions of Spent NdFeB Permanent Magnets by Selective Precipitation of Rare Earth Oxalates

et al. 2023

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After mechanical pre-treatment, the typical hydrometallurgical route of NdFeB magnet recycling starts with leaching in acidic solutions. However, due to the high concentration of iron ions in the leaching solution, the selective recovery of rare earths from the solution is challenging. In our work, the selective precipitation of rare earth oxalates as a potential separation method was proposed. The precipitation of neodymium oxalate was first tested on model solutions, which was then followed by experimental tests carried out on real solutions after the leaching of NdFeB magnets. The recovery of rare earths in the form of oxalates was investigated with the use of different amounts of oxalic acid in relation to its stoichiometric amount. The most efficient separation of rare earths was observed in the case where sulfuric acid was used for leaching. The use of oxalic acid in stoichiometric amounts resulted in the precipitation of about 93% of all rare earths present in the solution, whereas the concentration of Fe and other elements (Ni, Co, and B) practically did not change. An increase in oxalic acid of 20% and 40% more than the stoichiometric amount (100%) led to the increase in the precipitation efficiency of rare earths to 96.7% and 98.1%, respectively. However, the use of oxalic acid in a 1.4 ratio caused a 7% decrease in Fe concentration, which suggests Fe co-precipitation. In order to investigate a possibility of further increasing the separation of rare earths from iron, an additional method was tested, in which iron was first oxidized from Fe2+ to Fe3+ before the precipitation of rare earth oxalates.

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Section: Introductionmentioning

confidence: 99%

Recovery of Rare Earth Elements from the Leaching Solutions of Spent NdFeB Permanent Magnets by Selective Precipitation of Rare Earth Oxalates

et al. 2023

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“…Klemettinen excluding various pretreatment steps, viz., grinding and oxidative roasting. 21 The main aim of the present investigation is to incorporate statistical modeling with a conventional leaching process to study the effect of process parameters on the response variables using response surface methodology−Box Behnken design (RSM-BBD). The study focuses on process optimization and in-depth study of the impact of process parameters on the leaching process, as well as their reciprocal relationships.…”

Section: Introductionmentioning

confidence: 99%

“…It was observed that pretreatment steps such as grinding with NaOH and then roasting at different temperatures aided in selective leaching. Klemettinen et al developed a simplified approach for leaching of REEs from scrap NdFeB magnets by excluding various pretreatment steps, viz., grinding and oxidative roasting …”

Section: Introductionmentioning

confidence: 99%

Design and Optimization Study of Metal Recovery from Scrap NdFeB Magnets Using Response Surface Methodology

Dipali

Prasad

Sahu

et al. 2023

Ind. Eng. Chem. Res.

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The worldwide production of NdFeB magnets has outpaced all other types of magnets owing to their low cost and enhanced magnetic properties. The critical elements required for the production of these magnets are Nd, Pr, and Dy along with other metals. However, the rare earth elements (REEs) come with substantial supply risk. Recycling of REEs from obsolete NdFeB may be a promising alternative to address the supply chain pressure. The purpose of this work is to optimize the water leaching process for the selective recovery of Nd, Pr, Co, and Al from chloride-roasted waste NdFeB magnets, using a statistical approach, and to simultaneously study the effect of significant process variables on the extraction of metals from end-of-life (EOL) magnets. Process optimization was carried out by performing a minimum number of bench scale operations specifically designed for leaching experiments. It was observed that the temperature, time, and pulp density were the most significant process parameters. Tuning of operational parameters was carried out, and model equations were generated for all the response variables with the help of Design Expert software. The response surface methodology (RSM) was used to generate optimized conditions for the leaching process (temperature: 95 °C; pulp density: 100 g/L; time: 60 min), which were further validated by repeating the leaching experiments in triplicate. The extraction efficiency of metal ions was found to be maximum under the optimized leaching conditions.

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“…Various studies have been carried out to investigate the effect of mineral acids leaching reagents, such as sulfuric [6][7][8], hydrochloric [8][9][10], and nitric [10] acids, and organic acids leaching reagents [11][12][13], such as citric, acetic, formic, and tartaric acids, on the leaching efficiency of REPMs. Although the results showed that both types of acids can dissolve the metals in REPMs, environmental issues have caused more attention to be drawn toward using organic acids as green solvents.…”

Section: Introductionmentioning

confidence: 99%

Leaching of Rare Earth Elements from Permanent Magnet Swarf in Citric Acid: Effects of Acid Concentration on Extraction Kinetics

Romano,

Rahmati,

Adavodi

et al. 2023

Metals

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The high demand for rare earth permanent magnets (REPMs) for use in advanced electrical equipment has led to the classification of some rare earth elements (REEs), such as neodymium, praseodymium, and dysprosium, as strategic raw materials by the European Union. Finding an efficient method with economic benefits and minimal environmental impact is one of the challenges of recycling REPMs. A novel method to recover REPM metals by dissolving them with citric acid and separating the rare earth elements using the solvent extraction method as the next step has been introduced. Therefore, this research investigates the efficiency and kinetics of leaching REPM swarf by citric acid (0.5 to 2.5 M). The results showed that increasing the citric acid concentration from 0.5 M to 1.45 M significantly enhanced the dissolving rate of all studied elements. Although the results showed that the optimal concentration of citric acid in the leaching reagent was between 0.9 and 1.45 M, the REE dissolving reaction with a leaching reagent containing 1.45 M and 0.9 M citric acid reached equilibrium conditions at about 120 and 180 min, respectively. It could be concluded that using citric acid as an organic acid can dissolve the metals in REPM swarf with high efficiency and a fast dissolving rate. This issue can be considered key for recycling REPMs and the future REE supply challenge.

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Leaching of Rare Earth Elements from NdFeB Magnets without Mechanical Pretreatment by Sulfuric (H2SO4) and Hydrochloric (HCl) Acids

Cited by 22 publications

References 46 publications

Recovery of Rare Earth Elements from the Leaching Solutions of Spent NdFeB Permanent Magnets by Selective Precipitation of Rare Earth Oxalates

Recovery of Rare Earth Elements from the Leaching Solutions of Spent NdFeB Permanent Magnets by Selective Precipitation of Rare Earth Oxalates

Design and Optimization Study of Metal Recovery from Scrap NdFeB Magnets Using Response Surface Methodology

Leaching of Rare Earth Elements from Permanent Magnet Swarf in Citric Acid: Effects of Acid Concentration on Extraction Kinetics

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