| 1. |
- Gergoric, Marino, 1989, et al.
(författare)
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Leaching and recovery of rare-earth elements from neodymium magnet waste using organic acids
- 2018
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- Over the last decade, rare-earth elements (REEs) have become critical in the European Union (EU) in terms of supply risk, and they remain critical to this day. End-of-life electronic scrap (e-scrap) recycling can provide a partial solution to the supply of REEs in the EU. One such product is end-of-life neodymium (NdFeB) magnets, which can be a feasible source of Nd, Dy, and Pr. REEs are normally leached out of NdFeB magnet waste using strong mineral acids, which can have an adverse impact on the environment in case of accidental release. Organic acids can be a solution to this problem due to easier handling, degradability, and less poisonous gas evolution during leaching. However, the literature on leaching NdFeB magnets waste with organic acids is very scarce and poorly investigated. This paper investigates the recovery of Nd, Pr, and Dy from NdFeB magnets waste powder using leaching and solvent extraction. The goal was to determine potential selectivity between the recovery of REEs and other impurities in the material. Citric acid and acetic acid were used as leaching agents, while di-(2-ethylhexyl) phosphoric acid (D2EHPA) was used for preliminary solvent extraction tests. The highest leaching efficiencies were achieved with 1 mol/L citric acid (where almost 100% of the REEs were leached after 24 h) and 1 mol/L acetic acid (where >95% of the REEs were leached). Fe and Co—two major impurities—were co-leached into the solution, and no leaching selectivity was achieved between the impurities and the REEs. The solvent extraction experiments with D2EHPA in Solvent 70 on 1 mol/L leachates of both acetic acid and citric acid showed much higher affinity for Nd than Fe, with better extraction properties observed in acetic acid leachate. The results showed that acetic acid and citric acid are feasible for the recovery of REEs out of NdFeB waste under certain conditions.
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| 2. |
- Gergoric, Marino, 1989, et al.
(författare)
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Characterization and Leaching of Neodymium Magnet Waste and Solvent Extraction of the Rare-Earth Elements Using TODGA
- 2017
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Ingår i: Journal of Sustainable Metallurgy. - : Springer Science and Business Media LLC. - 2199-3831 .- 2199-3823. ; 3:3, s. 638-645
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Tidskriftsartikel (refereegranskat)abstract
- The rare-earth elements (REEs) are considered as some of the most critical elements in the EU and the USA today. E-scrap, such as end-of-life neodymium magnets, could be a viable secondary source for the recovery of these elements. Neodymium magnets (NdFeB) consist of considerable amounts of Nd, Dy, Pr, and some other REEs, depending on the specific application. Apart from REEs, neodymium magnets are made up of around 60% iron, which can pose a challenge in their recycling. For example, iron can be dissolved along with other elements during leaching or co-extracted during solvent extraction. In this work, extraction of REEs with TODGA (tetraoctyl-diglycolamide) from a real leachate, obtained by neodymium magnet powder dissolution in nitric acid, was studied. The goal was to selectively extract the REEs from other elements in the solution. TODGA was used as the extracting agent due to its selective extraction properties for REEs and other f-block elements. The influence of the diluent on the overall extraction and the selectivity of the extraction was studied in order to determine application feasibility of future processes. To this end, experiments using Solvent 70 (hydrocarbons C11-C14, ae 0.5 wt% aromatics), hexane, toluene, cyclohexanone and 1-octanol as the diluents were performed. TODGA has shown good selectivity between REEs and other elements in solution under almost all conditions, reaching the highest distribution ratios of REEs in the aliphatic diluents, while the distribution ratios of other non-REEs reach a mere value of 0.1. An exception was cyclohexanone, which has the ability to extract small amounts of ions itself. The highest separation factors between Dy and the light REEs (Nd and Pr) were observed with a 0.01 M solution of TODGA in Solvent 70. REEs, as group, were extracted with 0.1 M solutions of TODGA in all diluents except for cyclohexanone, which led to extraction of Al and B at amounts greater than 10%. Stripping with over 98% efficiency was achieved using MQ water in one step.
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| 3. |
- Gergoric, Marino, 1989
(författare)
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Hydrometallurgical Treatment of Neodymium Magnet Waste
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent decades have seen a considerable increase in the usage of rare-earth elements (REEs) in modern technologies and green energy sources. Recycling of REEs out of end-of-life products and E-scrap has become an alternative to mining them out of primary ores due to their supply risk in some countries and the development towards circular economies. Neodymium (NdFeB) magnets are of special interest since they are present in various technological waste streams. They contain considerable amounts of REEs such as Nd, Dy, Pr and some others, for example Gd and Tb, depending on the specific application, making them very attractive for REE-recycling. Apart from REEs, neodymium magnets are made up of around 60% iron, which can pose a challenge in their recycling. Hydrometallurgical methods such as leaching and solvent extraction are attractive and efficient methods for the recovery of REEs out of NdFeB magnets, albeit with certain drawbacks such as large aqueous and organic waste generation during the process and utilization of some hazardous chemicals. The REEs are normally leached out of the NdFeB magnet waste using strong mineral acids such as HCl, HNO3 and H2SO4 but, despite their excellent leaching properties for REEs out of NdFeB magnets, they pose some risk to the environment because there are still issues with poisonous gas evolution during leaching, regeneration of the used acids, and handling of highly concentrated acids can be a challenge. Furthermore, the extracting agents currently used in the industry for REE-extraction are mostly phosphorus-based and do not follow the CHON principle, meaning it is not possible to incinerate them without either the production of ash or acidic gases. In this work a comparison of leaching efficiency between the traditionally used mineral acids and organic lixiviants was performed. Magnet powder was successfully leached using fully combustible organic lixiviants (including acetic, citric, maleic, glycolic and ascorbic acid), and new green leaching alternatives were developed. Parameters including acid concentration, leaching time, S/L ratio and temperature were investigated and mitigated. Subsequently, the REEs were selectively extracted from these leachates. For this separation step several phosphorus-based extractants (TBP, D2EHPA, Cyanex 272 and 923) were investigated, alongside TODGA, which follows the CHON principle. The influence of various diluents on the extraction was also studied. It was concluded that REEs can be separated into relatively pure aqueous streams using organic acids instead of mineral acids under certain conditions, while TODGA was efficient at separating REEs from large amounts of Fe in these particular waste streams. A process for the extraction of REEs from organic acids leachates was developed, with promising results.
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| 4. |
- Gergoric, Marino, 1989, et al.
(författare)
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Separation of Heavy Rare-Earth Elements from Light Rare-Earth Elements Via Solvent Extraction from a Neodymium Magnet Leachate and the Effects of Diluents
- 2017
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Ingår i: Journal of Sustainable Metallurgy. - : Springer Science and Business Media LLC. - 2199-3831 .- 2199-3823. ; 3:3, s. 601-610
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Tidskriftsartikel (refereegranskat)abstract
- In recent decades, rare-earth elements (REEs) have seen a considerable increase in usage in modern technologies and the so-called green energy sources. The REEs are currently regarded to be among the most critical elements by the European Union (EU) and the United States (USA). Large investments are made in the research of recycling of the REEs from end-of-life products and E-scrap. One potential source for recycling of larger amounts of neodymium and dysprosium are end-of-life neodymium magnets. In this work, the selective extraction of REEs from a sulfuric media leachate (containing Nd, Dy, Pr, Gd, Co, and B) obtained by selective roasting of NdFeB waste and leaching was investigated. The extracting agent D2EHPA (di-(2-ethylhexyl) phosphoric acid) diluted in Solvent 70, hexane, octane, cyclohexanone, chloroform, 1-octanol, and toluene was used for the investigation of the effects of using different diluents on the extraction of REEs and the separation between the light and the heavy REEs. The concentrations of D2EHPA in the used diluents were 0.3, 0.6, 0.9, and 1.2 M. The highest separation factors between the heavy and the light REEs were achieved using 0.3 M D2EHPA in hexane, while no B or Co extraction was measurable. The REEs were completely extracted as a group using 0.9 M or 1.2 M D2EHPA in either octane or hexane, also with no B or Co extraction. The aliphatic nonpolar diluents showed better properties than the aromatic and polar ones. The complete stripping of REEs from the loaded organic phases was proven to be efficient using hydrochloric acid at concentrations of 2 M or higher.
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| 5. |
- Gergoric, Marino, 1989
(författare)
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The Diluent Effect on the Solvent Extraction of Rare Earth Elements from Neodymium Magnet Leachate
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The diluent effect on the solvent extraction of rare earth elements from neodymium magnet leachateMARINO GERGORIĆIndustrial Materials RecyclingDepartment of Chemistry and Chemical EngineeringChalmers University of TechnologyABSTRACTRare earth elements (REEs) have become vital components in a wide range of industrial applications. The demand for the REEs has grown significantly in the last few decades. This has led to increasing costs and supply chain risk. Today, despite lower prices than in 2011, they are classified as the highest supply risk elements in the EU; thus new incentives for recycling the REEs out of electronic scrap were brought forth. End-of-life neodymium magnets are a viable source for the recovery of some REEs. Although mainly iron alloys, these materials contain neodymium, dysprosium and small admixtures of praseodymium and terbium. Leaching followed by solvent extraction of the REEs out of the leachate is an attractive and efficient way of recycling these elements out of end-of-life neodymium magnets. The issues that are encountered along this recycling path is the separation of the REEs from the other elements that are dissolved with the REEs into the leachate and achieving high separation factors between the REEs from each other. Extracting agents such as D2EHPA (di(2-ethylhexyl)phosphoric acid) and TODGA (tetraoctyl diglycolamide) have been previously used for achieving good separation of the REEs under specific extraction conditions.This thesis has focused on the development and optimization of REE extraction from real commercial waste sources, the nitric acid and sulfuric acid media leachates of the neodymium magnet waste, using TODGA and D2EHPA as extracting agents, respectively. Selective REE extraction from the solution with minimal or no co-extraction of other elements in the leachate is hoped to provide a novel route to a commercially viable route to recyclable REE products. The composition of the organic phase was investigated in order to study the effect of the diluent on the overall extraction process, a well-known optimization parameter, however infrequently used. The effect of the diluent on the separation factors was also discussed as well as some characteristics of the aqueous phase on the overall extraction process. The named extractants were used at various concentrations in different diluents like solvent 70, hexane, octane, cyclohexanone, toluene, 1-octanol and chloroform. Both extractants demonstrated good selectivity concerning the extraction of the REEs out of the neodymium magnet waste leachates. KEYWORDS : neodymium magnets, rare earth metals, recycling, solvent extraction, diluents, TODGA, D2EHPA
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| 6. |
- Sögaard, Christian, 1990, et al.
(författare)
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The long term stability of silica nanoparticle gels in waters of different ionic compositions and pH values
- 2018
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 544, s. 127-136
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Tidskriftsartikel (refereegranskat)abstract
- The use of silica nanoparticles for grouting underground tunnels offers an environmentally friendly option compared to organic grouting materials. Silica sols are commercially available and when mixed with an accelerator (salt) they form gels in a predetermined time. While much research has been focused on the practical implementation of silica sols in grouting as well as on the development of physical parameters such as viscosity and strength development, little is known about the long term stability of the resultant silica gels. When placed in rock fractures, parameters such as pH and ionic composition of groundwater may affect the long term stability and functionality of the gels. In this article we use a newly designed test equipment to simulate the behaviour of silica gels when water passes through the gel structure for up to 488 days. The pH and ionic composition of the water is varied to simulate environments that can be experienced by gels used for grouting applications. Results in the form of ionic composition, volume, and pH of leached water were used to evaluate and predict the lifetime of silica gels. The overall results show that several factors such as water flow and the nature of salt, so called accelerator used for gelling have significant effect on the gel life time. Furthermore, it is shown that the accelerator ions leach from the gels; however, the extent to which they are released from the gel depends upon the salt type. From these results we have predicted the lifetime of the 100 mL gels used in our experiments by using a simple numerical model. The predictions show that the total dissolution time for 100 mL gels are up to hundreds of years.
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| 7. |
- Tunsu, Cristian, 1984, et al.
(författare)
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Reclaiming rare earth elements from end-of-life products: A review of the perspectives for urban mining using hydrometallurgical unit operations
- 2015
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Ingår i: Hydrometallurgy. - : Elsevier BV. - 0304-386X. ; 156, s. 239-258
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Tidskriftsartikel (refereegranskat)abstract
- Due to their large variety of applications, their low supply and high demand, the rare earth elements (REEs) are presently viewed as being among the most critical chemical elements. Because of this, their potential recovery from end-of-life waste products has been extensively discussed both in society and in the scientific literature. This concept of recovering elements contained in end-of-life products, known as urban mining, is regarded as an important step in achieving a sustainable, circular society. This review article discusses the perspectives of reclaiming the REEs from various waste streams using hydrometallurgical methods. Three main streams are discussed in detail (phosphor-containing products, NiMH batteries and permanent magnets), touching on the state-of-the-art of material pre-treatment, leaching and separation of REEs and refining. Comparisons with the extraction of REEs from ores are drawn, bringing forth both the advantages and some of the disadvantages of urban mining.
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