• Resources Recycling
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• v.28 no.6
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• pp.9-17
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• 2019

The use of rare metals in increasing along with the growth of the Fourth industrials revolution and new energy industries, and the recycling of rare metals becomes more important as the used of rare metals increase. In this paper, the domestic and international quality standards of tin metal, one of the rare metals, and the performance test of recycled tin were investigated. As a results of the performance test, it was analyzed that there is no difference in performance between the natural and recycled tin.

• Journal of Powder Materials
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• v.30 no.2
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• pp.101-106
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• 2023

Liquid metal extraction (LME), a pyrometallurgical recycling method, is popular owing to its negligible environmental impact. LME mainly targets rare-earth permanent magnets having several rare-earth elements. Mg is used as a solvent metal for LME because of its selective and eminent reactivity with rare-earth elements in magnets. Several studies concerning the formation of Dy-Fe intermetallic compounds and their effects on LME using Mg exist. However, methods for reducing these compounds are unavailable. Fe reacts more strongly with B than with Dy; B addition can be a reducing method for Dy-Fe intermetallic compounds owing to the formation of Fe₂B, which takes Fe from Dy-Fe intermetallic compounds. The FeB alloy is an adequate additive for the decomposition of Fe₂B. To accomplish the former process, Mg must convey B to a permanent magnet during the decomposition of the FeB alloy. Here, the effect of Mg on the transfer of B from FeB to permanent magnet is observed through microstructural and phase analyses. Through microstructural and phase analysis, it is confirmed that FeB is converted to Fe₂B upon B transfer, owing to Mg. Finally, the transfer effect of Mg is confirmed, and the possibility of reducing Dy-Fe intermetallic compounds during LME is suggested.

• Resources Recycling
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• v.27 no.3
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• pp.8-15
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• 2018

Solvent extraction behavior of light rare earth elements (Pr, Nd) and medium rare erath elements (Tb, Dy) in the HCl-PC88A-kerosene extraction system was investigated in order to separate high-purity light rare earths (Pr, Nd) and medium rare earths (Tb, Dy) in the mixed rare earth chloride solution. In the batch test step, it was confirmed that the separation efficiency was good when the extractant concentration (PC88A) was 0.5 M, the equilibrium pH after extraction was 0.8 to 1.0 (initial pH 1.3 of the feed), the concentrations of hydrochloric acid in scrubbing solution was set as 0.1 M, the concentrations of hydrochloric acid in stripping solution was set as 2.0 M or more. Based on the experimental data obtained from the batch test, the mixer-settler was composed as follows; 4 stages of extraction, 8 stages of scrubbing, 4 stages of stripping, and 3 stages of pickling organic solution. The Mixer-settler was operated for 180 hours, and the operating conditions were continuously adjusted to obtain the high-purity light/medium rare earths. Finally, the purity of light (Pr, Nd) and medium rare earth elements (Tb, Dy) was reached as 3 N class.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.440-450
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• 1992

Three type extraction processes of rare earth metal component from rare earth metal bearing ore were sulfuric acid digestion, caustic soda leaching and decomposition with $(NH_4)_2SO_4$. From the overall results, both caustic soda leaching and sulfuric acrid digestion were better extraction processes for domestic monazite ore. The proper conditions of sulfuric acid digestion for domestic monazite ore were reaction temperature $210^{\circ}C$, reaction time 40 min, weight ratio of $H_2SO_4$ to monazite ore 1.5 and concentration of $H_2SO_4$ 95%. Under these conditions, 98% of rare earth metal component was extracted and also the reasonable conditions for caustic soda leaching were reaction temperature $140^{\circ}C$, weight ratio of NaOH to monazite 3.0, concentration of caustic soda solution 50% and leaching time 3hrs. Under these conditions, 97% of rare earth metal component was extracted.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.337-337
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• 2004

As one of researches for the P ＆ T purposes, a basic experiment on the recovery of actinide elements from the mixture with rare earth elements by means of electrorefining using a liquid cadmium cathode in the LiCl-KC1 eutectic melt was carried out. In order to examine the behaviors of electrodeposition of metal ions on a liquid electrode, recovery experiments of rare earth metals resulting from forming electrodeposits were performed by a galvanostatic electrolysis method at various current densities. A cyclic voltammetric technique was applied to determine reduction-oxidation potential of each metal element in the melt and to detect the changes of the multi component melt composition for on-line monitoring. Also, a collaboration study with RIAR was completed to test the preliminary feasibility on a recovery of actinide elements from the mixture with rare earth elements using a liquid cadmium cathode and actinide metals. Experimental results showed that the ratio of actinides to rare earths, 9: 0.5∼1 led to the rare earth content of about 5∼10 wt% in the deposit.

• Journal of Powder Materials
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• v.25 no.2
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• pp.165-169
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• 2018

Rare earth elements (REEs) are considered to be vital to modern industry due to their important roles in applications such as permanent magnets, automobile production, displays, and many more. The imbalance between demand and supply of REEs can be solved by recycling processes. Regarding the needs of industry and society, the International Organization for Standardization, Technical Committee 298 (ISO/TC298) Rare Earths has been recently launched for developing international standards on rare earth elements. In accordance with the suggestion of its constituents, it is tentatively working to develop the appropriate standards under five working groups (WG) on terms and definitions (WG1), element recycling (WG2), environmental stewardship (WG3), packaging, labelling, marking, transport, and storage (WG4), and testing analysis (WG5). The scope and structure of ISO/TC298 on the topic of rare earths is discussed in this document.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.625-630
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• 2005

This study was focused on the catalytic activity for the combustion of low-concentration methane using various commerical catalysts (six transition metal catalysts in Russia and one rare earth metal (Honeycomb) catalyst in Korea). Catalytic activity was strongly influenced by the type and loading content of metal supported in catalyst. Catalytic performance showed the highest activity in Honeycomb catalyst including rare earth metal, which was the most expensive catalyst, while the next was the catalyst supported Cu with high content (AOK-78-52) and also that supported Cr and Co (AOK-78-56). However, both AOK-78-52 and AOK-78-56 catalysts that were very cheap had lower activation energy than Honeycomb catalyst. In the economical field, both AOK-78-52 and AOK-78-56 catalysts with transition metals showed a good alternative catalyst on the combustion of methane.

• Resources Recycling
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• v.30 no.3
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• pp.41-46
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• 2021

Methanesulfonic acid (MSA) can be considered effective in the leaching of metals because of its advantageous physical and chemical properties. The chemical reactivities of MSA and sulfuric acid were compared based on their structures and the dissolution data of Co and Ni metal. The inductive and resonance effects play a vital role in the chemical reactivities of these two acids. The dissolution percentages of Co and Ni in the sulfuric acid solution were higher than those in the MSA solution under the same experimental conditions. Considering the strong acidity of MSA and the high solubility of its metal salts, MSA can be employed as a leaching agent for the recovery of metals.

• Resources Recycling
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• v.30 no.2
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• pp.53-60
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• 2021

Leaching experiments from single metal and metallic mixtures were conducted to develop a process for the recovery of cobalt, copper, and nickel in spent lithium ion batteries. Inorganic and organic acid solutions without oxidizing agents were employed. No copper was dissolved in the absence of an oxidizing agent in the leaching solutions. The leaching condition to completely dissolve single metal of cobalt and nickel was determined based on acid concentration, reaction temperature and time, and pulp density. The leaching condition to dissolve all of cobalt and nickel from the metallic mixtures was also obtained. Leaching of the metallic mixture with methanesulfonic acid led to selective dissolution of cobalt at low temperatures.

• Journal of Powder Materials
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• v.28 no.2
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• pp.91-96
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• 2021

Rare earth magnets with excellent magnetic properties are indispensable in the electric device, wind turbine, and e-mobility industries. The demand for the development of eco-friendly recycling techniques has increased to realize sustainable green technology, and the supply of rare earth resources, which are critical for the production of permanent magnets, are limited. Liquid metal extraction (LME), which is a type of pyrometallurgical recycling, is known to selectively extract the metal forms of rare earth elements. Although several studies have been carried out on the formation of intermetallic compounds and oxides, the effect of oxide formation on the extraction efficiency in the LME process remains unknown. In this study, microstructural and phase analyses are conducted to confirm the oxidation behavior of magnets pulverized by a jaw crusher. The LME process is performed with pulverized scrap, and extraction percentages are calculated to confirm the effect of the oxide phases on the extraction of Dy during the reaction. During the L ME process, Nd is completely extracted after 6 h, while Dy remains as Dy₂Fe₁₇ and Dy-oxide. Because the decomposition rate of Dy₂Fe₁₇ is faster than the reduction rate of Dy-oxide, the importance of controlling Dy-oxide on Dy extraction is confirmed.