Novel Extraction Process Of Rare Earth Elements From NdFeB Powders Via Alkaline Treatment

Abstract

The alkaline treatment of NdFeB powders in NaOH solution at various equivalent amounts of NaOH at 100• C was performed. The resultant powders were then leached in 0.5M H 2 SO 4 solution at 25• C for 2 minutes. At 5 equivalents of NaOH, neodymium in NdFeB powders was partially transformed to neodymium hydroxide. The transformation of neodymium to neodymium hydroxide actually occurred at 10 equivalents of NaOH and was facilitated by increasing the equivalent of NaOH from 10 to 30. In addition, iron was partially transformed to magnetite during the alkaline treatment, which was also promoted at a higher equivalent of NaOH. The leaching yield of neodymium from alkaline-treated powders was increased with an increasing equivalent of NaOH up to 10; however, it slightly decreased with the equivalent NaOH of over 10. The leaching yield of iron was inversely proportional to that of rare earth elements. NdFeB powders treated at 10 equivalents of NaOH showed a maximum leaching yield of neodymium and dysprosium of 91.6% and 94.6%, respectively, and the lowest leaching yield of iron of 24.2%, resulting in the highest selective leaching efficiency of 69.4%.

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

“…Leaching of the magnets or magnets scrap (acidic or alkaline treatment), followed by separation of REEs using solvent extraction, ion exchange technology or selective precipitation [5,6,[15][16][17][18][19] Ionometallurgy Use of ionic liquids in the liquid-liquid extraction of REEs present in NdFeB magnets [20][21][22][23][24][25] Electrochemical leaching Electrochemical leaching of REEs is achieved at lower cell voltages by adding oxalic acid in the sulfuric acid leach solution. Separation of REEs is achieved by precipitation using H 2 C 2 O 4 [26] Acid baking with water leaching and ultrasonic spray pyrolysis Magnets are crushed, grinded and sieved.…”

An Overview on Resource and Recovery Prospectives of the Critical Element Neodymium

“…Under the optimum leaching conditions; Time = 180 min, temperature = 90 °C, [CH 3 COOH] = 1 kmol m -3 , agitation speed = 400 rpm and 1 % leaching pulp density around 94.2 % Nd, 93.1 Dy, and 1 % Fe were leached [61]. Chung et al [62] have designed a new process in which NaOH acted as a catalyst and the leaching was performed with 0.5 M H 2 SO 4 which exhibited poor selectivity for Fe. On increasing equivalent of NaOH up to 10, the leaching efficiency of Nd from alkaline treated powders was found to increase.…”

“…On increasing equivalent of NaOH up to 10, the leaching efficiency of Nd from alkaline treated powders was found to increase. Under this condition highest leaching of 91.6 % Nd and 94.6 % Dy and the lowest yield of 24.2 % Fe have been observed [62]. Schulze et al [63] have conducted ex-ante LCA analysis on the REE recovery from NdFeB magnet using the molten fluoride electrolysis method so that early assessment of new technologies would help to scale from laboratory experiment levels to pilot scale.…”

Hydrometallurgical recycling strategies for recovery of rare earth elements from consumer electronic scraps: a review

“…89 To eliminate the hazardous effects of inorganic acids, acetic acid was investigated as a green leaching process for Nd extraction from NdFeB magnet scrap: 90 from a scrap containing 31.05% Nd and 65.15% Fe, 99.99% Nd was extracted at 10 g L −1 pulp density (PD), 80°C using 0.4 mol L -1 acetic acid and 106-150 μm particles. An alkaline treatment was evaluated by Chung et al 91 where NdFeB powders induced transformation of Nd and Fe to Nd(OH) 3 and magnetite, respectively, in NaOH solution at 100°C for 5 h. The treated powder was further treated in a solution of 0.5 mol L -1 H₂SO₄ at 25°C for 2 min. When NdFeB powders were treated at 10 equivalents of NaOH, 91.6% Nd and 94.6% Dy were extracted with <25% Fe.…”