Solvent extraction of rare earth metals with crown ethers

Abstract

117, Republic of ChinaCrown ethers, such as 15-crown-5, 12-crown-4 and dibenzo-18-crown-6, were used to extract individual rare earth ions from aqueous solutions containing picrate into nitrobenzene solution. The rare earth metal ion europium(II1) is extracted as a 2 : 1 crownion sandwich complex with 12-crown-4, but as a 1 : 1 complex with both 15-crown-5 and dibenzo-18-crown-6. From studies of picric acid concentration effects on complexation, the extracted species of Eu (NO,), with 15-crown-5 and dibenzo-18-crown-6 are E u [ ( 15-crown-5)-(picrate),(NO,)] and Eu[(dibenzo-l8-crown-6) (picrate) ,(NO,)], respectively, but Eu[( 12-crown-4), (picrate),] is formed with 12-crown-4. The extraction of rare earth ions showed that Tb3+, Eu3+, Gd3+, Nd3+ and Yb3+ can be easily extracted using 15-crown-5; however, the extraction of Ce4+, Sm3+, Dy3+ and Lu3+ is more difficult. Keywords Rare earth metals ; solvent extraction; crown ethers I II 111 Experimental ReagentsCrown ethers, 15crown-5 and 12-crown-4, were obtained from E. Merck. Dibenzo-18-crown-6 was synthesised All reagents except the following were of analytical-reagent grade.

Complexation of Americium(III) with Crown Ethers in Aqueous Phase

“…action of U(VI) with crown ethers has been reported [20]. The present studies suggest that attempts made by earlier workers [17,21,22] to correlate the extraction behaviour of trivalent lanthanide ions in analogous systems with their crystal ionic radii are not justified. There is no particular reason to invoke crystal ionic radii in order to explain the trends in distribution coefficients, even for other extraction systems involving actinide ions and crown ethers [23,24].…”

Application of the Bifunctional Switch-Type Cryptand Ion Chromatographic Stationary Phase for Ion Separation

“…Artificial macrocyclic polyethers such as crown ethers and cryptands have demonstrated a remarkable ability to complex various metal ions (1)(2)(3)(4)(5)(6), and their applications in the separation and analysis of metal ions have been extensively studied (7)(8)(9)(10)(11). Owing to their high selectivity in forming complexes with metal ions, crown ethers and cryptands are expected to be suitable column materials in ion chromatography for the separation of metal ions.…”

pH-Controlled Selective Separation of Neodymium (III) and Samarium (III) from Transition Metals with Carboxyl-Functionalized Ionic Liquids

“…From the viewpoint of sustainable development, the key to solving supply problems is the recovery of Nd and Sm from waste rare-earth materials. , It is known that NdFeB magnet contains about 59 wt % Fe and 26 wt % Nd, and a SmCo magnet consists of about 76 wt % Co and 24 wt % Sm. , Thus, it is important to recover Nd and Sm from NdFeB and SmCo magnets, respectively. As far as the separation techniques are concerned, liquid–liquid extraction is always found to be a simple and effective way for the separation of rare-earth metal from common metals. − However, in the conventional liquid–liquid extraction, water-immiscible organic solvents are often used as diluents, which are usually flammable, volatile, and hazardous to the environment. Therefore, development of sustainable and efficient techniques is greatly necessary for the separation of the neodymium and samarium from transition metals such as iron and cobalt.…”