Effect of structure on extraction behavior of praseodymium with a series of unsymmetrical diglycolamides from hydrochloric acid

Abstract

The extraction behavior of Pr(III) has been investigated using four kinds of unsymmetrical diglycolamide (DGA) extractants having different alkyl chain lengths, namely N,The effect of the alkyl chain of amidic N atoms in DGAs on the extraction ability of Pr(III) is discussed. The extraction of hydrochloric acid and Pr(III) from hydrochloric acid medium by DGAs in sulfonated kerosene, toluene and octanol was studied. The effect of extractant concentration and diluents on the distribution ratio (D) of Pr(III) was investigated to understand the extraction mechanism. Pr(III) and Fe(III) can be separated very well by DMDDdDGA and DBDDdDGA diluted by toluene in hydrochloric acid solution. IR spectra of extracted species of DGA-HCl and DGA-Pr(III) were recorded to study the structure of the extracted species.

Structure Activity Relationship Approach toward the Improved Separation of Rare-Earth Elements Using Diglycolamides

“…Han et al demonstrated that the N , N ′-di­( n -dodecyl) DGAs with smaller N , N ′-alkyl substituents are beneficial to praseodymium­(III) extraction and follow the trend methyl > ethyl > propyl > butyl . We observe the same overall trend in our series of extracting agents 3 , 7 , and 8 ; that is, the extraction strength increases with shortening of the alkyl substituent (Figures c and a).…”

“…Han et al demonstrated that the N,N′-di(n-dodecyl) DGAs with smaller N,N′-alkyl substituents are beneficial to praseodymium(III) extraction and follow the trend methyl > ethyl > propyl > butyl. 36 We observe the same overall trend in our series of extracting agents 3, 7, and 8; that is, the extraction strength increases with shortening of the alkyl substituent (Figures 4c and 5a). Interestingly, this effect is only pronounced in the early lanthanide region (from lanthanum to samarium) because all three extractants show comparable D for europium through lutetium.…”

“…The diglycolamides (DGAs)tridentate oxygen-based complexantsat first developed for actinide/lanthanide partitioning in the nuclear fuel cycle, − are proposed as an effective alternative to acidic extractants to achieve the efficient separation of heavy REEs from light REEs (the reported average adjacent-lanthanide separation factor for light REEs lanthanum–praseodymium in the REE­(III)-HCl-TODGA system is 2.6). Most studies reported so far have looked at the separation of REE(s) by DGAs from nitric acid media, − ,− whereas only a few studies have focused on the separation of REE(s) from hydrochloric acid. − While hydrochloric acid offers cost and environmental advantages for hydrometallurgical REE applications, new questions arise regarding how to control the selectivity and overcome weaker extraction of hydrophilic chloride salts into a nonpolar diluent using neutral extracting agents.…”