A Comprehensive Extraction Study Using a Mono-alkylated Diglycolamic Acid Extractant: Comparison Between a Secondary Amide Group and a Tertiary Amide Group

Abstract

The extraction characteristics of N-dodecyldiglycolamic acid (C 12 DGAA), with a secondary amide group, for 56 metal ions have been investigated, and compared with those of N,N-dioctyldiglycolamic acid (DODGAA) with a tertiary amide group. C 12 DGAA is capable of quantitative transfer for a variety of metal ions through a proton-exchange reaction, and the extraction behavior as a function of the aqueous-phase pH is similar for C 12 DGAA and DODGAA. Compared with DODGAA, C 12 DGAA has a poor extraction performance and separation ability for rare-earth metal ions, except for Sc(III). However, C 12 DGAA tended to provide better extraction for relatively small-sized metal ions than DODGAA. In addition, it was found that C 12 DGAA enables the selective removal of Hg(II) from aqueous solutions containing various divalent metal ions (Hg(II), Pb(II), Cu(II), Cd(II), Zn(II), Mn(II), Co(II), and Ni(II)).

Rapid and selective recovery of palladium from platinum group metals and base metals using a thioamide-modified calix[4]arene extractant in environmentally friendly hydrocarbon fluids

“…Specifically, in the case of amide groups, the donor oxygen atom acts as a hard base and, according to HSAB theory, will not bind well to the softly acidic Pd(II). Similar results have been reported previously for Pd(II) extraction 31 – 33 . Hence, all further Pd(II) extraction experiments were conducted with extractant 1 only.…”