Volume 24 (2017) Issue 2 Pages 61-69
The extraction characteristics of N-dodecyldiglycolamic acid (C12DGAA), 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. C12DGAA 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 C12DGAA and DODGAA. Compared with DODGAA, C12DGAA has a poor extraction performance and separation ability for rare-earth metal ions, except for Sc(III). However, C12DGAA tended to provide better extraction for relatively small-sized metal ions than DODGAA. In addition, it was found that C12DGAA 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)).