Novel N,N-dialkylamide carboxylic acids extractants for efficiently selective removal of aluminum to obtain high-purity gadolinium

Novel N,N-dialkylamide carboxylic acids extractants (DOOBA and DOMOPA) were prepared. • The Al(III) impurity was effectively removed from Gd(III) by DOOBA and DOMOPA. • The stability and recycling performance of DOOBA and DOMOPA were proved well. • A high purity Gd 2 O 3 (99.97%) was obtained after a three-stage extraction with DOOBA. The separation of rare earths (REs) and aluminum (Al) is a critical challenging step in REs metallurgy due to their similar chemical properties. This study developed two novel N,N-dialkylamide carboxylic acid extractants-(4-(dioctylamino)-4-oxobutanoic acid (DOOBA), 5-(dioctylamino)-3-methyl-5-oxopentanoic acid (DOMOPA), to separate Al(III) from GdCl 3 solution. Using n-heptane as the diluent, the extraction performances of the DOOBA and DOMOPA systems for separation of Al(III) and Gd(III) were systemically investigated. The results indicated that DOOBA and DOMOPA exhibited effective extraction for Al(III) and low competitive behavior with Gd(III). A further understanding on the thermodynamics extraction mechanism of DOOBA and DOMOPA for Al(III) was discussed. Stripping and recycling performance of the DOOBA and DOMOPA systems were proved well. A three-stage counter-current extraction simulation was carried out to remove Al(III) from industrial GdCl 3 feed. The simulated solutions were employed in this study to elucidate fundamental separation behavior; the research ultimately targets the removal of aluminum impurities from industrial GdCl₃ feeds, which commonly contain impurities such as Al, Fe, and other metal ions. Gd(III) was purified and recovered by oxalic acid precipitation and a subsequent calcination step. Gd 2 O 3 with a purity of 99.97% was obtained. This work provides a new strategy for selective removal of aluminum from GdCl 3 solution to obtain high-purity gadolinium. Download: Download high-res image (119KB) Download: Download full-size image