Extraction of rare earth elements with 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate impregnated resins having different morphology and reagent content

Extraction of rare earth elements (REEs) with reagent impregnated resins (RIRs) using 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (PC-88A) and Amberlite XAD-2, XAD-4, XAD-16 and XAD-7 as a polymeric support has been studied. The impregnated resins containing various amounts of PC-88A have been prepared by a dry method. The effect of contact time on the extraction of REEs with PC-88A impregnated resins (PC-88A-resin = 20/80, 50/50 wt.%) at pH 3.5 has been chiefly investigated. It was found that the extraction becomes slow when an insufficient amount of PC-88A was impregnated into XAD-2, XAD-4 or XAD-16 resins with respect to their pore volume. Little effect of the amount of PC-88A in XAD-7 on the rate of extraction was observed. The presence of n-dodecane improves the extraction kinetics for XAD-4 and XAD-16 at a small PC-88A content. It is speculated that PC-88A should be filled in the pore of the resin from the bottom to the top under the present impregnation process. It is thus recommended to make RIRs with enough of the reagent to fill up the pores of hydrophobic resins in this impregnation method. (C) 2001 Elsevier Science BY All rights reserved.