Effect of pKa of organophosphorus acidic extractants on the aggregation behavior of diglycolamide in n-dodecane

To understand the role of pKa of the organophsophorus acidic extractant on the reverse micellar aggregation behavior of the binary solution containing tetra-(2-ethylhexyl)diglycolamide (TEHDGA) + acidic extractant in n-dodecane, the extraction behavior of nitric acid and Nd(III) in the binary solution was studied. The acidic extractants chosen were bis(2,4,4-trimeth-ylpentyl)phosphinic acid (CYANEX-272), bis(2-ethylhexyl)phosphonic acid (PC88A) and bis(2-ethylhexyl)phosphoric acid (HDEHP). The results revealed that the acidic extractant with lower pKa produced aggregates of smaller size, and therefore, the binary solution containing TEHDGA and HDEHP in n-DD was identified as the promising solvent for the extraction of trivalent metal ions from nuclear waste. (author)