Extraction of uranium(VI) from dilute phosphate solutions with neotridecanohydroxamic acid and amines

Abstract

Extraction of U(IV) with neotridecanohydroxamic acid (HX-70) depends primarily on the diluent used as well as on the hydrogen, phosphate and hydroxamate ion concentrations. Of the diluents tested, the low-polarity solvent, Shellsol T, gave the best results. The extraction coefficient of U(VI) increases with decrease of phosphate and/or hydrogen ion concentration and is appreciable only at pH values > 2. This limits the applicability of the method to solutions of very low U(VI) concentration. Solutions of higher U(VI) concentration can be treated with amines. The extraction of U(VI) with amines has been investigated using either Primine JMT or Alamine 336 in Shellsol T diluent. Extraction is better with the primary amine, Primene JMT, rather than the tertiary amine, Alamine 336. With Primene JMT, the extraction coefficient of U(VI) is much greater than that of phosphate ions and the difference between the two values increases markedly with increasing pH. This difference can be used for partial separation of U(VI) from phosphate ions. Neotridecanohydroxamic acid affects antagonistically the extraction of U(VI) with amines, but the addition of HX-70 to Primine JMT at a concentration below that which affects extraction may be beneficial since it can lead to a better separation of U(VI) from phosphate ions during the stripping process.