Equilibrium and kinetic studies of the reductive stripping of uranium from DEPA-YOPO reagent into aqueous phosphoric acid

Abstract

As of mid-1983, over 1000 tons of U 3O 8 per year is being recovered in the U.S.A. from wet-process phosphoric acid using the DEPA-TOPO process developed at Oak Ridge National Laboratory. Another 3000 tons of U 3O 8 per year passes through a number of small phosphate plants unrecovered, because the economics of the process are considered to be marginal at current market conditions. This paper describes equilibrium measurements, studies of uranium reduction kinetics, and uranium(IV) extraction which show how the efficiency of the reductive strip step, a key process operation, can be significantly increased by the use of higher concentrations of H 3PO 4 in the aqueous strip solution. This procedure greatly improves the reduction kinetics allowing decreased retention time in the mixers, use of lower Fe(II) concentration, and smaller process equipment. A model of a mixer-settler unit describes the system over a 5–10 molar H 3PO 4 range.