Simultaneous recovery and separation of uranium and rare earths from phosphoric acid in a one-cycle extraction-stripping process

Abstract

A new technology for uranium and rare earth recovery from wet process phosphoric acid (WPA) in a one-cycle extraction-stripping method was simple and easy to control because only acidic media were involved. The process is based on uranium and rare earth extraction from WPA with di(2-ethylhexyl)phosphoric acid (DEPA) and tri-n-butylphosphate (TBP). DEPA was found to be the only efficient, stable and easy to strip extractant. Other organophosphoric (acidic) esters are unstable against hydrolysis and are difficult to strip. The stripping process is carried out with a medium containing acidic fluoride for both rare earths and for uranium. In the latter case uranium extracted as U(VI) is reduced to U(IV) inextractable state by Fe(II) introduced into the stripping solution. Both rare earths and uranium as U(IV) are instantly precipitated as fluorides. Uranium precipitates as UF 42.5H 2O or a tetravalent compound, depending on the stripping solution. The precipitate is a “green cake”. The “green cake”, with previous dehydration in nitrogen atmosphere at 400°C, could be oxidized by F 2 to hexafluoride, UF 6, of high purity. The rare earth fraction consisted of the yttrium group, with yttrium as the predominant element. The process described here requires lower investment costs than those of a dual extraction-stripping process. Operation costs involved are approximately US $ 30/kg for green WPA.