Recovery of uranium phosphate by a stepwise thermal treatment of uranium-bearing spent TBP

Abstract

A stepwise thermal treatment process for the recovery of uranium phosphate from uranium-dissolved spent TBP was demonstrated. The pathway of the reactions involved in the thermal decomposition and oxidation processes of uranium-bearing spent TBP was established based on the results of thermogravimetric analyses. Relatively low-temperature pyrolysis is required to avoid the condensation of corrosive phosphoric acid via vaporization. Low-temperature pyrolysis residue was analyzed and found to be composed of pyrocarbon, phosphorus oxide (P 2 O 5 ) and two types of uranium phosphate (UP 2 O 7 and UP 4 O 12 ). Uranium pyrophosphate (UP 2 O 7 ) was recovered from the burning out of pyrocarbon in the pyrolysis residue after the dissolution removal of phosphorus oxide in water. A substantial recovery of uranium by the proposed stepwise thermal treatment method was successfully demonstrated by a treatment of pyrolysis residue from a benchscale low-temperature pyrolysis process.