HETEROPOLY COMPOUNDS AS SOLID-PHASE CATALYSTS IN THE PROCESSES OF ACTINIDE ION REDUCTION WITH HYDRAZINE IN HNO3 SOLUTIONS

Addition of a catalyst, a heteropoly compound (HPC) of the 12th series , in a hydrazine-containing Pu(IV) or Np(V) solution sharply accelerat es reduction of these actinides to Pu(III) and Np(IV), respectively. T hese reactions are irreversible first-order processes. The reaction co nstant increases linearly as the ratio between the weight of the solid phase and the volume of the liquid phase increases. With increasing t he HPC amount on the support the reaction rate increases. Cs5PV2Mo10O4 0 supported on silica gel was found to be the best catalyst. The activ ation energy of reduction of Pu(IV) to Pu(III) is about 80 kJ mole(-1) . The mechanism of catalytic reactions in the presence of HPC is suppo sed to consist in the accumulation of heteropoly blues in the reaction medium under the action of the reducing agent. The heteropoly blue im mediately reduces actinide ions.