On the catalytic effect of Pd(s) on the reduction of with H2 in aqueous solution

The catalytic effect of Pd(s) (as a model for noble metal particles) on the reduction of UO 2 2 + by H2 has been studied experimentally. The experiments were performed in aqueous solution in an autoclave. The aqueous solutions were pressurized with H2 or N2 and the UO 2 2 + concentration was measured as a function of time. The experiments clearly show that Pd catalyzes the reaction between UO 2 2 + and H2. The rate constant of the reaction was found to be close to diffusion controlled and independent of the H2 pressure in the range 1.5–40 bar. The effect of a catalyzed reduction of U(VI) to U(IV) in the solid phase is also discussed.