Catalytic reduction of U(VI) with hydrazine using Pt/SiO2 catalyst in nitric acid medium—kinetics and equilibrium

Optimization of Process Variables for the Catalytic Reduction of U(VI) over Pt/SiO2 using Hydrazine as Reducing Agent – Design of Experiments Approach

“…Similarly, the minimal dependency of catalyst loading on the reduction of U(VI) could be due to the excess amount of catalyst employed in the present study such that the surface of the catalyst is always occupied by the reactant molecules under the present experimental conditions. The similar behavior was observed in our previous study confirms the less dependency of U(VI) reduction with N 2 H 4 over Pt/SiO 2 on mixing speed, and catalyst loading [32] . In view of these observations, the mixing speed and the catalyst loading were fixed at the middle level (0) for further studies, and the response surface methodology was employed to optimize the process with significant variables, namely temperature, concentrations of uranium, HNO 3, and N 2 H 4.…”

“…The other parameters such as mixing speed, catalyst loading and temperature were chosen based on our previous experimental studies and literature reported values [28,32] . The total number of experiments (N) required in DSD can be determined using equations (3) & 4 [38] …”

“…It can be seen that the increase of temperature increases the reduction of U(VI) linearly in the lower temperature region followed by saturation in the reduction of U(VI) at higher temperature. Previously we studied the reduction behavior of U(VI) as a function of temperature [28,32] . It was reported that the rate of U(VI) reduction increased with increase of temperature in the lower temperature region followed by a marginal variation in the kinetics of reduction at higher temperature.…”

“…The effect of various process conditions on the reduction of U(VI) using Pt/SiO 2 catalyst was also reported and the authors demonstrated the reaction in a pilot plant scale. Recently, we have investigated intrinsic kinetics of U(VI) reduction in the presence of H 2 and N 2 H 4 over Pt/SiO 2 catalyst in nitric acid medium and derived various kinetic model equation based on Langmuir‐Hinshelwood approach and validated them experimentally [31,32] . All the above studies reported in the literature so far, focused on either understanding the kinetics of the reaction, evaluation of the catalyst material performance, or studying the effect of process variables, one variable at a time approach (OVAT).…”

Hydrazide and amidoxime dual functional membranes for uranium extraction from seawater

“…have been reported to reduce uranium from U( vi ) to lower valence states of U( iv ). 23 In addition to these, some photocatalysts, such as TiO 2 , g-C 3 N 4 and MoS 2 , as well as their composites, have been explored for U( vi ) reduction. Liang et al 24 prepared ZnFe 2 O 4 rods with good stability, recyclability, and magnetic separability as catalysts for visible-light-driven U( vi ) photoreduction.…”