Materials Research Innovations, 2010. Vol. 14 (1): pp. 98-101
Abstract: Catalytic denitration of 1-2M nitric acid by formic acid in the presence of a nanocatalyst has been studied and applied to decompose the waste nitric acid in uranyl nitrate raffinate (UNR), generated during purification of uranyl nitrate by solvent extraction with tri-n-butyl phosphate. The reaction was carried out in batch mode at 70 °C using 0.5% Pt/SiO₂ nanocatalyst. The chief function of the catalyst is the fast generation of HNO₂ from nitric acid in order to reach a threshold concentration 5 x 10^-2-10^-1 mol L^-1. The catalyst was prepared by incipient wetness impregnation technique followed by reduction with hydrazine hydrate and sodium borohydride. The catalyst prepared was characterised by scanning electron microscope and transmission electron microscope, and the percentage of Pt loading was measured by inductively couple plasma atomic emission spectroscopy. Kinetics of the denitration reaction has been investigated using waste nitric acid present in UNR. Experiments carried out with and without the catalyst show that in the presence of the catalyst, the percentage of conversion of waste nitric acid to nitrogen is high and the induction period is short. The rate of reaction depends on amount of catalyst per millilitre of solution. The efficiency of the catalyst in denitration of pure nitric acid as well as nitric acid present in UNR to nitrogen has been studied. From kinetic experiment, it is seen that recycled catalyst is less efficient than the pure catalyst.