Catalytic Hydrogenation of Nitrate in Water Using a Pd–Cu/Al2O3 Catalyst and Dilute H2 Microbubbles

The catalytic hydrogenation of nitrate was per- formed in solutions containing 20 mg/dm 3 NOusing a Pd- Cu/Al2O3 catalyst (synthesized with a Cu/Pd ratio of 0.25) together with microbubbles (radii\50 lm) of 9.4-43.7 % H2 in N2. Significant enhancement of the hydrogenation rate was observed due to the application of the microbubbles. The nitrate conversion factors for microbubble hydrogenation were approximately 1.7-3.8 times greater than those obtained using conventional macrobubbles (radii (1500 lm). The application of microbubbles was also effective during hydro- genation in a more concentrated nitrate solution containing 77 mg/dm 3 NO � . Graphical Abstract