Catalytic hydrogenation of Cl-oxyanion pollutants in water

Abstract

Pt and Pd catalysts supported on alumina have been tested and characterised for the catalytic hydrogenation of chlorates at room temperature and atmospheric pressure. Metallic nanoparticles are the catalytic active species, obtaining better results with the Pt than with the Pd catalysts. It is observed that the activity of the Pt catalysts depends on the metal precursor used for their preparation and the calcination temperature as these factors lead to different platinum dispersion on the alumina surface. The best results were obtained with the catalysts prepared from metal precursors containing Cl atoms and calcined at lower temperatures, as smaller metallic crystallites are formed. The chlorate reduction profiles displayed a pseudo-first order kinetic towards chlorate. The optimised catalyst was tested for the reduction of the different Cl-oxyanions, proving that the reaction rate depends on the chlorine valence of the ion following this order: ClO4- < ClO3- < ClO2-. This is due to the different molecular geometry of the anions that results in different stability of the ClOx-. The optimised catalyst was fully stable in successive uses, being active for the simultaneous reduction of chlorate, chlorite and bromate in water.