Catalytic reduction of nitrate in water: Promoted palladium catalysts supported in resin

Nitrate can be eliminated from drinking water by catalytic reduction. Nevertheless, the development of active and selective catalysts for this reaction has not been easy. We found that depending upon the preparation procedure very different catalytic behavior was found, as shown in the figure. The retention capacity of nitrate by ion exchange as well as its conversion depends not only on the metal content, but also in the preparation procedure. The reactive properties of Pd–Cu and Pd–In catalysts over weak anionic exchange resin as support was investigated in the catalytic nitrate reduction. Pd–Cu/resin catalysts were prepared upon different copper fixation procedures (ion exchange method and controlled surface reaction). The samples were tested in a batch reactor with H 2 bubbling and constant pH. The fresh and reacted catalysts were characterized by TEM, EPMA, XRD and XPS. The results demonstrated a higher activity of the Pd–Cu/resin catalyst prepared upon controlled surface reaction due to a high concentration of binary sites in the external surface. On the other hand, the XRD and TEM analyses indicated that sinterization occurs during reaction, leading to an increase in the average particle size. In the same way, a Pd–In/resin was investigated showing more activity and less selectivity than the Pd–Cu/resin sample.