Elimination of NO3 - from water using Pd and PdCu catalysis supported on ZrO2–CeO2 materials: Effect of the support preparation

Abstract

The catalytic reduction of NO3− in synthetic and real water samples was studied using Pd and PdCu catalysts supported on pure CeO2 and CeO2 modified with 5 wt%. ZrO2. The supports were prepared by both calcination and sol-gel methods to study the effect of the preparation on the catalytic performance. The prepared catalysts were characterized by different techniques, including N2 physisorption, SEM-EDS, XRD, XPS, and TPR. Monometallic Pd catalysts were active in NO3− elimination, and the addition of Cu generated new active sites. The catalysts synthesized by calcination presented lower NO3− removal capacity compared to those prepared by sol-gel, due to their lower surface area and porosity. Oxygen vacancies (Ce+4/Ce+3 couple) were verified in the supports prepared by sol-gel by XPS. These vacancies were more evident in the materials modified with ZrO2. All the catalysts evaluated presented good selectivity (above 90%) to N2, the innocuous and desired product. The PdCu/ZCBSG catalyst showed the highest activity, due to the better dispersion of ZrO2 on CeO2 on the support, corroborated by XRD and EDS analysis. Besides, this catalyst was evaluated in the NO3− reduction in real water samples, extracted from the Puelche Aquifer, in Buenos Aires, Argentina.