Pd/In-based catalysts for nitrate catalytic removal from water: synthesis designs aiming for better N2 selectivity

Abstract

Catalysts based on Pd/In were prepared through the wet impregnation method using Al2O3, SiO2, and TiO2 as supports. The impact of the synthesis procedure on N2 selectivity was studied. Characterization was performed using X-ray fluorescence and scanning electron microscopy–energy dispersive spectroscopy analysis. The catalytic performance of these materials was evaluated for nitrate removal from water in a batch reactor. The order of better nitrate removal was found to be Al2O3>TiO2>SiO2. The selectivity towards N2 was also impacted by the support used, with Al2O3-based catalysts being the most selective and TiO2-based the least due to strong metal–support interaction. The synthesis stages also impacted nitrate removal efficiency and selectivity, with the highest N2 selectivity (94.4% at 90% nitrate conversion) found in catalysts where In was added after Pd and underwent intermediate calcination, reduction and final reduction stages.