Mono and bimetallic NaY catalysts with high performance in nitrate reduction in water

Abstract

The catalytic reduction of nitrate in water was performed with mono and bimetallic catalysts based on NaY zeolite. Four catalysts, two monometallic (Cu-Y and Pd-Y) and two bimetallic (CuPd-Y and PdCu-Y) were prepared by the ion-exchange method using the faujasite zeolite in the sodium form (NaY, 700 nm). The contents of promoter and noble metals were kept in the range of 0.60-0.84 wt% for copper and 0.92-1.80 wt% for palladium. Characterization by several methods: spectroscopic techniques (FTIR, XRD), chemical analysis, nitrogen adsorption, scanning electron microscopy (SEM), temperature programmed reduction (TPR) and cyclic voltammetric, demonstrated that ion exchange of the metals into NaY zeolite was successful. The catalytic behavior of the catalysts was evaluated in a semi-batch reactor, working at room temperature and pressure. The best catalyst was obtained with the pair copper and palladium (0.64 wt% of Cu and 1.80 wt% of Pd), which allowed 100% nitrate conversion with selectivities to nitrogen as high as 94% under the conditions tested.