| Summary: | The catalytic removal of nitrate (NO<sub>3</sub><sup>−</sup>) in water using hydrogen as a reducing agent was studied using palladium-copper bimetallic catalysts in different supports. Commercial carbon nanotubes (CNTs), used as received and with different mechanical (CNT (BM 2h)) and chemical modifications (CNT (BM 4h)-N), titanium dioxide (TiO<sub>2</sub>) and composite materials (TiO<sub>2</sub>-CNT) were considered as main supports for the metallic phase. Different metal loadings were studied to synthesize an optimized catalyst with high NO<sub>3</sub><sup>−</sup> conversion rate and considerable selectivity for N<sub>2</sub> formation. Among all the studied support materials, the milled carbon nanotubes (sample CNT (BM 2h) was the support that showed the most promising results using 1%Pd-1%Cu as metallic phases. The most active catalysts were 2.5%Pd-2.5%Cu and 5%Pd-2.5%Cu supported on CNT (BM 2h), achieving total conversion after a 120 min reaction with N<sub>2</sub> selectivity values of 62% and 60%, respectively. Reutilization experiments allowed us to conclude that these catalysts were stable during several reactions, in terms of NO<sub>3</sub><sup>−</sup> conversion rate. However, the consecutive reuse of the catalyst leads to major changes concerning NH<sub>4</sub><sup>+</sup> selectivity values.
|
|---|