Nitrate Catalytic Reduction over Bimetallic Catalysts: Catalyst Optimization

• Published in: C (Basel) Vol. 6; no. 4; p. 78
• Main Authors: Santos, A. Sofia G. G., Restivo, João, Orge, Carla A., Pereira, M. Fernando R., Soares, O. Salomé G. P.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-12-2020
• Subjects: Adsorption; bimetallic catalysts; Bimetals; Carbon; Carbon nanotubes; Catalysts; catalytic reduction; Chemical reduction; Chemical synthesis; Composite materials; Conversion; Copper; Drinking water; Efficiency; Metals; Nitrate removal; Nitrates; Nitrogen; Optimization; Palladium; Reducing agents; Selectivity; Titanium; Titanium dioxide; Water treatment
• ISSN: 2311-5629; 2311-5629
• DOI: 10.3390/c6040078

The catalytic removal of nitrate (NO3−) 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 (TiO2) and composite materials (TiO2-CNT) were considered as main supports for the metallic phase. Different metal loadings were studied to synthesize an optimized catalyst with high NO3− conversion rate and considerable selectivity for N2 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 N2 selectivity values of 62% and 60%, respectively. Reutilization experiments allowed us to conclude that these catalysts were stable during several reactions, in terms of NO3− conversion rate. However, the consecutive reuse of the catalyst leads to major changes concerning NH4+ selectivity values.