Characterization and catalytic performance of a bimetallic Pt–Sn/HZSM-5 catalyst used in denitratation of drinking water

Removal of nitrates and nitrites from drinking water by catalytic hydrogenation over zeolite-supported Pt–Sn catalysts was studied. Bimetallic Pt–Sn/HZSM-5 catalysts were characterized by temperature-programmed reduction (TPR), H2 chemisorption, X-ray photoelectron spectroscopy (XPS) and 119Sn Mössbauer spectroscopy. The characterization techniques showed a significant decrease in the H/Pt ratio upon tin addition, tin surface enrichment, the formation of PtSn alloys and platinum catalysis of the tin reduction. The Pt–Sn/HZSM-5 catalyst clearly showed high catalytic activity for the reduction of nitrate to form N2. In the bimetallic catalyst, the role of tin is to reduce nitrate or nitrite according to a redox process, while the platinum maintains tin in the metallic state.