Selective Decomposition of Aqueous Nitrate into Nitrogen Using Iron Deposited Bimetals
journal contributionposted on 01.04.2009, 00:00 by Ya Hsuan Liou, Chin Jung Lin, Shih Chi Weng, Hsin Hung Ou, Shang Lien Lo
In the case of the reduction of nitrate in groundwater, the problem is how to convert nitrate [N(+V)] selectively to nontoxic dinitrogen [N(0)] and not to completely reduced ammonia [N(−III)]. Unfortunately, near 100% of the total nitrogen in nitrate is reductively converted to ammonia using naked zerovalent iron (ZVI) thus far reported. In this study, deposition of noble metals (Pt, Pd, and Au) and Cu on iron surface to offer favorable pathways for nitrate reduction was fabricated using either the complete mixing or the successive method with spontaneous redox reactions. The prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy/energy disperse X-ray spectroscopy, and electrochemical analysis. The formation of N2 from the reduction of nitrate was confirmed by residual gas analyzer coupled to a high vacuum system. Based on the experimental results, the ZVI deposited Pd and Cu closely is suggested to promote the abstraction of oxygen from NOx by adsorbed atomic hydrogen on the Cu surface, and enhance N2 formation on the Pd surface. An optimum N2 selectivity of ∼30% obtained in the alkaline solution containing nitrate using 0.3 wt.% Pd-0.5 wt.% Cu/Fe is evident. For groundwater treatment, iron deposited Pd and Cu could facilitate the development of a process requiring neither a massive addition of chemicals nor complex equipment.