Photocatalytic oxidation of aqueous ammonia over platinized microwave-assisted titanate nanotubes
Resource
APPLIED CATALYSIS B-ENVIRONMENTAL, 99(1-2), 74-80
Journal
Applied Catalysis B Environmental
Pages
74-80
Date Issued
2010
Date
2010
Author(s)
Abstract
Batch experiments were conducted to study the photocatalytic oxidation of aqueous ammonia (NH3/NH4+) over platinized titanate nanotubes (platinized TNTs). The reaction kinetics of NH3/NH4+ oxidation is considerably enhanced by the platinization of TNTs. The observed rate constant (kobs) for NH3/NH4+ oxidation over platinized TNTs was 1.69×10-2min-1, while the unamended TNTs gave a kobs=1.23×10-3min-1. The selectivity of nitrogen gas (N2) from degraded NH3/NH4+ increased with platinum loading to 87.8% after 1h photocatalysis. In contrast, NH3/NH4+ to nitrate (NO3-) conversion was low due to a large NH3/NH4+ to nitrite (NO2-) energy barrier. High-resolution transmission electron microscopy shows that platinum deposits are formed primarily on the internal surface of the hollow structure of TNTs instead of being deposited on the external surface of TNTs. Based on the analysis of X-ray photoelectron spectroscopy, a mechanism is proposed in which N2 is produced from the NH3/NH4+ adsorbed on platinum deposits while NO2-/NO3- is formed from the NH3/NH4+ adsorbed on titanate sites. © 2010 Elsevier B.V.
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