Noble Metal-Catalyzed Ammonia Generation by Formic Acid Reduction of Nitrate in Simulated Nuclear Waste Media

Simulants for the Hanford Waste Vitrification Plant (HWVP) feed containing the major non-radioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO3 2-, NO3 -, and NO2 - were used to study the formic acid reduction of nitrate and/or nitrite to ammonia at 90 °C catalyzed by the noble metals Ru, Rh...

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Bibliographic Details
Published in:Environmental science & technology 1997-04, Vol.31 (4), p.984-992
Main Authors: King, R. B, Bhattacharyya, N. K, Smith, H. D, Wiemers, K. D
Format: Article
Language:English
Subjects:
Acids
Ammonia
Applied sciences
Chemicals
Exact sciences and technology
Pollution
Radioactive wastes
Wastes
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Summary:Simulants for the Hanford Waste Vitrification Plant (HWVP) feed containing the major non-radioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO3 2-, NO3 -, and NO2 - were used to study the formic acid reduction of nitrate and/or nitrite to ammonia at 90 °C catalyzed by the noble metals Ru, Rh, and/or Pd found as fission products in waste from the reprocessing of irradiated uranium. Reactions of this type were monitored using gas chromatography to analyze the CO2, H2, NO, and N2O in the gas phase and a microam monia electrode to analyze the NH4 +/NH3 in the liquid phase as a function of time. The rhodium-catalyzed reduction of nitrogen−oxygen compounds to ammonia by formic acid was found to exhibit the following features:  (1) Nitrate rather than nitrite is the principal source of ammonia. (2) Ammonia production occurs at the expense of hydrogen production. (3) Supported rhodium metal catalysts are more active than rhodium in any other form, suggesting that ammonia production involves heterogeneous rather than homogeneous catalysis.
ISSN:0013-936X
1520-5851
DOI:10.1021/es960335+