Electrochemical Oxidation of N-Nitrosodimethylamine with Boron-doped Diamond Film Electrodes

This research investigated NDMA oxidation by boron-doped diamond (BDD) film electrodes. Oxidation rates were measured as a function of electrode potential, current density, and temperature using rotating disk and flow-through reactors. Final NDMA reaction products were carbon dioxide, ammonium, and...

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Bibliographic Details
Published in:Environmental science & technology 2009-11, Vol.43 (21), p.8302-8307
Main Authors: Chaplin, Brian P, Schrader, Glenn, Farrell, James
Format: Article
Language:English
Subjects:
Applied sciences
Boron
Boron - chemistry
Chemical reactions
Diamond - chemistry
Diamonds
Dimethylnitrosamine - chemistry
Dimethylnitrosamine - isolation & purification
Electricity
Electrochemical Techniques
Electrodes
Electron transfer
Exact sciences and technology
Kinetics
Models, Chemical
Oxidation
Oxidation-Reduction
Pollution
Remediation and Control Technologies
Thermodynamics
Time Factors
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Summary:This research investigated NDMA oxidation by boron-doped diamond (BDD) film electrodes. Oxidation rates were measured as a function of electrode potential, current density, and temperature using rotating disk and flow-through reactors. Final NDMA reaction products were carbon dioxide, ammonium, and nitrate, with dimethylamine and methylamine as intermediate products. Reaction rates were first-order with respect to NDMA concentration and surface area normalized oxidation rates as high as 850 ± 50 L/m2-hr were observed at a current density of 10 mA/cm2. The flow-through reactor yielded mass transfer limited reaction rates that were first-order in NDMA concentration, with a half-life of 2.1 ± 0.1 min. Experimental evidence indicates that NDMA oxidation proceeds via a direct electron transfer at potentials >1.8 V/SHE with a measured apparent activation energy of 3.1 ± 0.5 kJ/mol at a potential of 2.5 V/SHE. Density functional theory calculations indicate that a direct two-electron transfer can produce a stable NDMA(+2) species that is stabilized by forming an adduct with water. The transfer of two electrons from NDMA to the electrode allows an activation-less attack of hydroxyl radicals on the NDMA(+2) water adduct. At higher overpotentials the oxidation of NDMA occurs by a combination of direct electron transfer and hydroxyl radicals produced via water electrolysis.
ISSN:0013-936X
1520-5851
DOI:10.1021/es901582q