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 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/m(2)-hr were observed at a current density of 10 mA/cm(2). 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.
Chaplin
Brian P
BP
Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721, USA. chaplin1@email.arizona.edu
Schrader
Glenn
G
Farrell
James
J
D001895:Boron / Q000737:chemistry*; D018130:Diamond / Q000737:chemistry*; D004128:Dimethylnitrosamine / Q000737:chemistry* / Q000302:isolation & purification; D004560:Electricity; D055664:Electrochemical Techniques; D004566:Electrodes; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013816:Thermodynamics; D013997:Time Factors
D018130:Diamond; D004128:Dimethylnitrosamine; D001895:Boron