title: Electrochemical destruction of N-nitrosodimethylamine in reverse osmosis concentrates using Boron-doped diamond film electrodes.
abstract: Boron-doped diamond (BDD) film electrodes were use to electrochemically destroy N-nitrosodimethylamine (NDMA) in reverse osmosis (RO) concentrates. Batch experiments were conducted ito investigate the effects of dissolved organic carbon (DOC), chloride (Cl(-)), bicarbonate (HCO(3-) and hardness on rates of NDMA destruction via both oxidation and reduction. Experimental results showed that NDMA oxidation rates were not affected by DOC, Cl(-), or HCO(3-) at concentrations present in RO concentrates. However, hydroxyl radical scavenging at 100 mM concentrations of HCO(3-) and Cl(-) shifted the reaction mechanism of NDMA oxidation from hydroxyl radical mediated to direct electron transfer oxidation. In the 100 mM Cl(-) electrolyte experimental evidence suggests that the in situ production of ClO(3)(.)also contributes to NDMA oxidation. Density functional theory calculations support a reaction mechanism between ClO(3)(.) and NDMA, with an activation barrier of 7.2 kJ/mol. Flow-through experiments with RO concentrate yielded surface area normalized first-order rate constants for NDMA (40.6 +/- 3.7 L/m(2) h) and DOC (as C) (38.3 +/- 2.2 L/m(2) h) removal that were mass transfer limited at a 2 mA/cm(2) current density. This research shows that electrochemical oxidation using BDD electrodes has an advantage over other advanced oxidation processes, as organics were readily oxidized in the presence of high HCO(3-) concentrations.
authors.affiliation: Department of Chemical and Environmental Engineering University of Arizona, Tucson, Arizona 85721, USA. chaplin1@email.arizona.edu
authors.forename: Brian P
authors.initials: BP
authors.lastname: Chaplin
authors.forename: Glenn
authors.initials: G
authors.lastname: Schrader
authors.forename: James
authors.initials: J
authors.lastname: Farrell
mesh_terms: D001895:Boron; D002851:Chromatography, High Pressure Liquid; D018130:Diamond; D004128:Dimethylnitrosamine / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D007700:Kinetics; D009995:Osmosis; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet
chemical_list: D018130:Diamond; D004128:Dimethylnitrosamine; D001895:Boron