Identification of chlorinated oligomers formed during anodic oxidation of phenol in the presence of chloride

• Published in: Journal of hazardous materials 2015-01, Vol.283, p.574-581
• Main Authors: Chen, Linxi, Campo, Pablo, Kupferle, Margaret J.
• Format: Article
• Language: English
• Subjects: Anodic oxidation; Anodizing; Boron; Byproducts; Chlorides; Chlorides - chemistry; Chlorinated oligomers; Chlorination; Chromatography, Liquid; Diamond; Dioxins - chemistry; Electrodes; Halogenation; Liquid chromatography; Liquid chromatography quadrupole time-of-flight mass spectrometry; Mass Spectrometry; Oligomers; Oxidation-Reduction; Phenol; Phenol - chemistry; Triclosan - chemistry; Water Pollutants, Chemical - chemistry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2014.10.001

•By-products from anodic oxidation of phenol in the presence of chloride are investigated.•Chlorinated oligomer formation is demonstrated by LC-QTOF-MS.•They have structures similar to triclosan and polychlorinated dibenzo-p-dioxins. Chlorinated oligomer intermediates formed during the anodic electrochemical oxidation of phenol with a boron-doped diamond electrode were studied at two different concentrations of chloride (5mM and 50mM). Under the same ionic strength, with sodium sulfate being the make-up ion, a 10-fold increase in Cl− led to removal rates 10.8, 1.5, and 1.4 times higher for phenol, TOC, and COD, respectively. Mono-, di- and trichlorophenols resulting from electrophilic substitution were the identified by-products. Nevertheless, discrepancies between theoretical and measured TOC values along with gaps in the mass balance of chlorine-containing species indicated the formation of unaccounted-for chlorinated by-products. Accurate mass measurements by liquid chromatography quadrupole time-of-flight mass spectrometry and MS-MS fragmentation spectra showed that additional compounds formed were dimers and trimers of phenol with structures similar to triclosan and polychlorinated dibenzo-p-dioxins.