Urea degradation by electrochemically generated reactive chlorine species: products and reaction pathways
SCIE
SCOPUS
- Title
- Urea degradation by electrochemically generated reactive chlorine species: products and reaction pathways
- Authors
- CHO, KANGWOO; Michael R. Hoffmann
- Date Issued
- 2014-10-07
- Publisher
- AMER CHEMICAL SOC
- Abstract
- This study investigated the transformation of urea by electrochemically generated reactive chlorine species (RCS). Solutions of urea with chloride ions were electrolyzed using a bismuth doped TiO2 (BiOx/TiO2) anode coupled with a stainless steel cathode at applied anodic potentials (E-a) of either +2.2 V or +3.0 V versus the normal hydrogen electrode. In NaCl solution, the current efficiency of RCS generation was near 30% at both potentials. In divided cell experiments, the pseudo-first-order rate of total nitrogen decay was an order of magnitude higher at E-a of +3.0 V than at +2.2 V, presumably because dichlorine radical (Cl-2(-)) ions facilitate the urea transformation primary driven by free chlorine. Quadrupole mass spectrometer analysis of the reactor headspace revealed that N-2 and CO2 are the primary gaseous products of the oxidation of urea, whose urea-N was completely transformed into N-2 (91%) and NO- (9%). The higher reaction selectivity with respect to N-2 production can be ascribed to a low operational ratio of free available chlorine to N. The mass-balance analysis recovered urea-C as CO2 at 77%, while CO generation most likely accounts for the residual carbon. In light of these results, we propose a reaction mechanism involving chloramines and chloramides as reaction intermediates, where the initial chlorination is the rate-determining step in the overall sequence of reactions.
- Keywords
- SOURCE-SEPARATED URINE; ACTIVE CHLORINE; SWIMMING POOLS; WATER; OXIDATION; AMMONIA; ELECTRODES; MECHANISM; NITROGEN; DECOMPOSITION
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/40863
- DOI
- 10.1021/es5025405
- ISSN
- 0013-936X
- Article Type
- Article
- Citation
- ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol. 48, no. 19, page. 11504 - 11511, 2014-10-07
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