Photocatalytic degradation of N-nitrosodimethylamine: Mechanism, product distribution, and TiO2 surface modification

Jaesang Lee, Wonyong Choi, Jeyong Yoon

Research output: Contribution to journalArticle

107 Citations (Scopus)

Abstract

The photocatalytic degradation (PCD) reaction of N-nitrosodimethylamine (NDMA) in water was investigated using pure and surface-modified TiO 2. The PCD products of NDMA were methylamine (MA), dimethylamine (DMA), nitrite, nitrate, and ammonium, and their distribution could be changed by modifying the surface of TiO2. The PCD reaction of NDMA seems to be initiated mostly by OH radicals, not valence band holes, because the addition of excess oxalates (hole scavengers) only moderately retarded the PCD rate. The presence of oxalate, however, enabled a new reductive transformation path in which the CO2 -• radicals generated from the oxalate converted NDMA into DMA. In acidic suspensions of pure TiO2, the formation of MA was highly favored over DMA and NH3, whereas all degradation products (MA, DMA, and NH3) were generated at comparable concentrations at basic pH. It is suggested that there are three parallel paths depending on the position of the initial attack of OH radical on NDMA and the product distribution is closely related with which path is favored under a specific condition. DMA production is related to the OH radical attack on the nitrosyl nitrogen. Platinum deposition, silica loading, Nafion coating, and surface fluorination were tested to investigate the effects of TiO2 surface modification on the product distribution. The surface platinization of TiO2 had little effect on the PCD reaction of NDMA under air-equilibrated conditions but accelerated the PCD reaction under deaerated conditions. An enhanced PCD reaction of NDMA was achieved with the silica-loaded TiO2 and Nafion-coated TiO2, both of which favored the formation of DMA over MA. The PCD of NDMA on surface-fluorinated TiO2 was also highly enhanced but favored the formation of MA over the formation of DMA.

Original languageEnglish
Pages (from-to)6800-6807
Number of pages8
JournalEnvironmental Science and Technology
Volume39
Issue number17
DOIs
Publication statusPublished - 2005 Sep 1
Externally publishedYes

Fingerprint

Dimethylnitrosamine
Surface treatment
Degradation
degradation
oxalate
Oxalates
Silicon Dioxide
silica
Silica
scavenger
product
distribution
Halogenation
platinum
Fluorination
nitrite
Nitrites
dimethylamine
Platinum
Ammonium Compounds

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Science(all)
  • Environmental Chemistry

Cite this

Photocatalytic degradation of N-nitrosodimethylamine : Mechanism, product distribution, and TiO2 surface modification. / Lee, Jaesang; Choi, Wonyong; Yoon, Jeyong.

In: Environmental Science and Technology, Vol. 39, No. 17, 01.09.2005, p. 6800-6807.

Research output: Contribution to journalArticle

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