title: Electrospray ionization mass spectrometry of the photodegradation of naphthenic acids mixtures irradiated with titanium dioxide.
abstract: Electrospray ionization mass spectrometry was used to study the photodegradation of an oil sands naphthenic acid (NA) mixture, a commercial Fluka NA mixture and a candidate NA, 4-Methyl-cyclohexaneaceticic acid (4-MCHAA) irradiated with TiO(2) (P25) suspension under both fluorescent and natural sunlight. Under natural sunlight irradiation over the TiO(2) suspension, approximately 75% of compounds in the NA mixtures and 100% of 4-MCHAA were degraded in 8 h. No degradation was observed under dark conditions, regardless of the presence or absence of TiO(2). The structural formula of the NAs is given by C(n)H(2n + z)O(2), where n represents the carbon number and z specifies a homologous family with 0-6 rings (z = 0 to -12). The degree of degradation was noted to vary among the NA mixtures and the candidate NA compound with more efficient degradation achieved for molecules with -z values from 0 to 6. The difference in the efficacy of the photocatalysis was likely due to the structure and size of the compounds. In the case of -z = 6 to 12, steric constraints are a key factor what hinders photocatalysis.
authors.affiliation: Water Science and Technology Directorate, Aquatic Ecosystem Protection Research Division, Environment Canada, Saskatoon, SK, Canada. john.headley@ec.gc.ca
authors.forename: John V
authors.initials: JV
authors.lastname: Headley
authors.forename: Jing-Long
authors.initials: JL
authors.lastname: Du
authors.forename: Kerry M
authors.initials: KM
authors.lastname: Peru
authors.forename: Dena W
authors.initials: DW
authors.lastname: McMartin