Pyrylium salt-photosensitized degradation of phenolic contaminants derivedfrom cinnamic acid with solar light - Correlation of the observed reactivities with fluorescence quenching
Ma. Miranda et al., Pyrylium salt-photosensitized degradation of phenolic contaminants derivedfrom cinnamic acid with solar light - Correlation of the observed reactivities with fluorescence quenching, APP CATAL B, 28(2), 2000, pp. 127-133
Citations number
23
Categorie Soggetti
Physical Chemistry/Chemical Physics","Environmental Engineering & Energy
Solar light photodegradation of three cinnamic acid derivatives (ferulic ac
id, caffeic acid and p-coumaric acid) present in olive oil industry wastewa
ter has been achieved using 2,4,6-triphenylpyrylium hydrogen sulfate as an
electron transfer photosensitiser. The parent cinnamic acid undergoes no ph
otodegradation under the employed reaction conditions. The relative reactiv
ities are in agreement with expectations based on qualitative reasoning: th
e substrates with two electron-donating groups, ferulic and caffeic acid, r
eact faster than p-coumaric acid, which has only one activating substituent
; while the non-activated cinnamic acid is nearly unreactive. The data obta
ined from fluorescence measurements show that the excited singlet state of
the pyrylium salt is quenched by the acids, with the following rate constan
ts: 3.6 x 10(9) M-1 s(-1) for cinnamic acid, 4.4 x 10(10) M-1 s(-1) in the
cast: of p-coumaric acid, 8.7 x 10(10) M-1 s(-1) for caffeic acid, and 1.0
x 10(11) M-1 s(-1) for ferulic acid. These values are in good agreement wit
h the order of reactivities observed in the preparative solar reactions, (C
) 2000 Elsevier Science B.V. All rights reserved.