ACCELERATED PHOTOOXIDATION OF CONCENTRATED P-COUMARIC ACID IN HOMOGENEOUS SOLUTION - MECHANISTIC STUDIES, INTERMEDIATES AND PRECURSORS FORMED IN THE DARK
F. Herrara et al., ACCELERATED PHOTOOXIDATION OF CONCENTRATED P-COUMARIC ACID IN HOMOGENEOUS SOLUTION - MECHANISTIC STUDIES, INTERMEDIATES AND PRECURSORS FORMED IN THE DARK, Applied catalysis. B, Environmental, 17(1-2), 1998, pp. 141-156
This study shows that p-coumaric acid undergoes accelerated degradatio
n via photo-assisted Fenton reactions. Simulated solar radiation (90 m
W/cm(2)) promotes the full mineralization of a concentrated solution o
f p-coumaric acid (420 mg C/l) in less than 15 min when suitable times
for the oxidant addition were used in the presence of very low Fe-ion
concentration (4 mg Fe-ion/l). The mineralization of p-coumaric acid
has been studied as a function of the common variables as pH, concentr
ation of reagents and of the substrate used. The reduction of the tota
l organic compound (TOC) was observed to be a function of the surface-
to-volume (s/v) ratio on the reaction vessel due to the formation of l
ight induced radicals in the solution surface. Decoloration of these c
oncentrated solutions were observed in <1 min by stopped-flow techniqu
es. The most important reaction intermediates were determined by HPLC,
GC-MS and FTIR suggesting a reaction network for the degradation proc
ess. The Fenton reagent is shown to form precursor intermediates which
are susceptible to degradation under light. Degradation performed via
alternate dark and light cycles showed the importance of the dark pre
cursor species. Implications of this observation as an energy saving d
evice during the mineralization process is accounted for in this study
. (C) 1998 Elsevier Science B.V.