Laminar falling film slurry (LFFS) photocatalytic reactors are one of the m
ost efficient reactor configurations for conducting heterogeneous photocata
lytic reactions, particularly for wastewater treatment. This paper presents
a study on the oxidation of an aqueous salicylic acid waste in a pilot con
tinuous flow LFFS photocatalytic reactor which has an optimum design for li
ght absorption. In conducting the oxidation reaction, heterogeneous photoca
talysis was supplemented with other photon-assisted processes. The effect o
f light intensity, radiation wavelength, oxidizing-enhancing agents, substr
ate and photocatalyst concentration, and exposure time were studied. A comp
arison of six different photon-based processes showed that higher oxidation
rates of salicylic acid were obtained when there was concomitant photocata
lysis, photolysis, and UV peroxidation. The oxidation rates of salicylic ac
id with this combined process were at least 1 order of magnitude higher in
comparison with those for UVA photocatalysis and 3-fold higher in compariso
n with homogeneous UVC photolysis/UVC peroxidation.