IJUP08 - Universidade do Porto

PHOTOCATALYTIC DEGRADATION OF CIPROFLOXACIN
ANTIBIOTIC IN TiO2 AQUEOUS SUSPENSION
F. G. Azevedo, M. Domingos, C. G. Silva and J. L. Faria
Laboratório de Catálise e Materiais, Departamento de Engenharia Química, Faculdade de
Engenharia, Universidade do Porto, Rua Dr. Roberto Frias 4200-465 Porto, Portugal
The presence of pharmaceuticals and their metabolites in aquatic environments has raised
increasing concern in recent years [1]. Antibiotics can hardly be degraded by biological
processes, leading to the persistence of these compounds in the aquatic ecosystem posing a
real threat in what concerns bio-accumulation. Hence, it is a priority to search for
alternative chemical treatment methods, which can effectively eliminate the disposed
amounts of this type of compounds. Ciprofloxacin (CIPRO) is an antibacterial drug
belonging to the class of fluoroquinolones, widely used in the treatment of severe
infections in humans. Among the possible treatments, TiO2-mediated photocatalysis has
proven to be very effective in the complete oxidation of a great variety of organic
pollutants [2]. The process is based in the oxidative potential of the hydroxyl radical
(HO • ), which reacts rapidly and non-selectively with a wide range of organic compounds.
In this work, it is shown that CIPRO can be degraded in an aqueous suspension of TiO2
(Degussa P-25) using ultraviolet (253.7
nm) radiation, more efficiently that in the
absence of any photocatalyst (Fig 1). The
photocatalytic process leads to a total
organic carbon removal of 80% after two
hours of irradiation.
The aim of this study is to examine the
mechanism of photocatalytic reaction.
The effects on the reaction of the TiO2
catalyst loading, CIPRO initial
concentration (C0), pH, irradiation
intensity and dissolved oxygen
concentration are described. A kinetic
model to describe the contribution of the
mentioned variables will be attempted.
0.0
0 10 20 30 40 50 60 70 80 90 100 110 120
Acknowledgments: The authors gratefully acknowledge FCT and FEDER for financial
assistance (fellowship SFRH/BD/16966/2004 and projects POCI/EQU/58252/2004 and
POCTI/1181/2003).
References:
[1] Hirsch, R., Ternes, T., Haberer, K. and Kratz, K.-L. (1999), Occurrence of Antibiotics in the
Aquatic Environment, The Science of the Total Environment, 225(1-2), 109-118.
[2] Silva, C.G., Wang, W. and Faria, J.L. (2006), Photocatalytic and Photochemical Degradation
of Mono-, Di- and Tri-azo Dyes in Aqueous Solution Under UV Irradiation, Journal of
Photochemistry and Photobiology A: Chemistry, 181(2-3), 314-324.
C/C0
1.0
0.8
0.6
0.4
0.2
UV/TiO 2
UV
Time (min)
Fig. 1- CIPRO decay during photochemical (UV)
and photocatalytic (UV/TiO2) reactions.
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