Photo-degradation of butyl parahydroxybenzoate by using
TiO
2
-supported catalyst
Patrick Atheba, Patrick Drogui, Brahima Seyhi and Didier Robert
ABSTRACT
The present work evaluates the potential of the photocatalysis (PC) process for the degradation of
butylparaben (BPB). Relatively high treatment efficiency was achieved by comparison to
photochemical process. Prior to photocatalytic degradation, adsorption (AD) of BPB occurred on the
titanium dioxide (TiO
2
)-supported catalyst. AD was described by Langmuir isotherm (K
L
¼ 0.085 L g
À1
,
q
m
¼ 4.77 mg g
À1
). The influence of angle of inclination of the reactor, pH, recirculation flow rate and
initial concentration of BPB were investigated. The PC process applied under optimal operating
conditions (recirculation flow rate of 0.15 L min
À1
, angle of inclination of 15
W
, pH ¼ 7 and 5 mg L
À1
of
BPB) is able to oxidize 84.9–96.6% of BPB and to ensure around 38.7% of mineralization. The
Langmuir–Hinshelwood kinetic model described well the photocatalytic oxidation of BPB (k ¼
7.02 mg L
À1
h
À1
, K ¼ 0.364 L mg
À1
).
Patrick Atheba
Patrick Drogui (corresponding author)
Brahima Seyhi
Institut national de la recherche scientifique
(INRS-Terre et Environnement),
Université du Québec,
490 rue de la Couronne,
Québec, Qc,
Canada G1K 9A9
E-mail: patrick.drogui@ete.inrs.ca
Didier Robert
Antenne de Saint-Avold du Laboratoire des
Matériaux,
Surface et Procédés pour la Catalyse (LMSPC)
UDS-CNRS-UMR7515,
Université de Lorraine,
12 rue Victor Demange 57500 Saint-Avold,
France Key words | adsorption, advanced oxidation process, butylparaben, kinetic, photocatalysis,
TiO
2
-supported
INTRODUCTION
Parabens are antimicrobial agents, antifungicidal agents and
antioxidants widely used in the cosmetic, pharmaceutical
and food industries (Nicoli et al. ; Gryglik et al. ;
Tay et al. ). Recent studies have shown the estrogenic
effect of parabens; in particular, propylparaben and butyl-
paraben (BPB) adversely affect the secretion of
testosterone and the function of the male reproductive
system in rats and mice (Terasaka et al. ; Nicoli et al.
; Bledzka et al. ). It has been proved that parabens
are able to easily penetrate the skin (Akomeah et al. ;
Nanayakkara et al. ; El Hussein et al. ) and to
reach unmodified the underlying tissues and the systemic
circulation (Soni et al. ; Nicoli et al. ). Parabens
are frequently found in aquatic environments because of
their broad application (Radovan et al. ; Bledzka et al.
). The concentrations of parabens in wastewaters are
in the range of ng L
À1
to μgL
À1
(Terasaki et al. ).
Recent studies demonstrated that parabens are biodegrad-
able, with half-lives lower than 3 days (Gonzalez-Marino
et al. ; Fan & Wang ). However, it has been shown
that conventional wastewater treatment plants release
organic pollutants such as parabens into aquatic environ-
ments (Gomez et al. ; Kasprzyk-Hordern et al. ;
Bledzka et al. ). The parabens are found in wastewater
treatment plant effluents and river water samples at a con-
centration level up to 0.085 μgL
À1
(Terasaki et al. ).
Many techniques are used such as chemical oxidation, bio-
logical oxidation, adsorption (AD), membrane filtration,
advanced oxidation processes (AOPs), etc. (Gallard & De
Laat ; Tahmasseb et al. ; Da Pozzo et al. ;
Esquivel et al. ). Chemical oxidation rarely leads to
total mineralization of pollutants. Biological oxidation is
considered to be very economical. However, it seems to be
inappropriate in many cases. Membrane filtration and AD
using activated carbon do not destroy the pollutants but
rather transfer them from one phase to another (Ozcan
et al. ; Tahir & Rauf ). AOPs including O
3
/H
2
O
2
,
UV/O
3
, UV/H
2
O
2
,H
2
O
2
/Fe
2þ
, etc., as well as photocataly-
sis (PC), have been identified as successful alternatives for
the destruction and mineralization of some recalcitrant
organic compounds (Naffrechoux et al. ; Gallard &
De Laat ). PC combines semiconductors acting as
photocatalysts, and UV irradiation. Under UV irradiation,
a multi-step process occurs involving the generation of
hydroxyl radical species (OH
o
), holes (h
þ
) able to oxidize
and mineralize many organic pollutants. The most
2141 © IWA Publishing 2013 Water Science & Technology | 67.10 | 2013
doi: 10.2166/wst.2013.117