Tixier et al. 2003). However, generally, the concentrations of the pharmaceutical
pollutants and photocatalysts used in the laboratories varied from 20 to 200 mg/L
and 0.2–1.5 g/L, respectively (Palominos et al. 2009; Mohammadi et al. 2012).
Many pharmaceutical drugs, i.e., ibuprofen (IBP), atenolol (ATL), and carbamazepine (CBZ), are subjects of various studies, (Hapeshi et al. 2010; Georgaki et al.
2014) which employed immobilized TiO 2 systems (Khataee et al. 2013; Sarkar et al.
2015; He et al. 2016). Thus, heterogeneous photocatalysis using TiO 2 nanoparticles
has become a promising pathway for elimination of several micropollutants from
wastewater (Zhang et al. 2010a; An et al. 2011; Sarkar et al. 2014a, b). Small size
nanoparticles provide higher surface to volume ratio and thus offer better surface
reactivity.
The influence of some doping atoms on the surface reactivity of titanium oxidebased materials is crucial. For example, it was reported that the 2p orbital of nitrogen
makes it the most easily binding element with the 2p orbital of oxygen among the
nonmetal dopants incorporated to titanium oxide. Thus, nitrogen atoms are located
in position of oxygen in TiO 2 lattice to form O-Ti-N structure (Schneider et al.
2014). The photocatalytic mechanism of N-doping CNT/TiO 2 under visible light has
been proposed by Schneider et al. (2014 and Yuan et al. 2016) The smaller band-gap
of N-doping CNT/TiO 2 is mainly resulted from both the polymorphs of TiO 2 and
doping with nitrogen, leading to the good separation of (e
À /h
+
) pairs under visible
light region (Fig. 7.7). The same result was observed by Calza et al. using TiO 2
doped with graphene oxide at various irradiated media under simulated solar irradiation (Calza et al. 2016).
The degradation of IBP by several oxidation processes has already been reported.
Lambropoulou et al. studied the TiO 2 photocatalytic degradation of IBP and
diclofenac (DCF) pharmaceutical compounds (Lambropoulou et al. 2011). They
have suggested that during the application of TiO 2 photocatalysis under UV light,
simulated solar, and ultrasound irradiation, numerous transformation products are
formed since ÁOH does not exhibit selectivity toward various functional groups,
while other reactive species (e.g., O 2
ÀÁ , h
+
, or e
À ) participate in multiple oxidoreductive pathways (Lambropoulou et al. 2011). Different degradation pathways can
be put forward, in which hydroxylation, demethylation, decarboxylation, cleavage
of isobutyl moiety, and oxidation of hydroxyl groups are described as major steps
during the transformation processes (Scheme 7.1) (Michael et al. 2014).
Madhavan et al. studied the photocatalytic degradation of IBP in presence of TiO 2
and reported that the formation of hydroxylated products argued that the hydroxylation process could be the first step of the degradation, followed by a second step of
demethylation or decarboxylation with other different by-products with smaller m/z
values (Madhavan et al. 2010). The formation of hydroxylated products (I) and (II) is
observed in all the processes using photocatalysis for degradation. In addition, the
products with m/z values 133 and 191 corresponding to 4-ethylbenzaldehyde (III)
and 4-(1-carboxyethyl)benzoic acid (IV) were also detected (Fig. 7.8).
The relationship between commercial TiO 2 and the photocatalyst activity with
the molecular volume of the drugs has been recently studied (da Silva et al. 2015). A
228
A. Boudjemaa and S. Gómez-Ruiz
pollutants and photocatalysts used in the laboratories varied from 20 to 200 mg/L
and 0.2–1.5 g/L, respectively (Palominos et al. 2009; Mohammadi et al. 2012).
Many pharmaceutical drugs, i.e., ibuprofen (IBP), atenolol (ATL), and carbamazepine (CBZ), are subjects of various studies, (Hapeshi et al. 2010; Georgaki et al.
2014) which employed immobilized TiO 2 systems (Khataee et al. 2013; Sarkar et al.
2015; He et al. 2016). Thus, heterogeneous photocatalysis using TiO 2 nanoparticles
has become a promising pathway for elimination of several micropollutants from
wastewater (Zhang et al. 2010a; An et al. 2011; Sarkar et al. 2014a, b). Small size
nanoparticles provide higher surface to volume ratio and thus offer better surface
reactivity.
The influence of some doping atoms on the surface reactivity of titanium oxidebased materials is crucial. For example, it was reported that the 2p orbital of nitrogen
makes it the most easily binding element with the 2p orbital of oxygen among the
nonmetal dopants incorporated to titanium oxide. Thus, nitrogen atoms are located
in position of oxygen in TiO 2 lattice to form O-Ti-N structure (Schneider et al.
2014). The photocatalytic mechanism of N-doping CNT/TiO 2 under visible light has
been proposed by Schneider et al. (2014 and Yuan et al. 2016) The smaller band-gap
of N-doping CNT/TiO 2 is mainly resulted from both the polymorphs of TiO 2 and
doping with nitrogen, leading to the good separation of (e
À /h
+
) pairs under visible
light region (Fig. 7.7). The same result was observed by Calza et al. using TiO 2
doped with graphene oxide at various irradiated media under simulated solar irradiation (Calza et al. 2016).
The degradation of IBP by several oxidation processes has already been reported.
Lambropoulou et al. studied the TiO 2 photocatalytic degradation of IBP and
diclofenac (DCF) pharmaceutical compounds (Lambropoulou et al. 2011). They
have suggested that during the application of TiO 2 photocatalysis under UV light,
simulated solar, and ultrasound irradiation, numerous transformation products are
formed since ÁOH does not exhibit selectivity toward various functional groups,
while other reactive species (e.g., O 2
ÀÁ , h
+
, or e
À ) participate in multiple oxidoreductive pathways (Lambropoulou et al. 2011). Different degradation pathways can
be put forward, in which hydroxylation, demethylation, decarboxylation, cleavage
of isobutyl moiety, and oxidation of hydroxyl groups are described as major steps
during the transformation processes (Scheme 7.1) (Michael et al. 2014).
Madhavan et al. studied the photocatalytic degradation of IBP in presence of TiO 2
and reported that the formation of hydroxylated products argued that the hydroxylation process could be the first step of the degradation, followed by a second step of
demethylation or decarboxylation with other different by-products with smaller m/z
values (Madhavan et al. 2010). The formation of hydroxylated products (I) and (II) is
observed in all the processes using photocatalysis for degradation. In addition, the
products with m/z values 133 and 191 corresponding to 4-ethylbenzaldehyde (III)
and 4-(1-carboxyethyl)benzoic acid (IV) were also detected (Fig. 7.8).
The relationship between commercial TiO 2 and the photocatalyst activity with
the molecular volume of the drugs has been recently studied (da Silva et al. 2015). A
228
A. Boudjemaa and S. Gómez-Ruiz