of ceramic (Alem et al. 2009; Romanos et al. 2013) or metallic (Bellobono et al.
2005) membranes, but the main drawback of such membranes is their cost.
In the second configuration, the non-photoactive separation layer is deposited on
a photoactive support. The light source is located in the photoactive support side. In
such configuration, filtration (membrane) and photocatalysis (photoactive support)
are separated. Such configuration allows obtaining a higher permeate quality and
prevents the membrane degradation by UV radiation (Mozia 2010). The main
drawbacks are that only the permeate is purified, the possible fouling of the
non-photoactive membrane and the non-degradation of high molecular weight
organics. Indeed, such large molecules are blocked by the pore size of the membrane
and thus cannot cross the membrane to reach the photocatalytic support. Both
configurations were compared by Bosc et al. by using mesoporous TiO 2 -based
membranes for the photocatalytic degradation of methylene blue (Bosc et al. 2005).
Romanos et al. even implemented “double-side active photocatalytic ultrafiltration
(UF) membranes” which consists in coating and irradiating both sides of the
membrane (Romanos et al. 2013). From their results on the photocatalytic degradation of methyl orange, authors claimed that such a process exhibits similar performances as compared to the highly efficient standard nanofiltration and with the
advantages such as lower energy consumption without the generation of toxic
by-products.
Several studies report dye photodegradation through photocatalytic membranes
(TiO 2 immobilized on/in the membrane) (Zhang et al. 2006a; Wang et al. 2008;
Papageorgiou et al. 2012; Mendret et al. 2013; Romanos et al. 2013; Zhang et al.
2014).
Zhang et al. reported the synthesis of a TiO 2 hollow fiber-based membrane, which
was evaluated for the photocatalytic degradation of acid orange 7 (Zhang et al.
2014). The influence of the calcination temperature was found to strongly influence
membrane properties: the higher the calcination temperature, the smaller the pore
size and the photocatalytic activity, the higher the mechanical robustness. The best
calcination temperature was reported to be 900
C, which allows removing 90.2% of
organics at a water flux of 12.2 L.m
À2 .h
À1 .
Alem et al. reported the synthesis of a multilayer mesoporous TiO 2 coated on
alumina membrane with a high surface area (83 m
2 .g
À1 and a pore size of 4 nm) for
the photodegradation of methyl orange (Alem et al. 2009). Such membrane allows
increasing the photocatalytic activity by 60% without sacrificing its permeation
compared to colloidal monolayer membrane. Mendret et al. reported the
photodegradation of acid orange 7 on a TiO 2 /Al 2 O 3 membrane (Mendret et al.
2013). They found that such a process enhances ceramic membrane wettability
and allows preventing membrane fouling while improving flux stability. Moreover,
membrane cleaning was performed by irradiating membrane surface under static
conditions, without chemicals. Papageorgiou et al. 2012 implemented
photocatalytic/ultrafiltration process using a composite of AEROXIDE® TiO 2 P25
and alginate polymer fiber-based membrane which were found to be threefold more
efficient than conventional membrane for the photocatalytic degradation of methyl
orange (Papageorgiou et al. 2012).
2 Dyes Depollution of Water Using Porous TiO 2 -Based Photocatalysts
69
2005) membranes, but the main drawback of such membranes is their cost.
In the second configuration, the non-photoactive separation layer is deposited on
a photoactive support. The light source is located in the photoactive support side. In
such configuration, filtration (membrane) and photocatalysis (photoactive support)
are separated. Such configuration allows obtaining a higher permeate quality and
prevents the membrane degradation by UV radiation (Mozia 2010). The main
drawbacks are that only the permeate is purified, the possible fouling of the
non-photoactive membrane and the non-degradation of high molecular weight
organics. Indeed, such large molecules are blocked by the pore size of the membrane
and thus cannot cross the membrane to reach the photocatalytic support. Both
configurations were compared by Bosc et al. by using mesoporous TiO 2 -based
membranes for the photocatalytic degradation of methylene blue (Bosc et al. 2005).
Romanos et al. even implemented “double-side active photocatalytic ultrafiltration
(UF) membranes” which consists in coating and irradiating both sides of the
membrane (Romanos et al. 2013). From their results on the photocatalytic degradation of methyl orange, authors claimed that such a process exhibits similar performances as compared to the highly efficient standard nanofiltration and with the
advantages such as lower energy consumption without the generation of toxic
by-products.
Several studies report dye photodegradation through photocatalytic membranes
(TiO 2 immobilized on/in the membrane) (Zhang et al. 2006a; Wang et al. 2008;
Papageorgiou et al. 2012; Mendret et al. 2013; Romanos et al. 2013; Zhang et al.
2014).
Zhang et al. reported the synthesis of a TiO 2 hollow fiber-based membrane, which
was evaluated for the photocatalytic degradation of acid orange 7 (Zhang et al.
2014). The influence of the calcination temperature was found to strongly influence
membrane properties: the higher the calcination temperature, the smaller the pore
size and the photocatalytic activity, the higher the mechanical robustness. The best
calcination temperature was reported to be 900
C, which allows removing 90.2% of
organics at a water flux of 12.2 L.m
À2 .h
À1 .
Alem et al. reported the synthesis of a multilayer mesoporous TiO 2 coated on
alumina membrane with a high surface area (83 m
2 .g
À1 and a pore size of 4 nm) for
the photodegradation of methyl orange (Alem et al. 2009). Such membrane allows
increasing the photocatalytic activity by 60% without sacrificing its permeation
compared to colloidal monolayer membrane. Mendret et al. reported the
photodegradation of acid orange 7 on a TiO 2 /Al 2 O 3 membrane (Mendret et al.
2013). They found that such a process enhances ceramic membrane wettability
and allows preventing membrane fouling while improving flux stability. Moreover,
membrane cleaning was performed by irradiating membrane surface under static
conditions, without chemicals. Papageorgiou et al. 2012 implemented
photocatalytic/ultrafiltration process using a composite of AEROXIDE® TiO 2 P25
and alginate polymer fiber-based membrane which were found to be threefold more
efficient than conventional membrane for the photocatalytic degradation of methyl
orange (Papageorgiou et al. 2012).
2 Dyes Depollution of Water Using Porous TiO 2 -Based Photocatalysts
69