studied the influence of light and TiO 2 doping for the photodegradation of methylene
blue while comparing micro-channel and planar photocatalytic micro-reactors (Lin
et al. 2016). The planar micro-reactor was found to be more efficient than the microchannel one, and doped TiO 2 were reported to be more efficient than TiO 2 under
natural sunlight.
The influence of reaction parameters on the photodegradation rate and the global
process efficiency are strongly dependent on the reactor technology. Zhang et al.
reported that the photocatalytic degradation rate of methylene blue in a TiO 2 packed
bed micro-reactor was increased by 520 as compared to a conventional bulk container of 15 mL (Zhang et al. 2013). The implementation of a TiO 2 coated monolith
in a micro-reactor for the photocatalytic degradation of methylene blue was reported
by Teekateerawej et al. (Teekateerawej et al. 2005). Additionally to the TiO 2 coating
method, which influences the photocatalyst efficiency, they found that, in such
configuration, irradiation light angle is the main parameter governing the catalytic
reaction rate given that the light does not cross the monolith. Yang et al. compared
three mini-fluidized bed reactors for the photocatalytic degradation of methylene
blue (Yang et al. 2016). The first one with Fe
3+ /TiO 2 photocatalyst coated on the
inner wall of the reactor, the second one where the Fe
3+ /TiO 2 photocatalyst is coated
on the surface of fluidized particles (glass beads), and an third one with Fe
3+ /TiO 2
photocatalyst coated both on the wall of the reactor and on the fluidized glass beads.
The fluidization of glass beads allows increasing mass transfer coefficient by 11–13,
and apparent reaction rate constant is multiplied by 4.9. The third reactor combining
the two forms of catalyst (Fe
3+ /TiO 2 photocatalyst coated both on the wall of the
reactor and on the fluidized glass beads) was found to be 5 to 35% more efficient as
compared to the two other configurations.
Interestingly, Aran et al. reported a gas–liquid–solid heterogeneous
photocatalytic process by coupling a micro-reactor with a TiO 2 -based photocatalytic
membrane (Fig. 2.8) whose role is to ensure a continuous delivery of oxygen in the
aqueous feed (Aran et al. 2011). Advantageously, such a triphasic system
implemented at the microscale improves gas–liquid–solid interface. Authors
reported that the photocatalytic degradation rate of phenol was increased, thanks to
Fig. 2.8 Photocatalytic membrane-based triphasic flow reactor implemented by Aran et al.
(Reprinted with permission from Aran et al. 2011. Copyright 2011 Elsevier, Journal of Photochemistry and Photobiology A: Chemistry)
2 Dyes Depollution of Water Using Porous TiO 2 -Based Photocatalysts
75
blue while comparing micro-channel and planar photocatalytic micro-reactors (Lin
et al. 2016). The planar micro-reactor was found to be more efficient than the microchannel one, and doped TiO 2 were reported to be more efficient than TiO 2 under
natural sunlight.
The influence of reaction parameters on the photodegradation rate and the global
process efficiency are strongly dependent on the reactor technology. Zhang et al.
reported that the photocatalytic degradation rate of methylene blue in a TiO 2 packed
bed micro-reactor was increased by 520 as compared to a conventional bulk container of 15 mL (Zhang et al. 2013). The implementation of a TiO 2 coated monolith
in a micro-reactor for the photocatalytic degradation of methylene blue was reported
by Teekateerawej et al. (Teekateerawej et al. 2005). Additionally to the TiO 2 coating
method, which influences the photocatalyst efficiency, they found that, in such
configuration, irradiation light angle is the main parameter governing the catalytic
reaction rate given that the light does not cross the monolith. Yang et al. compared
three mini-fluidized bed reactors for the photocatalytic degradation of methylene
blue (Yang et al. 2016). The first one with Fe
3+ /TiO 2 photocatalyst coated on the
inner wall of the reactor, the second one where the Fe
3+ /TiO 2 photocatalyst is coated
on the surface of fluidized particles (glass beads), and an third one with Fe
3+ /TiO 2
photocatalyst coated both on the wall of the reactor and on the fluidized glass beads.
The fluidization of glass beads allows increasing mass transfer coefficient by 11–13,
and apparent reaction rate constant is multiplied by 4.9. The third reactor combining
the two forms of catalyst (Fe
3+ /TiO 2 photocatalyst coated both on the wall of the
reactor and on the fluidized glass beads) was found to be 5 to 35% more efficient as
compared to the two other configurations.
Interestingly, Aran et al. reported a gas–liquid–solid heterogeneous
photocatalytic process by coupling a micro-reactor with a TiO 2 -based photocatalytic
membrane (Fig. 2.8) whose role is to ensure a continuous delivery of oxygen in the
aqueous feed (Aran et al. 2011). Advantageously, such a triphasic system
implemented at the microscale improves gas–liquid–solid interface. Authors
reported that the photocatalytic degradation rate of phenol was increased, thanks to
Fig. 2.8 Photocatalytic membrane-based triphasic flow reactor implemented by Aran et al.
(Reprinted with permission from Aran et al. 2011. Copyright 2011 Elsevier, Journal of Photochemistry and Photobiology A: Chemistry)
2 Dyes Depollution of Water Using Porous TiO 2 -Based Photocatalysts
75