membrane module with transmembrane pressure (TMP) of
70–350 mbar has shown a stable treatment result toward the
end of the operation. The outstanding of the pollution
parameters removal efficiencies with 100% removal of color
and suspended solids, 98% removal of COD and 96% of
biochemical oxygen demand (BOD 5 ) elimination has indicated that the process can be effectively operated for the
treatment of textile wastewater. Most importantly, this process has successfully decreased the toxicity of the
wastewater.
3.7 Photocatalytic Membrane
In recent years, the interest for advanced oxidation processes
(AOPs) has increased, especially heterogeneous photocatalytic processes. The heterogeneous photocatalytic process
starts with the irradiation of heterogenous semiconductors by
light irradiation as a source of energy. The electron excitation from the valence band to the conduction band upon light
irradiation will generate electron–hole pairs that can react
with water and dissolved oxygen to form various oxidizing
species such as hydroxyl superoxide and perhydroxyl radicals. These highly reactive oxidizing species are able to
oxidize and mineralize completely various organic contaminants (Kamat 1993).
Typically, semiconductors such as titanium dioxide
(TiO 2 ), zinc oxide (ZnO), cadmium sulfide (CdS) and zinc
sulfide (ZnS) are employed in photocatalysis due to their
electronic structure (Saggioro et al. 2011). Interestingly,
TiO 2 is the most common heterogenous photocatalyst with
good photocatalytic activity due to its ideal properties such
as nontoxic, chemical inertness and low-cost operation.
Despite the excellent performance, the main limitation of the
photocatalytic process is the recovery of the photocatalyst
from the solution. To overcome this problem, heterogeneous
photocatalytic oxidation may be combined with different
membrane processes, such as microfiltration (MF),
ultrafiltration (UF), nanofiltration (NF) and direct contact
membrane distillation (DCMD, MD) (Buscio et al. 2015). In
the meantime, photocatalytic membrane reactors (PMRs)
divided into reactors with suspended photocatalyst and
photocatalysts suspended in a feed solution and (II) reactors
with immobilized photocatalysts (Mendret et al. 2013)
(Fig. 13).
The MPR offers several advantages for textile wastewater
treatment such as continuous treatment process with simultaneous separation of photocatalyst from the reaction environment and constantly confined the photocatalyst in the
reaction surrounding. Additionally, MPR also able to control
the molecules retention time in a reactor. These remarkable
improvements provided by MPR over the conventional
treatments will ensure efficient treatment to decolorize,
detoxify and treat industrial dye wastewater. Table 8 shows
various photocatalytic MPR used for the degradation of
textile wastewater.
Several issues have to be improved in order to increase
the feasibility of photocatalysis process for textile wastewater treatment in the future. The most important is the
development of a photocatalyst with high photo-efficiency
under the irradiation of a wider solar spectra. Besides, catalyst immobilization strategies need to be addressed properly
to provide a cost effective for the separation of photocatalyst
from the reaction environment. There is also a need for the
improvement in the photocatalytic reaction for wider pH
range as well as to minimize the addition of oxidizing
agents. Finally, good photocatalytic reactor with an effective
design would significantly reduce the electricity costs
without jeopardizing its performances.
4 Conclusions and Recommendation
Textile effluents in the organisms cause bio-toxicity, subsequent in growth inhibition and low plant chlorophyll content. Alternative treatments need to be found that are efficient
Fig. 13 Photocatalytic
membrane photoreactor
(MPR) for a Suspension
photocatalyst and b Immobilized
photocatalyst
Advanced Membrane Technology for Textile Wastewater Treatment
105
70–350 mbar has shown a stable treatment result toward the
end of the operation. The outstanding of the pollution
parameters removal efficiencies with 100% removal of color
and suspended solids, 98% removal of COD and 96% of
biochemical oxygen demand (BOD 5 ) elimination has indicated that the process can be effectively operated for the
treatment of textile wastewater. Most importantly, this process has successfully decreased the toxicity of the
wastewater.
3.7 Photocatalytic Membrane
In recent years, the interest for advanced oxidation processes
(AOPs) has increased, especially heterogeneous photocatalytic processes. The heterogeneous photocatalytic process
starts with the irradiation of heterogenous semiconductors by
light irradiation as a source of energy. The electron excitation from the valence band to the conduction band upon light
irradiation will generate electron–hole pairs that can react
with water and dissolved oxygen to form various oxidizing
species such as hydroxyl superoxide and perhydroxyl radicals. These highly reactive oxidizing species are able to
oxidize and mineralize completely various organic contaminants (Kamat 1993).
Typically, semiconductors such as titanium dioxide
(TiO 2 ), zinc oxide (ZnO), cadmium sulfide (CdS) and zinc
sulfide (ZnS) are employed in photocatalysis due to their
electronic structure (Saggioro et al. 2011). Interestingly,
TiO 2 is the most common heterogenous photocatalyst with
good photocatalytic activity due to its ideal properties such
as nontoxic, chemical inertness and low-cost operation.
Despite the excellent performance, the main limitation of the
photocatalytic process is the recovery of the photocatalyst
from the solution. To overcome this problem, heterogeneous
photocatalytic oxidation may be combined with different
membrane processes, such as microfiltration (MF),
ultrafiltration (UF), nanofiltration (NF) and direct contact
membrane distillation (DCMD, MD) (Buscio et al. 2015). In
the meantime, photocatalytic membrane reactors (PMRs)
divided into reactors with suspended photocatalyst and
photocatalysts suspended in a feed solution and (II) reactors
with immobilized photocatalysts (Mendret et al. 2013)
(Fig. 13).
The MPR offers several advantages for textile wastewater
treatment such as continuous treatment process with simultaneous separation of photocatalyst from the reaction environment and constantly confined the photocatalyst in the
reaction surrounding. Additionally, MPR also able to control
the molecules retention time in a reactor. These remarkable
improvements provided by MPR over the conventional
treatments will ensure efficient treatment to decolorize,
detoxify and treat industrial dye wastewater. Table 8 shows
various photocatalytic MPR used for the degradation of
textile wastewater.
Several issues have to be improved in order to increase
the feasibility of photocatalysis process for textile wastewater treatment in the future. The most important is the
development of a photocatalyst with high photo-efficiency
under the irradiation of a wider solar spectra. Besides, catalyst immobilization strategies need to be addressed properly
to provide a cost effective for the separation of photocatalyst
from the reaction environment. There is also a need for the
improvement in the photocatalytic reaction for wider pH
range as well as to minimize the addition of oxidizing
agents. Finally, good photocatalytic reactor with an effective
design would significantly reduce the electricity costs
without jeopardizing its performances.
4 Conclusions and Recommendation
Textile effluents in the organisms cause bio-toxicity, subsequent in growth inhibition and low plant chlorophyll content. Alternative treatments need to be found that are efficient
Fig. 13 Photocatalytic
membrane photoreactor
(MPR) for a Suspension
photocatalyst and b Immobilized
photocatalyst
Advanced Membrane Technology for Textile Wastewater Treatment
105