improvements are discussed. Also, the importance of the use of direct sunlight
irradiation for the photocatalytic water disinfection and its scale-up is discussed.
7.2 Nanostructured Materials for Water Disinfection
The nanostructured materials coupled with fine particles with a definite morphology
lead to large surface area and size, enhance the spectral absorption toward visible
wavelengths, and improve the photocatalytic oxidation of organic pollutants and
pathogens by reducing the photogenerated charge recombination. These nanostructured materials can be classified into three types: zero-dimensional,
one-dimensional, and two-dimensional materials. However, their efficiency for the
disinfection process depends on the preparation protocols allowing different light
absorption edges (ultraviolet and visible light) (Wang et al. 2017c).
7.2.1 Zero-Dimensional Nanostructures
Zero-dimensional nanostructure materials are characterized by a large surface area
populated by numerous active sites. Surface-dependent photocatalysts are getting
more attention from researchers working on water disinfection and remediation (Lee
and Jang 2014; Li et al. 2014).
According to Li et al. (2008a, b), four pathogenic microorganisms, namely, MS2
bacteriophage, poliovirus 1, herpes simplex virus, and hepatitis B virus, were
adequately disinfected by using nano-sized titanium oxide as a photocatalyst under
solar/UV radiation. Wei et al. (1994) have reported that the disinfection process
depends on the used light and the size of the TiO 2 particles. ZnO was found to
behave similarly to TiO 2 for the water disinfection process (Alikhani et al. 2012).
Barnes et al. (2013) investigated both TiO 2 and ZnO efficiencies in the disinfection
process of E. coli and B. subtilis. This study showed that TiO 2 nanoparticles
generated more reactive oxygen species than ZnO nanoparticles. However, ZnO
nanoparticles were more toxic to pathogenic microbes like E. coli and B. subtilis
even in the dark.
Li et al. (2014) explain that having small particle size does not mean to have
higher efficiency because the reduction in the number of hole layers makes the
generated reactive species to closely conjugate to each other and leads to decrease
the efficiency of the disinfection process, and this explains why the type of migration
is related to surface properties and morphology of the nanoparticle material (Lee and
Jang 2014; Li et al. 2014). Thus, more research shall be carried out in the future in
modifying, designing, and constructing between the surface properties and morphology of the nanocomposite material to ease the separation of reactive species as well
as increase the disinfection process (Lee and Jang 2014).
7 Photocatalytic Nanomaterials for Bacterial Disinfection
219
irradiation for the photocatalytic water disinfection and its scale-up is discussed.
7.2 Nanostructured Materials for Water Disinfection
The nanostructured materials coupled with fine particles with a definite morphology
lead to large surface area and size, enhance the spectral absorption toward visible
wavelengths, and improve the photocatalytic oxidation of organic pollutants and
pathogens by reducing the photogenerated charge recombination. These nanostructured materials can be classified into three types: zero-dimensional,
one-dimensional, and two-dimensional materials. However, their efficiency for the
disinfection process depends on the preparation protocols allowing different light
absorption edges (ultraviolet and visible light) (Wang et al. 2017c).
7.2.1 Zero-Dimensional Nanostructures
Zero-dimensional nanostructure materials are characterized by a large surface area
populated by numerous active sites. Surface-dependent photocatalysts are getting
more attention from researchers working on water disinfection and remediation (Lee
and Jang 2014; Li et al. 2014).
According to Li et al. (2008a, b), four pathogenic microorganisms, namely, MS2
bacteriophage, poliovirus 1, herpes simplex virus, and hepatitis B virus, were
adequately disinfected by using nano-sized titanium oxide as a photocatalyst under
solar/UV radiation. Wei et al. (1994) have reported that the disinfection process
depends on the used light and the size of the TiO 2 particles. ZnO was found to
behave similarly to TiO 2 for the water disinfection process (Alikhani et al. 2012).
Barnes et al. (2013) investigated both TiO 2 and ZnO efficiencies in the disinfection
process of E. coli and B. subtilis. This study showed that TiO 2 nanoparticles
generated more reactive oxygen species than ZnO nanoparticles. However, ZnO
nanoparticles were more toxic to pathogenic microbes like E. coli and B. subtilis
even in the dark.
Li et al. (2014) explain that having small particle size does not mean to have
higher efficiency because the reduction in the number of hole layers makes the
generated reactive species to closely conjugate to each other and leads to decrease
the efficiency of the disinfection process, and this explains why the type of migration
is related to surface properties and morphology of the nanoparticle material (Lee and
Jang 2014; Li et al. 2014). Thus, more research shall be carried out in the future in
modifying, designing, and constructing between the surface properties and morphology of the nanocomposite material to ease the separation of reactive species as well
as increase the disinfection process (Lee and Jang 2014).
7 Photocatalytic Nanomaterials for Bacterial Disinfection
219