evaluated for the photodegradation of methylene blue in aqueous solution under UV
light irradiation. SiO 2 coating plays the role of a barrier between Fe 3 O 4 and TiO 2 that
improve photocatalytic properties and increase the dye adsorption capacity.
Although the photocatalytic activity of the Fe 3 O 4 /SiO 2 /TiO 2 composite is slightly
lower than the one of the commercial TiO 2 in terms of the amount of degraded
methylene blue, it can be easily collected from the aqueous solution after reaction by
using a magnetic bar.
For an economical and environmental point of view, the use of natural porous
materials as support for TiO 2 nanoparticles can present a great interest. TiO 2 -
modified kaolin photocatalysts have been prepared by physical mixing with P25
and impregnation with TiO 2 sol (Hajjaji et al. 2016). Good photocatalytic performances for the removal of methylene blue and orange II dyes from aqueous solutions
have been reported due to the combination of photocatalytic and adsorption processes. Diatomite, a natural porous silica material, was used as support for producing
TiO 2 /diatomite composites by a modified sol-gel method and a subsequent calcination step at different 450–950
C temperatures (Wang et al. 2015a, b). The presence
of an interfacial anchoring strength between the TiO 2 nanoparticles and diatom
skeleton via Si-O-Ti bonds has been shown. The best photocatalytic activity for
the photodegradation of rhodamine B was observed for the TiO 2 /diatomite composite calcined at 750
C for 2 h and having 90/10 weight ratio of anatase/rutile.
Hydroxyapatite/titania nanocomposites were synthesized by a dissolution/precipitation method from a titanium alkoxide and a natural phosphate. These low-cost
photocatalysts were found efficient for the removal of patent blue V and methylene
blue dyes from water by combination of adsorption and photodegradation processes.
Millimeter-size porous TiO 2 /alginate beads have been produced by an ionotropic
gelation route with commercial anatase titania powder (Gjipalaj and Alessandri
2017). The composite beads were found good adsorbents for anionic and cationic
dyes, such as methyl orange and methylene blue, respectively. However, their
photocatalytic efficiencies were observed and reduced compared to the
non-aggregated nanopowders. Nevertheless, they have the advantages to be easy
to recover and reusable, making them promising materials as green photocatalysts.
Porous carbon matrices such as activated carbon (Gao et al. 2011) or ordered
mesoporous carbon (Wei et al. 2014) have also been considered as interesting porous
support for TiO 2 nanoparticles because of the chemical inertness and stability in both
acid and basic media and tunable textural and chemical properties. The resulting
increase in photocatalytic performance for the degradation of organic pollutant such
as dyes has been related to their porosity. Larger pores were found preferable to
avoid the pore blockage by TiO 2 nanoparticles that results in lower dye adsorption
capacity. Nanostructured carbon materials such as carbon nanotubes, fullerenes,
graphene, and nanosheets have arisen increasing attention due to their unusual
structural and electronical properties (Wang and Zhang 2012). In particular,
graphene has emerged as one of the most promising materials to its large surface
area that improves dye adsorption capacity and its high electron mobility that
reduces the electron-hole pair recombination (Morales-Torres et al. 2012;
Giovannetti et al. 2017).
60
B. Lebeau et al.
light irradiation. SiO 2 coating plays the role of a barrier between Fe 3 O 4 and TiO 2 that
improve photocatalytic properties and increase the dye adsorption capacity.
Although the photocatalytic activity of the Fe 3 O 4 /SiO 2 /TiO 2 composite is slightly
lower than the one of the commercial TiO 2 in terms of the amount of degraded
methylene blue, it can be easily collected from the aqueous solution after reaction by
using a magnetic bar.
For an economical and environmental point of view, the use of natural porous
materials as support for TiO 2 nanoparticles can present a great interest. TiO 2 -
modified kaolin photocatalysts have been prepared by physical mixing with P25
and impregnation with TiO 2 sol (Hajjaji et al. 2016). Good photocatalytic performances for the removal of methylene blue and orange II dyes from aqueous solutions
have been reported due to the combination of photocatalytic and adsorption processes. Diatomite, a natural porous silica material, was used as support for producing
TiO 2 /diatomite composites by a modified sol-gel method and a subsequent calcination step at different 450–950
C temperatures (Wang et al. 2015a, b). The presence
of an interfacial anchoring strength between the TiO 2 nanoparticles and diatom
skeleton via Si-O-Ti bonds has been shown. The best photocatalytic activity for
the photodegradation of rhodamine B was observed for the TiO 2 /diatomite composite calcined at 750
C for 2 h and having 90/10 weight ratio of anatase/rutile.
Hydroxyapatite/titania nanocomposites were synthesized by a dissolution/precipitation method from a titanium alkoxide and a natural phosphate. These low-cost
photocatalysts were found efficient for the removal of patent blue V and methylene
blue dyes from water by combination of adsorption and photodegradation processes.
Millimeter-size porous TiO 2 /alginate beads have been produced by an ionotropic
gelation route with commercial anatase titania powder (Gjipalaj and Alessandri
2017). The composite beads were found good adsorbents for anionic and cationic
dyes, such as methyl orange and methylene blue, respectively. However, their
photocatalytic efficiencies were observed and reduced compared to the
non-aggregated nanopowders. Nevertheless, they have the advantages to be easy
to recover and reusable, making them promising materials as green photocatalysts.
Porous carbon matrices such as activated carbon (Gao et al. 2011) or ordered
mesoporous carbon (Wei et al. 2014) have also been considered as interesting porous
support for TiO 2 nanoparticles because of the chemical inertness and stability in both
acid and basic media and tunable textural and chemical properties. The resulting
increase in photocatalytic performance for the degradation of organic pollutant such
as dyes has been related to their porosity. Larger pores were found preferable to
avoid the pore blockage by TiO 2 nanoparticles that results in lower dye adsorption
capacity. Nanostructured carbon materials such as carbon nanotubes, fullerenes,
graphene, and nanosheets have arisen increasing attention due to their unusual
structural and electronical properties (Wang and Zhang 2012). In particular,
graphene has emerged as one of the most promising materials to its large surface
area that improves dye adsorption capacity and its high electron mobility that
reduces the electron-hole pair recombination (Morales-Torres et al. 2012;
Giovannetti et al. 2017).
60
B. Lebeau et al.