which has been reported by Li et al. (Li et al. 2016). With 3D interpenetrating highly
porous structure and uniform 3–18 μm pores, the materials have showed high
adsorption capacity and an excellent photocatalytic performance for the degradation
of rhodamine B. Interestingly, sucrose has been added in the synthesis medium to
produce C-coating on the TiO 2 surface by sintering the solid at 500
C under N 2 . The
C-coating of macroporous TiO 2 ceramic has improved both the dye adsorption
capacity and the photodegradation rate of rhodamine B.
2.4.2 Nanoparticles and Nanotubes
When TiO 2 materials are synthesized as particles with nanosize, they result in high
specific surface area materials with exalted photocatalytic properties. TiO 2
nanoparticles have been widely studied for photodegradation of organic pollutants
in aqueous solutions and showed high potential for wastewater treatments. In
particular, they have been studied for their ability to decompose organic dyes in
aqueous solutions. There are several methods to synthesize TiO 2 nanomaterials such
as sol-gel, sol, hydrothermal, solvothermal, and chemical vapor deposition that are
well described in the recent review of M. M. Mahlambi et al. (2015). The synthesis
method and the experimental conditions are determinant on the structural and
textural characteristics such as crystalline phase, crystallinity degree, particle size,
and morphology, which directly influence the photocatalytic properties.
Nanoparticles can be prepared at low temperature via a sol-gel or sol route, but
result in TiO 2 amorphous phase and thus a subsequent thermal treatment has to be
applied to get the anatase TiO 2 crystalline phase. W-C. Lin et al. have prepared
anatase TiO 2 nanoparticles by using a sol-gel method with titanium isopropoxide
(TTIP), isopropanol as solvent, and acetylacetone (AcAc) as stabilizer for TTIP and
in the presence of polyethylene glycol that allowed controlling specific surface area
(Lin et al. 2012). The synthesis experimental conditions have been optimized with
the Taguchi experimental design method (L 9 (3
4 )). The post-synthesis calcination
treatment to form pure anatase nanoparticles was also investigated, and a temperature of 550
C was found optimal. The synthesized nanoparticles processed as
powder or as films have been shown to be efficient photocatalyst for the degradation
of methyl blue, methyl orange, and indigo dyes in water after 10 h of UV light
irradiation. Among the four parameters varied for the experimental design matrix,
the molar ratio AcAc/TTIP was found to have the greatest impact on the
photocatalytic degradation of dyes in water. It was also observed that the presence
of hydroxyl groups can improve the photocatalytic activity. The size of TiO 2
particles is also paramount of importance for photocatalytic efficiency. The influence
of the morphology on the photocatalytic activity of TiO 2 nanoparticles has been
investigated, and the nanorod shape aroused a particular interest. The sol-gel route
allows introducing polymers or block copolymers, amphiphilic, or not, in the
synthesis medium to control morphology, particles size, and aggregation. For a
practical and an economical point of view, it is highly desired to develop facile
54
B. Lebeau et al.
porous structure and uniform 3–18 μm pores, the materials have showed high
adsorption capacity and an excellent photocatalytic performance for the degradation
of rhodamine B. Interestingly, sucrose has been added in the synthesis medium to
produce C-coating on the TiO 2 surface by sintering the solid at 500
C under N 2 . The
C-coating of macroporous TiO 2 ceramic has improved both the dye adsorption
capacity and the photodegradation rate of rhodamine B.
2.4.2 Nanoparticles and Nanotubes
When TiO 2 materials are synthesized as particles with nanosize, they result in high
specific surface area materials with exalted photocatalytic properties. TiO 2
nanoparticles have been widely studied for photodegradation of organic pollutants
in aqueous solutions and showed high potential for wastewater treatments. In
particular, they have been studied for their ability to decompose organic dyes in
aqueous solutions. There are several methods to synthesize TiO 2 nanomaterials such
as sol-gel, sol, hydrothermal, solvothermal, and chemical vapor deposition that are
well described in the recent review of M. M. Mahlambi et al. (2015). The synthesis
method and the experimental conditions are determinant on the structural and
textural characteristics such as crystalline phase, crystallinity degree, particle size,
and morphology, which directly influence the photocatalytic properties.
Nanoparticles can be prepared at low temperature via a sol-gel or sol route, but
result in TiO 2 amorphous phase and thus a subsequent thermal treatment has to be
applied to get the anatase TiO 2 crystalline phase. W-C. Lin et al. have prepared
anatase TiO 2 nanoparticles by using a sol-gel method with titanium isopropoxide
(TTIP), isopropanol as solvent, and acetylacetone (AcAc) as stabilizer for TTIP and
in the presence of polyethylene glycol that allowed controlling specific surface area
(Lin et al. 2012). The synthesis experimental conditions have been optimized with
the Taguchi experimental design method (L 9 (3
4 )). The post-synthesis calcination
treatment to form pure anatase nanoparticles was also investigated, and a temperature of 550
C was found optimal. The synthesized nanoparticles processed as
powder or as films have been shown to be efficient photocatalyst for the degradation
of methyl blue, methyl orange, and indigo dyes in water after 10 h of UV light
irradiation. Among the four parameters varied for the experimental design matrix,
the molar ratio AcAc/TTIP was found to have the greatest impact on the
photocatalytic degradation of dyes in water. It was also observed that the presence
of hydroxyl groups can improve the photocatalytic activity. The size of TiO 2
particles is also paramount of importance for photocatalytic efficiency. The influence
of the morphology on the photocatalytic activity of TiO 2 nanoparticles has been
investigated, and the nanorod shape aroused a particular interest. The sol-gel route
allows introducing polymers or block copolymers, amphiphilic, or not, in the
synthesis medium to control morphology, particles size, and aggregation. For a
practical and an economical point of view, it is highly desired to develop facile
54
B. Lebeau et al.