Environmental Engineering Reference
In-Depth Information
(a)
300
270
240
210
Photolysis
TiO
2
-P25
SG-600°C
SG-800°C
SS-950°C
180
150
120
90
60
30
0
0510
15
20
25 30
Time (min)
35
40
45
50
55
60
(b)
UV-A
180
Bi
2
InTaO
7
950°C
Bi
2
InTaO
7
800°C
TiO
2
P25
150
120
90
60
30
0
0510
15
20
25
30
35
40
45
50
55
60
Time (min)
figure 12.7
Photocatalytic removal of Marine Plankton, Algae-tide (a) and microorganism-tide (b) using Bi
2
InTaO
7
as a photocatalyst
under ultraviolet (UV) light. Reproduced with permission from Ref. [19]. © 2011, JCPR.
12.1.3 rectangular tunnel-type Structure: na
2
ti
6
o
13
It is well known that the photocatalytic process can be increased by surface modification of the photocatalysts by loading a
cocatalyst. The cocatalyst can be a noble metal (Pt and Rh) or a transition metal oxide (NiO and RuO
2
), which acts as an elec-
tron trap decreasing the electron-hole recombination process and also generates active sites for redox reactions.
Na
2
Ti
6
O
13
was obtained for the first time using the sol-gel method and tested as a photocatalyst in methylene blue deg-
radation [20, 21].The crystal structure of Na
2
Ti
6
O
13
is represented in Figure 12.8 where the presence of a tunnel structure
is observed.
Through scanning electron microscopy (SeM) micrographs the presence of the Na
2
Ti
6
O
13
compound was corroborated. This
material was obtained in the form of microrods (Fig. 12.9).
The photocatalytic evaluation of Na
2
Ti
6
O
13
on methylene blue revealed that the best photocatalytic performance on the deg-
radation of methylene blue under UV light was obtained using a photocatalyst sample heated at 400°C. However, total
crystallization of Na
2
Ti
6
O
13
occurred above 600°C; therefore, in this case, the activity reported for a sample at 400°C is influenced
by the presence of the amorphous material (Table 12.5).
