Environmental Engineering Reference
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tartaric acid solution. h e strength of the Ti
4+
solution was estimated by
gravimetric method.
In the second step, the equivalent amount of metal nitrate, (NH
4
)
2
MoO
4
and titanium tartarate solution were taken in a beaker as per chemical
composition. h e complexing agent TEA (triethanolamine) (where molec-
ular ratio of metal ion:TEA = 1:3) was added to the homogeneous solution
of constituents maintaining pH at 4-7 by nitric acid and ammonia. h is
mixed solution at er evaporation and decompositions at 200
o
C, resulted in
black carbonaceous light porous mass, which was followed by calcination
in air at temperatures 500-750
C for 2 h at a heating rate of 5% min for
dif erent chemical compositions.
Recently, mesoporous nanoclusters of M
x
Nb
x
Ti
1-2x
O
2-x/2
(M = Cr, Fe; x =
0.01, 0.05, 0.1, 0.2) were prepared by sol-gel method [89]. h e total synthe-
sis was carried out in two steps. In the i rst step, the stock solutions of ferric
nitrate, titanium tartarate and niobium tartarate solutions were prepared.
h e solution of the titanium and niobium tartarate complexes, which
are not commercially available, were prepared in the laboratory from its
hydrated oxide (Nb
2
O
5
n
H
2
O and TiO
2
n
H
2
O); the details of the prepara-
tion process are discussed elsewhere [94]. In the second step, stoichiomet-
ric amounts of titanium tartarate (100mL; 0.2545 gL
-1
), niobium tartarate
(1.72mL; 0.2167 gL
-1
), ferric nitrate (0.088 g, 0.21 mmol) with triethanol-
amine (3mL) and 20 mL of absolute ethanol solutions were taken in a bea-
ker as per the predetermined chemical compositions (example shown for
x = 0.01) with constant stirring for 30 min at room temperature. h en the
mixture was adjusted to a pH of 9.0 with 6M NaOH solution, and stirred
for 30 min, yielding a stable light yellow homogeneous emulsion. h e
resulting mixture was transferred into a 100 mL Tel on-lined stainless steel
autoclave and heated to 150
°
C for 22 h under auto-generated pressure. h e
reaction mixture was allowed to cool to room temperature and the pre-
cipitate was i ltered, washed with distilled water i ve times, and dried in
a vacuum oven at 100
°
C for 15 h. For comparison, the same method was
used to synthesize Fe-TiO
2
, Nb-TiO
2
and pure TiO
2
.
°
15.3.1 Photocatalytic Reactor
h e photocatalytic experiment was carried out in a simple cubic photo-
reactor as depicted in Figure 15.6. h ere was a 400 W ultrahigh-pressure
Hg-lamp (PHILIPS-HPL-N, G / 74 / 2, MBF-400) with a primary wave-
length distribution approximately (λ > 280 nm) attached inside the photo-
reactor. An air circulating exhaust fan was attached to the backside of the
cubic reactor to remove the hot air inside the reactor. h e upper portion of
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