Civil Engineering Reference
In-Depth Information
10
200
NO
2
-
NH
4
+
NO
2
-
Pd
Pd
160
8
N
2
O
N
2
6
120
PdCu
Pd
Pd
NO
3
-
NO
2
-
NO
N
2
OH
-
80
4
Pd
NH
4
+
40
2
OH
-
0
0
0
20
40
60 80
Time (min)
100
120
140
160
(
a
)
(
b
)
Figure 17.9
(a) Catalytic conversion of nitrate to nitrogen and ammonia via nitrite. (b) Degradation of
nitrates using Pd-BC composite catalyst with concomitant evolution of nitrite and ammonium ions with
reaction time .
PdBC COATED ROTATING
ACRYLIC DISCS MOUNTED ON
A SHAFT
VENT FOR H
2
MAGNETIC DRIVE
MECHANISM
AQUEOUS PHASE
WITH PCP
PURGING WITH H
2
Figure 17.10
Schematic of rotating catalyst contact reactor used for synthesis, immobilization,
and palladization of bacterial cellulose and for catalytic dechlorination of PCP by Pd-BC composite.
5 to 6 hours. h e white BC turns black due to palladization, indicating the formation of
Pd nanoparticles in the BC network. h is Pd-BC composite was investigated for its cata-
lytic ei cacy of dechlorination both as a batch process as well as a continuous process at
atmospheric pressure and room temperature in the same reactor vessel. Dechlorination
of PCP into phenol and HCl takes place due to reduction by active hydrogen present on
the surface of Pd nanoparticles. h e dechlorination reaction is written as:
C
6
H
6
OHCl
5
(PCP) + Pd
x
H
y
(palladium hydride) → C
6
H
6
OH (phenol) + xPd
0
+ 5HCl
In the case of batch experiment, PCP concentration decreases to < 25% within 40
min and goes to near completion at er ~2 hours (Figure 17.11a). Although dechlo-
rination results in the formation of HCl, the catalytic activity of 'Pd' was found to be
retained. For continuous l ow dechlorination, two dif erent l ow rates, 5.5 mLmin
-1
and
11 mLmin
-1
, were used with a hydraulic retention time of 2 and 1 hours respectively.
It was found that catalytic degradation of PCP decreases with increasing l ow rate or
decreasing hydraulic retention time (Figure 17.11b).
Nanoparticles of TiO
2
are known to be photocatalytic, and hence Sun
et al.
syn-
thesized TiO
2
nanoparticles supported into BC matrix [27]. h ese nanoparticles were
