Environmental Engineering Reference
In-Depth Information
90
Unloading (+0.5 V)
60
30
CI
0
CH
3
N
+
CH
N
CH
3
S
H
3
C
-30
N
-60
Loading (+0.0 V)
-90
0
200
400
600
800
1000
1200
Time (s)
FIGURE 2.19
Time proile of methylene blue concentration (monitored by spectophotometry at 430 nm) during loading (0.0 V
vs. SCE) and unloading (0.9 V vs. SCE) of dye inside porous carbon (NpC-CTAB).
50
Without arsenic
With arsenic
40
30
20
10
0
-10
-20
0.4
0.6
0.8
1.0
Electrode potential (V vs. Ag/AgCl)
FIGURE 2.20
Cyclic voltammetry of a porous carbon electrode (2PSC) modiied with CoOx nanoparticles in the absence
(dashed line) and presence (full line) of
AsO
3
−
(187.5 ppm) ions. Electrolyte = 0.1 M phosphate buffer (pH = 7).
Scan rate = 5 mV/s.
−
3
−
3
−
2
CoOOH
+
AsOHO
+
2
→
2
oOH
(
)
+
sO
+
2
OH
(IV)
3
2
2
4
It is likely that reaction IV occurs with the anion adsorbed in the nanoparticle surface.
The small (<20 nm) metal oxide nanoparticles have a large surface area where such adsorp-
tion can occur. As it can be seen, low levels (<200 ppm) of arsenic can be easily detected
using CV on modiied 2PSC. Iron oxides can also be used to detect arsenic [155].
