Environmental Engineering Reference
In-Depth Information
The TCLP test was carried out on untreated AC, MnO
2
-impregnated AC, and
FeCl
3
-impregnated AC. The textural characteristics of AC are provided in Table
5.12. Leaching results are summarized in Table 5.13. The calculated maximum
mercury indicated the maximum concentration that was reached if all of the mer-
cury had dissolved during leaching; it also represented the worst-case scenario.
Only MnO
2
-impregnated AC was detected in the leachate at 0.31 μg/L for adsorbed
original Hg
0
and 0.41 μg/L for adsorbed original Hg
2+
. The content of mercury in
the leachate was much lower than the 0.025 mg/L TCLP limit. The mercury ap-
peared to be very stable in the three ACs with respect to leaching.
Table 5.12
Textural characteristics of activated carbon
Specific
surface area
(m
2
/g)
Bulk specific
weight
(g/cm
3
)
Pore
volume
(cm
3
/g)
Micropore
volume
(<20 Å) (cm
3
/g)
Activated
carbon
Particle size
(mm)
Porosity
(%)
AC(MZ)
1850
0.35
1.05
0.35
0.09
67
AC(MnO
2
-MZ)
865
0.41
0.29
0.10
0.09
45
AC(FeCl
3
-MZ)
1470
0.38
0.92
0.31
0.09
58
Table 5.13
TCLP leaching results
Type of
mercury
a
Bulk
(μg/g)
Calc. Max.
(μg/L)
Leaching result
(μg/L)
Type of sample
Hg
0
BDL
b
0.63
31.4
AC(MZ)
Hg
2+
0.22
10.9
BDL
Hg
0
0.51
25.6
0.31
AC(MnO
2
-MZ)
Hg
2+
0.21
10.5
0.41
Hg
0
0.57 28.7 BDL
Hg
2+
0.18 8.8 BDL
a
The original type of mercury in simulated flue gas;
b
Below detection limit (Hg < 0.01 μg/L)
AC(FeCl
3
-MZ)
5.5.2.2 Mercury Stability in Activated Carbon Sorbents with Column Tests
Various laboratory leaching methods have been developed, including batch tests,
column tests, serial and sequential leaching tests, etc. Five different kinds of
leaching liquids were used in the column tests to simulate various disposal solution
environments. These kinds of liquids included deionized water, 1% sulfuric acid
solution (1% H
2
SO
4
), 1% ferric trichloride solution (1% FeCl
3
), 1% sodium car-
bonate solution (1% Na
2
CO
3
), and 1% sodium hydroxide solution (1% NaOH). The
flow of the leaching liquid was controlled at about 5 ml/h, after which the leachate
was collected every day for analysis.
The Hg content of each AC, which was used in the stability test, was adjusted to
about (52±1) μg/g through the Hg adsorption experiment system. Figs. 5.35 to 5.37
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