Mercury Control and Mercury Stability in Byproducts - Mercury Emission and its Control in Chinese Coal-Fired Power Plants - page 140

show the leaching results of AC(MZ), AC(MnO 2 -MZ), and AC(FeCl 3 -MZ) using
five different leaching liquids continuously for 14 days and with the standard TCLP.
The average Hg concentration in 1% NaOH leachate (pH>14) was about 0.89 μg/L,
which was close to the average Hg concentration of about 0.78 μg/L in 1% H 2 SO 4
leachate (pH<1) (Fig. 5.35). However, this value was much higher than the average
Hg concentrations in H 2 O, 1% FeCl 3 , and 1% Na 2 CO 3 leachates (3<pH<10), which
mostly ranged from 0.22 to 0.28 μg/L. It seemed that Hg was easily released from
the surface of the AC(MZ) in a strong alkaline or acid solution. Compared with the
Hg concentration of the TCLP leachate, which was about 0.73 μg/L, the Hg con-
centrations in all the leachates were still lower than the safe limit defined by the
Universal Treatment Standard, which limits content of mercury in the TCLP
leachate to 25 μg /L. Based on these experiments, Hg was found to be stable on the
surface of the AC(MZ) in the solution.

1.0

BLC Leaching

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

H 2 OH 2 SO 4 FeCl 3 Na 2 CO 3 NaOH TCLP

Different leaching methods

Fig. 5.35 The leaching results of AC(MZ)

90

MnO 2 -AC Leaching

80

70

60

50

40

30

20

10

0

H 2 OH 2 SO 4 FeCl 3 Na 2 CO 3 NaOH TCLP

Fig. 5.36 The leaching results of AC(MnO 2 -MZ)

Different leaching methods