Environmental Engineering Reference
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Fig. 5.22 AC(MZ-T) Hg 0 adsorption in the N 2 environment
According to the experimental results of the Hg 0 adsorptions in the N 2 envi-
ronment of four kinds of commercial ACs, as well as the discussion on the influence
of surface physical characteristics and surface chemical characteristics on the ad-
sorption, it can be concluded that the Hg 0 adsorption by AC was a chemical ad-
sorption process in the N 2 environment. The Hg 0 was possibly oxidized to HgCl 2 or
HgS by Cl or S during the adsorption process of AC(MZ).
Understanding the adsorption mechanism of Hg 0 by AC is valuable for im-
proving Hg 0 adsorption capability of the sorbent, which is necessary for increasing
mercury emission control efficiency in AC injection technology. In this paper, the
key focus was to understand the mechanism. Accordingly, the adsorption experi-
ment was carried out primarily in order to study the influence of physical and
chemical adsorptions in the process of AC adsorbing Hg 0 in the N 2 environment.
The experimental results showed that AC(XK), AC(YK) and AC(MJ), which were
all prepared by steam activation with relatively clean surfaces, had no adsorption
capability of Hg 0 in the N 2 environment. However, the AC(MZ) that was prepared
using a chemical activation method with ZnCl 2 showed high Hg 0 adsorption capa-
bility in the same experimental condition. Using the high temperature treatment
system, AC(MZ) was modified to remove SFGs and was renamed AC(MZ-T). The
AC(MZ-T) showed no Hg 0 adsorption capability in the N 2 environment.
Based on the adsorption experimental results of AC(XK), AC(YK), AC(MJ),
AC(MZ) and AC(MZ-T), as well as the surface analysis of its physical and
chemical characteristics, the Hg 0 adsorption by AC was a chemical adsorption
process in the N 2 environment. Hg 0 was likely to be oxidized and retained by the
oxidative elements produced on the AC surface through chemical activation.
Without the oxidative elements capable of oxidizing Hg 0 , AC was unable to adsorb
Hg 0 in the N 2 environment through physical adsorption.
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