Roles of Sulfuric Acid
in Elemental Mercury Removal
by Activated Carbon and Sulfur-Impregnated Activated Carbon
Eric A. Morris
Donald W. Kirk
Charles Q. Jia
Kazuki Morita
10.1021/es301209t.s001
https://acs.figshare.com/articles/journal_contribution/Roles_of_Sulfuric_Acid_in_Elemental_Mercury_Removal_by_Activated_Carbon_and_Sulfur_Impregnated_Activated_Carbon/2504845
This work addresses the discrepancy in the literature
regarding
the effects of sulfuric acid (H<sub>2</sub>SO<sub>4</sub>) on elemental
Hg uptake by activated carbon (AC). H<sub>2</sub>SO<sub>4</sub> in
AC substantially increased Hg uptake by absorption particularly in
the presence of oxygen. Hg uptake increased with acid amount and temperature
exceeding 500 mg-Hg/g-AC after 3 days at 200 °C with AC treated
with 20% H<sub>2</sub>SO<sub>4</sub>. In the absence of other strong
oxidizers, oxygen was able to oxidize Hg. Upon oxidation, Hg was more
readily soluble in the acid, greatly enhancing its uptake by acid-treated
AC. Without O<sub>2</sub>, S(VI) in H<sub>2</sub>SO<sub>4</sub> was
able to oxidize Hg, thus making it soluble in H<sub>2</sub>SO<sub>4</sub>. Consequently, the presence of a bulk H<sub>2</sub>SO<sub>4</sub> phase within AC pores resulted in an orders of magnitude
increase in Hg uptake capacity. However, the bulk H<sub>2</sub>SO<sub>4</sub> phase lowered the AC pore volume and could block the access
to the active surface sites and potentially hinder Hg uptake kinetics.
AC treated with SO<sub>2</sub> at 700 °C exhibited a much faster
rate of Hg uptake attributed to sulfur functional groups enhancing
adsorption kinetics. SO<sub>2</sub>-treated carbon maintained its
fast uptake kinetics even after impregnation by 20% H<sub>2</sub>SO<sub>4</sub>.
2012-07-17 00:00:00
oxidize Hg
Hg uptake capacity
Hg uptake kinetics
Elemental Mercury Removal
Hg uptake
H 2SO
bulk H 2SO phase
AC pore volume