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Study of the Effect of Adsorption Temperature on Elemental Mercury Removal Performance of Iron-Based Modified Biochar
journal contribution
posted on 2019-11-12, 22:13 authored by Rui Zhao, Li Jia, Yu-xing Yao, Rui-peng Huo, Xiao-lei Qiao, Bao-guo FanAn iron-based modified biochar was
prepared by the coprecipitation
method, including single iron-based modified biochar with FeCl3 and iron-based biochar doped with Cu and Mn from CuSO4 and KMnO4. Combined with the physicochemical properties
of sorbents, the effect of flue gas temperature on the mercury adsorption
performance of the sorbents was explored within the temperature range
of 50–350 °C. The adsorption mechanism was further explored
by adsorption kinetics, thermodynamics, and temperature-programmed
desorption (TPD) analyses. The results showed that the mercury adsorption
capacity of unmodified biochar decreased monotonously with temperature,
but the adsorption capacities of Fe/BC, FeCu/BC, and FeMn/BC all enhanced
first and then weakened, with 200 °C being the optimum adsorption
temperature. FeCu/BC had the strongest adsorption capacity, while
Fe/BC had the worst one. CO and COOH, metal oxides and ions,
lattice oxygen, chemisorbed oxygen, and Cl ions were all active sites
for oxidative adsorption of Hg0, among which Fe2O3 and CuO or CuFe2O4 exerted a
synergistic effect. Excessive temperature caused destruction to the
porous structure and deactivation of the active centers, leading to
the reduction of physisorption and chemisorption. Mercury adsorption
on sorbents needs more activated energy due to the enhancement of
chemisorption, and the moderate increase of temperature contributed
to the adsorption properties of the sorbents. The Hg0 adsorption
on modified biochar was spontaneous and endothermic, and the complexity
degree of the adsorption process was promoted. TPD results showed
that at 200 °C the removal of Hg0 by modified biochar
was mainly strong chemisorption and that HgO was mainly formed.