ZnS
is a promising sorbent in recovering Hg0 from industrial
flue gas due to its excellent Hg0 adsorption capacity.
However, the internal structure–activity relationship still
needs to be further clarified. In this work, ZnS sorbents with different
structures were synthesized with the hydrothermal method by tuning
the temperature. The samples had significant differences in the crystallinity,
morphology, particle size, and sulfur (S) active sites. The results
indicated that Hg0 removal performance was determined by
the specific surface area and S active sites. ZnS synthesized at low
temperatures (80-ZnS and 120-ZnS) had a larger surface area, while
the S sites on the high-temperature-synthesized sample (160-ZnS) were
more active for Hg0 adsorption. The 160-ZnS sample exhibited
a much higher Hg0 adsorption amount per unit surface area.
Further characterization revealed that S2
2– and S
x
were the main active sites for
Hg0 adsorption. S
x
existed
in the form of long-chain polysulfur (L-S
x
) on 80-ZnS and 120-ZnS, while it exhibited in the form of short-chain
polysulfur (S-S
x
) on 160-ZnS. L-S
x
had negligible adsorption ability, while S-S
x
had a high affinity for Hg0. Hg0 can react with S2
2– and S-S
x
, forming α-HgS and β-HgS, respectively.
The new insight in this work can provide theoretical guidance for
the design and structure optimization of ZnS, facilitating its practical
industrial application.