*3.1. Physicochemical Properties of Sorbents*

The physical and chemical properties of the three test sorbents, AC, SAC, and FeS, were summarized in Table 1. Because FeS is a non-porous mineral, its surface area and pore volume were much smaller than those of AC and SAC. Elemental analyses of AC and SAC showed that the oxygen and sulfur contents in SAC were increased after impregnation of sulfur on AC, hence SAC should be more favored for Hg2<sup>+</sup> uptake because sulfur-containing groups on SAC had high affinity towards mercuric sulfide formation. The oxygenated groups are also known beneficial for Hg adsorption. The increase in the oxygen content after sulfur impregnation could be due to the reaction of S with C to form vaporized CS2 evolved from the SAC surface.


**Table 1.** The physicochemical properties of sorbents.

\* SBET: specific BET surface area; SMicro: micropore area; VTotal: total pore volume; Vmicro: micropore volume.
