Stepwise Ions Incorporation Method for Continuously Activating PbS to Recover Mercury from Hg0-Rich Flue Gas.

ABSTRACT

Transition metal elements doping is a conventional strategy for the modification of sulfide-based sorbents to obtain preferable Hg0 adsorption capability. One problem was that such a method could only obtain a temporary promotion to sulfides. To achieve continuous promotion of mercury capture performance, we use the difference of solubility product (Ksp) between sulfides to develop a postsynthesis approach for stepwise doping of PbS by Cu2+ ions. Moreover, it further demonstrated the restoration of PbS surface under a given high temperature, enabled by thermal migration of the foreign Cu2+ ions from outer to interlayer in PbS lattice and rereleased of S sites occupied previously by mercury. The Hg0 adsorption capacity of PbS was enlarged from 0.86 to 2.76 mg·g-1 after the first doping, resulting from the mild oxidization of S2- to S- in the surface layer by foreign Cu2+ ions. Furthermore, regeneration of spent PbS can be implemented by stepwise Cu2+ incorporation due to the renewability of the surface, enabling even better Hg0 adsorption capacity after six cycle tests. This stepwise incorporation method promises the precise utilization of doped elements, as well as offers a tutorial example for the activation and regeneration of sulfide sorbents to recover Hg0 from Hg0-rich flue gas.