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

Transition metal elements doping is a conventional strategy for the modification of sulfide-based sorbents to obtain preferable Hg-0 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 (K-sp) 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 Hg-0 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 Hg-0 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 Hg-0 from Hg-0-rich flue gas.