Co-doped ZnS with large adsorption capacity for recovering Hg0 from non-ferrous metal smelting gas as a co-benefit of electrostatic demisters.

The installation of electrostatic demisters (ESDs) makes possible the use of sorbent injection technology for recovering Hg0 from non-ferrous smelting gas. ZnS, as a typical smelting raw material, could be a promising candidate due to the sulfur boding site for mercury. However, the low reaction rate and poor adsorption capacity limited its application. In this study, Co was incorporated into ZnS to enhance adsorption activity for recovering Hg0. Co0.2Zn0.8S exhibited the best Hg0 capture performance among the modified sorbents. The Hg0 adsorption capacity was up to 46.01 mg/g at 50 °C (with 50% breakthrough threshold), and the adsorption rate was as high as 0.017 mg/(g min). Meanwhile, SO2 and H2O had no poison effects on Hg0 adsorption. The chemical adsorption mechanism was proposed, which was Co3+, and sulfur active sites could immobilize Hg0 in the form of stable HgS, following a Mars-Maessen reaction pathway. The spent sorbent will release ultrahigh concentration mercury-containing vapor through the heating treatment, which facilitated centralized recovery of Hg0. Meanwhile, inactivated sorbent can be used as smelting raw material to recover sulfur resources. Therefore, the control of Hg0 emission from non-ferrous smelting gas by Co-adopted ZnS was cost-effective and did not form secondary pollution. Graphical abstract.