In-situ preparation of zinc sulfide adsorbent using local materials for elemental mercury immobilization and recovery from zinc smelting flue gas

Abstract Exploiting a cheap and readily available adsorbent for elemental mercury (Hg0) immobilization from zinc smelting flue gas has become an urgent requirement to ensure the sustainable development of zinc smelting industry. Herein, a novel protocol of using intermediate products derived from zinc smelting process to synthesize porous ZnS adsorbent is proposed in this study to provide a practicable support for efficient capture of Hg0. The as-prepared ZnS-300℃-120 min adsorbent exhibits an outstanding performance for Hg0 capture. Approximately 100% of Hg0 can be entrapped even under the extreme conditions of high gaseous hourly space velocity (GHSV) values and wide temperature ranges. Additionally, its saturated adsorption capacity and average adsorption rate reach 3.6 mg/g and 1.3 μg/g/min, respectively, much higher than common adsorbents. The in-situ Raman spectra and XPS spectra results confirm that the unsaturated short-chain Sn2- is dominant adsorption site. The active Sn2- site would be formed on the surface of ZnS during the calcination process. The formed Sn2- ligand would promptly and selectively react with Hg0 to form stable HgS, consequently achieving the efficient immobilization of Hg0. After Hg0 capture, the spent ZnS adsorbent can be safely disposal of by thermal desorption, simultaneously realizing the recycling of zinc and mercury resource. The purposefully synthesized ZnS adsorbent can provide a practical and yet easy-to-adopt strategy for mercury pollution control of zinc smelting industry, while opening a new path to recycle valuable metal from smelting waste.