Elemental mercury capture from industrial gas emissions using sulfides and selenides: a review

Abstract

Mercury emission from industrial activities has become a major environmental health concern, because mercury is one of the most toxic metals encountered in the environment. Elemental mercury is the dominant Hg species in gas streams. Adsorption is regarded as a practical technique for Hg0 removal, for which developing efficient and economic adsorbents are needed. Chalcogenides have recently gained increasing research interest owing to their high binding affinity for Hg0. Chalcogen-based adsorbents include S-modified adsorbents, H2S- and SO2-activated adsorbents, polysulfide chalcogels, mineral sulfides and metal selenides. This article reviews chalcogen-based adsorbents for Hg0 capture from gas streams, with focus on removal performances, mechanisms, advantages and disadvantages. Results show that S modification, and H2S and SO2 activation generate a great variety of active sulfur species on the adsorbent surface, resulting in enhanced Hg0 removal activity. Sulfur species include elemental sulfur, sulfide, thiophene and sulfate. Nonetheless, removal efficiency decreases to some extent due to the presence of acidic flue gas components and steam. On the other hand, mineral sulfides and metal selenides exhibit outstanding Hg0 removal performances with fast adsorption rate, high mercury capacity and excellent resistance to SO2 and H2O. Yet most mineral sulfides and metal selenides perform well below 100 °C, which might limit industrial applications.