Heterogeneous Reaction Mechanisms and Functional Materials for Elemental Mercury Removal from Industrial Flue Gas

Gaseous elemental mercury (Hg-0) is of increasing concern in industrial flue gases because of its difficult disposal. Currently, catalysis conversion and adsorption to oxidized species (Hg2+) and particle-bonded states (Hg-P) are two common Hg-0 disposal methods. While no clear boundary exists between these methods, the selection of technologies for practical applications highly depends on the gas temperature, mercury concentration, and gas components over a solid material. This review aims to describe some principles for solid material selection, discusses the heterogeneous reaction mechanisms for gaseous Hg-0 conversion, classifies the various types of catalysts and sorbents, and summarizes their potential applications. Gaseous Hg-0 undergoes interface physical adsorption, catalytic oxidation, and chemical adsorption processes. Overcoming the surface bonding energies can convert the Hg-0 to Hg2+ via the catalytic process. Meanwhile, strong bonding energies can ensure chemical adsorption, resulting in mercury surface solidification. On this basis, the catalysts and sorbents materials, the reaction mechanism, and different types of solid materials were evaluated. We clearly discussed the reaction mechanism over different type of functional materials for Hg-0 removal, to provide recommendations for studies to address concerns regarding laboratory-scale to full-scale applications. Moreover, some key parameters and a basic understanding of the practical applications were proposed.

Automated summary

This study discusses the principles and applications of solid materials in the treatment of gaseous mercury, including processes such as catalytic oxidation, physical adsorption, and chemical adsorption. Overcoming surface bonding energies can convert Hg-0 to Hg2+ via a catalytic process, while strong bonding energies ensure chemical adsorption and solidify mercury on the surface.