A review on removal of elemental mercury from flue gas using advanced oxidation process: Chemistry and process

Abstract

Mercury emission from combustion sources has become a great public concern due to its hazards for human health and ecosystem. Although a large number of Hg0 removal technologies already have been developed, none of them can obtain large-scale applications due to various technical and economic issues. Therefore, more efforts are needed to develop cost-effective Hg0 removal technologies. Advanced oxidation technologies (AOTs) are defined as those technologies that can generate mainly the hydroxyl radical (OH) with high oxidation potential and other reactive oxygen species including superoxide anion radical (O2−), hydrogen peroxide (H2O2) and singlet oxygen, by various environmentally benign physical or chemical processes. In the past two decades, AOTs have gained an extensive attention research and successful applications in water treatment and soil remediation, as well as in flue gas purification for multipollutant treatment. In recent years, an increasing attention has been paid to the removal of Hg0 in flue gas using AOTs due to the excellent prospects of this technology. To date, the four main AOTs for removing Hg0 in flue gas include plasma AOTs, TiO2 photocatalytic AOTs, photochemical AOTs and activated oxidant AOTs. While these AOTs have shown excellent prospects for removing Hg0 in flue gas, a number of technical issues need to be resolved before they are amenable to industrial applications. This article provides the first comprehensive review of the progress and recent developments of these four AOTs for removing Hg0 in flue gas, with emphasis on the chemistry and processes involved. The effects of the main flue gas components and process parameters on Hg0 removal using these AOTs are summarized. The reaction products, mechanism, kinetics, reactor types and process flow systems, and impacts on of Hg0 removal are also comprehensively reviewed, with insights into the challenges for large-scale applications. This review is intended to advance our understanding and outline directions for future developments of this research field.