Analysis of solid sorbents for control and removal processes for elemental mercury from gas streams:a review

Due to the restriction such as the Minamata Convention as well as the IED of the European Commission,mercury removal from flue gases of coal-fired power plants(CPP)is an increasingly important environmental issue.This makes this topic very crucial for both the energy industry and scientists.This paper shows how mercury arises from natural resources,i.e.,coals,through their combustion processes in CPP and considers the issue of mercury content in flue gases and solid-state coal combustion by-products.The main part of this paper presents a review of the solid sorbents available for elemental mercury control and removal processes,tested on a laboratory scale.The described solutions have a potential for wider usage in exhaust gas treatment processes in the energy production sector.These solutions represent the latest developments in the field of elemental mercury removal from gases.The authors present an overview of the wide range of solid sorbents and their modifications intended to increase affinity for Hg^(0).Among the presented sorbents are the wellknown activated carbon solutions but also novel modifications to these and other innovative sorbent proposals based on,e.g.,zeolites,biochars,other carbon-based materials,metal-organic frameworks.The paper presents a wide range of characteristics of the described sorbents,as well as the conditions for the Hg^(0) removal experiments summarizing the compendium of novel solid sorbent solutions dedicated to the removal of elemental mercury from gases.

New insights into mercury removal mechanism on CeO2- based catalysts： A first-principles study

First-principles calculanons were performed to investigate the mechamsm of Hg0 adsorpnon and oxidation on CeO2（111）. Surface oxygen acnvated by the reducnon of Ce to Ce a vlta to Hg~ adsorption and oxidation processes. Hg0 was fully oxidized by the surface lattice oxygen on CeO2（111）, without using any other oxidizing agents. HCI could dissociate and react with the Hg adatom on CeO2（111） to form adsorbed Hg CI or CI-Hg-Cl groups, which promoted the desorption of oxidized Hg and prevented CeO2 catalyst deactivation. In contrast, O-H and H-O-H groups formed during HC1 adsorption consumed the active surface oxygen and prohibited Hg oxidation. The consumed surface oxygen was replenished by adding O2 into the flue gas. We proposed that oxidized Hg desorption and maintenance of sufficient active surface oxygen were the rate-determining steps of Hg0 removal on CeO2-based catalysts. We believe that our thorough understanding and new insights into the mechanism of the Hg0 removal process will help provide guidelines for developing novel CeO2-based catalysts and enhance the Hg removal efficiency.

MoS_(2) quantum dots based MoS_(2)/HKUST-1 composites for the highly efficient catalytic oxidation of elementary mercury

Due to the ever-tightening regulation on mercury emission in recent decades,there is an urgent need to develop novel materials for the removal of elemental mercury at coal-fired power plants.In this study,a series of MoS_(2) quantum dots(QDs)-based MoS_(2)/HKUST-1 composite materials were prepared.It is found that MoS_(2)QDs were encapsulated by HKUST-1and enhanced the crystallinity and specific surface area of HKUST-1.The MoS_(2)/HKUST-1 showed excellent performance in catalytic oxidation of Hg~0as compared with pristine HKUST-1.It is found that surface layer of lattice oxygens is active and participates in Hg^(0) oxidation,while the consumption of surface oxygens then leads to the formation of oxygen vacancies on the surface.These vacancies are effective in the adsorption and dissociation of O_(2),which subsequently participates in the oxidation of Hg^(0).Moreover,the study on the influence of commonly seen gas components,such as SO_(2),NO,NH_(3) and H_(2)O,etc.,on Hg^(0) oxidation demonstrated that synergistic effects exist among these gas species.It is found that the presence of NO promotes the oxidation of Hg^(0) using oxygen as the oxidant.