Review of elemental mercury (Hg0) removal by CuO-based materials
Dong Ye, Xiaoxiang Wang, Run-xian Wang, Xin Liu, Hui Liu, Haining Wang
Abstract
Mercury emission has become a great environmental concern because of its high toxicity, bioaccumulation, and persistence. Adsorption is an effective method to remove Hg0 from coal-fired flue gas, with adsorbents playing a dominant role. Extensive investigations have been conducted on the use of CuO-based materials for Hg0 removal, and some fruitful results have been obtained. In this review, we summarize advances in the application of CuO-based materials for Hg0 capture. Firstly, the fundamentals of CuO, including its crystal information and synthesis methods, are introduced. Then, the Hg0 removal capability of some typical CuO-based adsorbents is discussed. Considering that coal-fired flue gas also contains a certain amount of NO, SO2, H2O, NH3, and HCl, the impacts of these species on adsorbent Hg0 removal efficiency are summarized next. By generalizing the mechanisms dominating the Hg0 removal process, the rate-determining step and the key intermediates can be discovered. Apart from Hg0, some other air pollutants, such as CO, NOx, and volatile organic compounds (VOCs), account for a certain portion of flue gas. In view of their similar abatement mechanisms, simultaneous removal of Hg0 and other air pollutants has become a hot topic in the environmental field. Considering the Hg0 re-emission phenomena in wet flue gas desulfurization (WFGD), mercury capture performance under different conditions in this device is discussed. Finally, we conclude that new adsorbents suitable for long-term operation in coal-fired flue gas should be developed to realize the effective reduction of mercury emissions.