Removal of gaseous elemental mercury using seaweed chars impregnated by NH4Cl and NH4Br

Enteromorpha is a kind of waste algae that can cause marine ecological disaster. Actively exploring some effective ways for resource utilization of Enteromorpha has important economic and environmental significance. In this article, NH4CI and NH4Br modified Enteromorpha chars (E8C5 and E8B5) were prepared by pyrolysis and simple impregnation method for capturing gas phase elemental mercury (Hg) for the first time. The effects of pyrolysis temperature, loading value, reaction temperature and concentrations of main flue gas components (e.g. O-2, NO, SO2, H2O) on Hg capture were studied. Mercury removal mechanism and kinetics were also investigated. The results show that Hg removal efficiency increases with the increase of pyrolysis temperature, and the optimal pyrolysis temperature is 800 'C. Hg removal is significantly enhanced by NH4CI or NH4Br modification, and the chars modified by NH4Br show better performance than those modified by NH4CI. Optimal loading values and reaction temperature for E8C5 and E8B5 are 5 wt.% and 130 degrees C, respectively. Presence of O-2 and NO promotes Hg removal, whereas presence of SO2 inhibits Hg removal. Lower concentration of H2O is beneficial to Hg removal, but higher concentration of H2O shows an obvious inhibitory effect on Hg capture. Hg adsorption over E8C5 and E8B5 are endothermic processes. Chemisorption plays a key role in Hg removal. Both Hg removal processes over E8C5 and E8B5 meet pseudo-second-order kinetic model. (C) 2019 Elsevier Ltd. All rights reserved.