In situ activation synthesis of tire-derived sorbents for efficient immobilization of elemental mercury from flue gas

Mercury removal from coal combustion flue gas remains a daunting challenge because of the lack of cost-effective sorbents. In this study, the in situ activation synthesis of tire chars was realized through SO2 induction and the tire-derived sorbents were used for elemental mercury (Hg-0) removal from the simulated flue gas. Therein the sulfur species in tire chars are regulated. The results indicated that the specific surface area of tire chars was slightly decreased whereas more micropores were generated after SO2 activation. Compared with raw tire char, the sulfur content of tire-derived sorbents was obviously increased. The tire-derived sorbents also contained more sulfur-and oxygen-containing functional groups. For this reason, the Hg-0 removal performance of tire-derived sorbents was dramatically increased after SO2 activation. The optimum pyrolysis temperature for the synthesis of tire-derived sorbents was 600 degrees C. The SO2 concentration in activation atmosphere had little effect on the Hg-0 removal performance of tire-derived sorbents. The presence of SO2, NO and O-2 was beneficial for Hg-0 removal H2O had little effect on Hg-0 removal. The Hg-0 adsorption capacity of tire-derived sorbents was further compared with the previously reported sorbents through adsorption dynamic simulations. Furthermore, the mechanism of Hg-0 removal over tire-derived sorbents was revealed through XPS analysis and mercury temperature programmed desorption. It was found that the Hg-0 removal process was mainly dominated by che-isorption, where organic sulfur species, C--O group and COOH/C(O)-O-C group served as active sites for Hg-0 capture.