Activated coke impregnated with cerium chloride used for elemental mercury removal from simulated flue gas

Gas-phase elemental mercury (Hg0) removal by activated coke impregnated with cerium chloride (AICC) was studied under simulated flue gas conditions. Brunauer–Emmett–Teller (BET), X-ray diffractogram (XRD), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the samples. The effects of CeCl3 loading values, reaction temperatures and individual flue gas components including O2, NO, SO2 and H2O (g) on Hg0 removal efficiency of AICC samples were investigated. Results showed that Hg0 removal efficiency of AC was significantly enhanced by CeCl3. The optimal CeCl3 loading value and reaction temperature was around 6% and 170 °C, respectively. Additionally, the experiment results of effects of flue gas components on Hg0 removal efficiencies showed that when O2 was present in the flue gas, NO and SO2 were observed to promote Hg0 oxidation. However, in the absence of O2, SO2 showed an insignificant inhibition on Hg0 removal. Furthermore, when H2O was added into the flue gas, the Hg0 removal capacity had a slight declination. The analyses of XRD and XPS showed that CexOy and C–Cl were generated on the surface of AICC and those active elements had remarkably positive effects on the Hg0 removal. The reaction mechanism indicated that Hg0 oxidation was achieved through two pathways: one was that Hg0 bond with CeO2 and was converted by the catalytic oxidation of valence variable cerium; the other was that Hg0 reacted with C–Cl on the sample and was oxidized favored by chloride presence. And according to Hg 4f XPS analysis, the mercury on the surface of AICC was mainly in the form of mercuric oxide (HgO) and mercuric chloride (HgCl2).

► AICC was developed for effective Hg0 removal from simulated flue gas.
► The AICC samples possessed a joint oxidation effect on Hg0 removal.
► The Hg species adsorbed on AICC samples were identified mainly as HgO and HgCl2.
► The roles of O2, NO, SO2 and H2O (g) in Hg0 oxidation by AICC were explored.