Fe and Co modified vanadium-titanium steel slag as sorbents for elemental mercury adsorption

Iron and cobalt modified vanadium titanium steel slag (VTSS) adsorbents Fe(x)-Co(y)/VTSS (with different Fe/Co molar ratios of x/y) prepared by an impregnation method were employed to remove elemental mercury (Hg-0) from simulated flue gas in a wide-temperature window (150-300 degrees C). The samples were characterized by XRD, BET, HRTEM, EDS and H-2-TPR. The effects of iron to cobalt molar ratios of x/y, capture temperature, and flue gas components (such as O-2, SO2 and H2O) on the Hg-0 adsorption efficiency were evaluated. The Hg-0 adsorption mechanisms were proposed by XPS, TG and the pseudo-second-order kinetic model. The results showed that the increase of cobalt amount and the cooperation of Fe and Co promoted Hg-0 capture. The Fe(3)-Co(3)/VTSS adsorbent exhibited the highest Hg-0 removal efficiencies of 77.4% within 600 min in 6 vol% O-2 at 300 degrees C. The presence of O-2 promoted Hg-0 adsorption. The influence of SO2 on the Hg-0 removal efficiency was weak, while the addition of 8 vol% H2O and 500 ppm SO2 was found to have a serious inhibition effect. The XPS and TG results showed that the HgO was the major species in the captured mercury, which illustrated that Hg-0 removal over Fe(x)-Co(y)/VTSS was a catalytic oxidation process. The pseudo-second-order model was demonstrated to simulate the removal of Hg-0 by Fe(x)-Co(y)/VTSS and the adsorption process is controlled by chemisorption.