Enhanced mercury adsorption capacity by sulfurization of activated carbon with SO2 in a bubbling fluidized bed reactor

Sulfur impregnation of activated carbon (AC) with the gas stream containing 4% (v/v) sulfur dioxide in nitrogen was performed in a bubbling fluidized bed furnace. Sulfurization at 700 °C for 1 h resulted in the Hg selective adsorbent, containing 11 wt.% sulfur, with the mercury adsorption capacity of 50% higher than AC. The surface area loss of the AC during the sulfurization was only about 9% leading to a little decrease in the initial sorption rate. The sulfur functionalities in the organic (83%) and oxidized (17%) forms were found as the responsible sites for Hg adsorption increasing. Using HNO3 as the extractant led to higher percentages of mercury desorption compared to HCl, due to the higher affinity of desorbed Hg ions to re-adsorption onto the chloride containing groups have been introduced onto the adsorbents' surfaces after long time eluting with HCl. The performance of the sulfurized AC in cyclic mercury adsorption/desorption processes was not found satisfactory in comparison with the primary AC.