Enhanced mercury adsorption capacity by sulfurization of activated carbon with SO_2 in a bubbling fluidized bed reactor

摘要

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 ℃ 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 HNO_3 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.