Aqueous mercury and lead removal with activated carbons derived from high sulfur carbonaceous materials

Hg and Pb are of environmental concerns due to their toxic and bioaccumulative nature. Developing cost effective adsorbents for controlling their emissions to the environment is of practical value. In this work, the adsorption of aqueous Hg 2+ (200 - 400 ppm) and Pb 2+ (570 ppm) onto a series of activated carbons was investigated. The activated carbons used were prepared from high sulfur coal or petroleum coke via chemical activation processes using alkaline materials such as KOH and its mixture with other reagents. Activated carbons were analyzed for specific surface area, porous size distribution, total sulfur, as well as sulfur functional groups. The adsorption capacity was determined at controlled pH (5.0-6.0) and temperature (20-60°C) using ICP and AAS. The activated carbons had total sulfur contents from 0.16 to 20.14 wt%, and their specific surface areas varied from 47 to 2232 m2/g. A pseudo first order model was applied to describe the adsorption kinetics. Experimental data indicated that the increase in sulfur content and specific surface area enlarged the adsorption rate and capacity for both Hg(II) and Pb(II). The type of sulfur in activated carbons was found to be the most important factor in determining the effectiveness of adsorbing Hg(II) and Pb(II).