Adsorption of Cd2+ by heat-treated and sulfurized activated carbon

Activated carbon (AC) and samples prepared by treatment of the material under different temperature conditions and atmospheres (H2S, SO2, N-2) were used in the adsorption of Cd2+ ions from aqueous solutions. The adsorption isotherms for Cd2+ were determined at 25, 35 and 45 degrees C at unchanged pH of the adsorptive solution, and at 25 degrees C also at pH 2.0. The treatments of AC, and especially when the material was heated in N-2, resulted in a significant increase in the adsorption of Cd2+. The pH change in the Cd2+ solution whether substantially decreased the adsorption of metallic ion or not depending on the adsorbent. The adsorption of Cd2+ decreased greatly at the higher temperatures. Kinetics of the adsorption process was faster when AC was heated in H2S, and slower when the material was treated successively in SO2 and H2S. Generally, the adsorption process decelerated at the lower pH value. However, it was accelerated with the temperature increase. For the sample prepared in SO2 and H2S, kinetics was almost isensitive to pH and temperature changes.