Adsorption of cadmium by sulphur dioxide treated activated carbon

Merck carbon (1.5 mm) was treated in three ways: heating from ambient temperature to 900 degreesC in SO2; treatment at ambient temperature in SO2; or successive treatments in SO2 and H2S at ambient temperature. All samples were then characterised and tested as adsorbents of Cd2+ from aqueous solution. The characterisation was in terms of composition by effecting ultimate and proximate analyses and also of textural properties by N-2 adsorption at -196 degreesC. Kinetics and extent of the adsorption process of Cd2+ were studied at 25 and 45 degreesC at pH of the Cd2+ solution (i.e., 6.2) and at 25 degreesC also at pH 2.0. The various treatments of the starting carbon had no significant effect on the kinetics of the adsorption of Cd2+, but increased its adsorption capacity. The most effective treatment was heating to 900 degreesC, the adsorption in this case being 70.3% more than that of the starting carbon. The adsorption increased at 45 degreesC but decreased at pH 2.0 when compared to adsorption at 25 degreesC and pH 6.2, respectively. (C) 2003 Elsevier B.V. All rights reserved.