CONTRASTING ADSORPTION EXHIBITED BY LIGNITE-BASED ACTIVATED CARBONS

The adsorption of sodium benzoate, 2,4-dichlorophenol and 2,4,6-trichlorophenol onto five activated carbons made from Northern Ireland lignite is reported. A two-stage process consisting of chemical activation during the charring of the lignite, followed by steam activation was used to produce the activated carbons. The adsorption equilibrium isotherms obtained for the carbons have been plotted to obtain the Freundlich, Langmuir and Redlich-Peterson constants. Chemical and steam activation methods both produced improvements to the carbon performance on their own, with the combination of the two treatments providing the best results. In the main the chemical treatment providing the best improvement on its own also gave the biggest improvement when combined with steam treatment. BET surface area measurements made using nitrogen adsorption correlate strongly with the capacity for benzoate adsorption.