CONTRASTING ADSORPTION EXHIBITED BY LIGNITE-BASED ACTIVATED CARBONS

The adsorption of sodium benzoate, 2,4-dichlorophenol and 2,4,6-trichl orophenol onto five activated carbons made from Northern Ireland ligni te is reported. A two-stage process consisting of chemical activation during the charring of the lignite, followed by steam activation was u sed to produce the activated carbons. The adsorption equilibrium isoth erms obtained for the carbons have been plotted to obtain the Freundli ch, Langmuir and Redlich-Peterson constants. Chemical and steam activa tion methods both produced improvements to the carbon performance on t heir own, with the combination of the two treatments providing the bes t results. In the main the chemical treatment providing the best impro vement on its own also gave the biggest improvement when combined with steam treatment. BET surface area measurements made using nitrogen ad sorption correlate strongly with the capacity for benzoate adsorption.