A comparison of adsorption isotherms using different techniques for a range of raw, water- and acid-washed lignites

Adsorption isotherms based on desiccator measurements at 30 °C have been constructed for six Victorian lignites (five raw, one water-washed and six acid-washed samples). The results for a selection of samples have been shown to be in good agreement with more detailed isotherms obtained using two different automated microbalances. This suggests that the rate of approach to the final relative vapor pressure has little effect. The equilibrium moisture contents at 51.4% relative vapor pressure or less for the acid-washed lignite samples showed moderately good correlations (R2∼0.5) with the carboxylic acid concentration, but much weaker correlations with the phenolic content.