Equilibrium and Do−Do Model Fitting of Water Adsorption on Four Commercial Activated Carbons with Different Surface Chemistry and Pore Structure

Abstract

The textural properties and the surface acidities of four commercial activated carbons (ACs) were determined separately by nitrogen adsorption and Boehm titration. The adsorption isotherms of water vapor on the ACs were measured by the gravimetric method and fitted by the simplified version of the Do−Do (DD) model. The results indicated that all isotherms of water vapor on the ACs can be well-fitted by the simplified version of the DD model. The value of parameter n in the model increases with the pore size of the AC and is very close to 5 when the average pore diameter is between (1.96 and 2.8) nm. The order of parameter N0 is in good agreement with that of the total surface group concentrations. The parameter CμS is almost equal to the amount adsorbed of water on the AC at a relative humidity of 100 % or to the value of its total pore volume. The parameter Kμ depends on the pore size and decreases with increasing pore size. The value of parameter b depends on the combined contribution of the pore size and total surface group concentration of the AC and increases with the total surface group concentration and pore size.