Modeling of multi-temperature IV and V-type water vapor adsorption isotherms on activated carbons for chemical protection

Abstract

A static volumetric method measured the water vapor adsorption isotherms on porous activated carbons (AC and ASC-T) at 278.15 K ～ 308.15 K. Because of the difference in surface oxygen-containing functional groups, a Type-V isotherm represented water vapor adsorption on AC, whereas a Type-IV isotherm characterized ASC-T. The applicability of seven classical adsorption equilibrium models was analyzed and compared systemically. Results show that the Dual-sites Langmuir-Freundlich equation had the lowest residual errors (< 6 ml/g). Further, based on the linearization DA equation, a new partitioned segment-fitting strategy was first developed to describe multi-temperature adsorption isotherms. Two sets of the division points (P/P0) and parameters (n) were acquired. For AC and ASC-T, the best division point (P/P0) and parameter (n) were equal to 0.1 and 0.9, 0.2 and 2, respectively. The fitted results of multi-temperature adsorption isotherms show that the R2 values of AC and ASC-T both were bigger than 0.93, showing that the new fitting strategy has very good applicability. It offers the possibility to address the problem of the accurate description for multi-temperature water vapor adsorption data on porous activated carbons.