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

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 appli-cability 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 lineari-zation 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 re-sults 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.

Automated summary

This study used a static volumetric method to measure the water vapor adsorption isotherms on porous activated carbons. Different oxygen-containing functional groups on the surface resulted in a Type-V isotherm for activated carbon and a Type-IV isotherm for ASC-T. The Dual-sites Langmuir-Freundlich equation showed the lowest residual errors, and a new partitioned segment-fitting strategy was developed to accurately describe multi-temperature adsorption isotherms.