A new dynamic volumetric method (DVM) is described for measuring adsorption isotherms on small surface area solids such as glass fiber. The experimental setup of the method is the same as that of frontal analysis (FA) chromatography. However, whereas FA analysis is based on the local mass balance equation (mass balance in each cross section of the column), this DVM is based on the global mass balance between the inlet and outlet of the system. It differs from the static volumetric method in that the latter measures an adsorption isotherm in the state of adsorption equilibrium, whereas the DVM does the same in the steady state. This difference creates a problem of determining equilibrium adsorption concentration in the DVM which does not exist in the static method. It is shown how to resolve that problem. The DVM is more general than FA and is applied here for determination of the BET specific surface areas (SSA) of glass fibers using water. The results are compared with those obtained by standard SSA determinations with Kr and those obtained by measuring glass fiber diameter and density. In some cases, the SSAs obtained by the three different methods reasonably agree with each other. In other cases, however, the SSA obtained by water proved to be considerably larger than that obtained by the two other methods. Because water is reactive with glass fibers, this could be an indication of nanoscale surface properties of glass fibers which cannot be detected by Kr adsorption. Surface area analysis is not typically performed in packed columns, so this development expands the applicability of chromatographic columns in general.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
- General Energy