Porosity by Physical Adsorption

Classically, micropores have been treated using the Langmuir [19, 20] isotherm with the assumption that since the micropores were too small for 

Another possibility in analyzing for micropores is to modify the BET equation to allow for only a certain number of monolayers to adsorb. This introduces another parameter, i.e. the number of allowed monolayers. This equation is not widely used and has not proven to be successful. With N being the number of allowed layers, the modified equation, called the BDDT [21], is 

Mesopores generate either a type IV or V isotherm. In types IV and V isotherms a similar strategy as that for micropores can be used as illustrated in Fig. 14. Notice, however in this case that the lower line, L, and the upper line, H, intersect at a higher value of x than the commencement of the negative change in the slope. The analysis from these lines remains the same as for the micropore case (Fig. 13), but there is additional information. One could refer to such pores as pre-filled or capillary filled since it is normally attributed to capillary action. Notice that this particular part of the analysis an answer for the pore volume, total surface area and external surface area is independent of whether the adsorption or desorption branch of the isotherm is used. 

The interpretation of the hysteresis loop is a matter of some current discussion. The primary explanation is based upon the Kelvin equation as modified by Cohan [22]. which is  

The following are the meanings of the new symbols, yis the surface tension of the liquid adsorptive, the liquid adsorptive molar volume, the pore 

---