Langmuir Gas Adsorption

This equation assumes that only one layer of gas molecule adsorbs. A monolayer of gas adsorbs in the case in which there are only a given number of adsorption sites for a monolayer. This is the most simple adsorption model. The amount adsorbed, Ns, is related to the monolayer coverage, Nsm, as follows (Appendix C)  

From the experimental data, pFNs versus p can be plotted. The plot will be linear, and the slope is equal to 1/Nsm. The intersection gives a. Charcoal is found to adsorb 15 mg of N2 as monolayer. Another example is that of adsorption of N2 on mica surface (at 90 K). The following data were found  

The surface area of the solid can be estimated from the plot of piNs versus p. Most data fit this equation under normal conditions and are therefore widely applied to analyze the adsorption process. 

Langmuir adsorption is found for the data of nitrogen on mica (at 90 K). The data were found to be 

This shows that the amount of gas adsorbed increases by a factor 28/24 = 1.2 when the gas pressure increases twofold. 

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