There are many other adsorption isotherms such as BET (multilayer adsorption), Fowler-Frumkin (includes lateral interaction but has a non-physical hysteresis in it), the t-plot (for porous matter) and more.

Can you describe your system or, if you are allowed to do that, share the shape of your graph?

In many articles, the maximum adsorption capacity has been reported experimentally, but its estimation way has not been explained. I like to know the experimental calculation way of the maximum adsorption capacity. Nevertheless, the obtained data in my study is attached.

Thanks so much for your answer.

The extent of adsorption in heterogeneous catalysis for surface coverage is normally expressed as a fractional coverage, (angle) as the number of adsorption sites occupied divided by the number of adsorption sites available. The fractional coverage is often expressed in terms of the volume of adsorbate

Alternatively, you can use the Dubinin-Radushkevich (D-R)model to find qm.However, it is a very complex and difficult model to calculate.