We are studying the adsorption of CO2 onto the activated carbon by which the adsorption mechanism is physisorption.

By comparing the models to the experimental data of the breakthrough curves (C/C0 with time), we see that the Thomas model and the pseudo second order fit but the pseudo first order model doesn't. And as we know the pseudo-first order describes the physisorption process but the pseudo-second order describes the chemisorption process. In our case, the process is physisorption, thus, I would like to ask you about the physical phenomenon behind that concerning the fitting of the models.