Dear Rumi Narzari , indeed the kinetic and isotherm model dont provide the information about mechanism . For mechanism evaluation you must go a head to use different spectroscopic techniques rather than evaluating it on the basis of models.

I agree the response of colleague Rumi Narzari and good luck.

Rumi Narzari Langmuir adsorption implies surface single layer sorption while BET implies multilayer adsorption the kind you would find on activated carbon where the adsorbate can infiltrate deep into the pore structure of the adsorbent. multilayer adsorption is probably better as a larger surface area per g of adsorbent can take part in adsorption meaning more adsorbing power over cost (to generalize).

Dear Rumi Narzari,

Sorption mechanism can be tricky however, both adsorbent and adsorbate characterization are important. This is done to determine if the is attachment of adsorbate on the surface of the adsorbent. This is done by techniques such as Raman, FTIR, XPS, SEM, TEM, and so on. Then the equilibrium studies such as adsorption isotherms, kinetic,s, and thermodynamics provide information on how the interaction between the adsorbent and adsorbate has proceeded.

The compatibility of Lagmuir's isotherm with the equilibrium data can be explained theoretically and related to monolayer sorption. However, if we add this to the agreement of the empirical hyperbolic function, i.e. the so-called PSO with an individual kinetic curve, such results as a whole will be scientifically worthless. Of course, such results can be used in practice.

Mirosław Grzesik Some top researchers accept these results and relations between the models when something not click in your mind it does meant it is worthless.

All the answers and information's provided by all researchers are noteworthy but the deep understanding regarding the mechanism evaluation still needs many spectroscopic characterization as it will provide you more valuable information's.

Thanks Dear Professor Dr Nibou Djamel

Zeeshan Ajmal, You are absolutely right. that only in-depth physicochemical studies can give information about the adsorption mechanism.

Thanks Dear Professor Mirosław Grzesik

Asif Ayub, I should ignore your post, but it's a science portal and arguments count. You wrote: "Some top researchers accept these results and relations between the models". Therefore, can you prove the relationship between the hyperbolic function with respect to Ce (Langmuir isotherm) and the hyperbolic function with respect to time (the so called PSO)? I am eager to read such evidence.

Well, many top researchers accepting results doesn't mean the theory is a law. If we take back the history of chemistry, for a long time Aristoteles' theory on four elements was accepted as the truth, instead of atom theory by Democritus. I think it's naive to accept Langmuir as a law, describing the entire mechanism of adsorption, considering the state of art of adsorption by that time. In that sense, I completely agree with Mirosław Grzesik , you can have a north using langmuir, but don't expect to understand completely your system just with it.

Luiz Fernando de Sousa Lima, Langmuir's equation can be derived from the fundamental law of mass action, and from this point of view I would treat it as a law. Of course, based on the Langmuir isotherm, we are not able to reliably explain all phenomena on the adsorbent surface. Some, however, we can explain, such as monolayer adsorption.

Mirosław Grzesik You're completely right. However, I still see it as a law under its boundaries conditions, (for example homogeneity, adsorption closer to chemical instead of physical..), and for cases which it fits experimental data (if your isotherm doesn't fit the model, than it's not described by its law). That said, I'd be more precise if I said that It's not a general law, that can solve all the problems on adsorption. If the later was the case, we wouldn't see freundlich, BET and many others models for adsorption.

Luiz Fernando de Sousa Lima, I agree that each physical equation has a limited range of applicability, because it was derived under certain assumptions. The wider has BET or GAB and the narrower Langmuir. But I wonder why you equate the boundary conditions with certain features of the adsorbent surface or the mechanisms of adsorption?

To justify how using Langmuir equation is not enough to describe the entire process of adsorption, as suggested by someone else earlier in this discussion, and the fact that "top researches" accepting this like a dogma shouldn't be enough for scientist to assume this as the ultimate truth on adsorption haha

Luiz Fernando de Sousa Lima, Ultimate truth has no place in science. Unfortunately, there are some "ultimate truths" in adsorption. The top one is the so-called PSO and the connection of this empirical hyperbolic function with the mechanism of chemisorption. This is utter nonsense by Ho and McKay, unfortunately duplicated in hundreds of works. This, however, cannot be summed up "ha ha"

Mirosław Grzesik This later is not a laughing by any joke, is usually something that people write at the end of some conversations to imply that they are being friendly on any kind of discussion.

Luiz Fernando de Sousa Lima, OK. I took it literally. In Polish "ha ha" can be associated with laughter and in this context I used it. Thanks for the clarification.