Zeolite has been used in this process as an adsorbent for removal of Cd2+ and Pb2+ from aqueous solution. I have Langmuir model agreement data.
Dear Shameran,
First, I would like to make some clarifications about the assumptions. Assuming that you are asking about surface adsorption isotherms for structurally (and energetically) homogeneous, highly microporous zeolite, the answer is yes, it is quite natural to apply the D-R fit while the Langmuir would be more scientifically appropriate for a monolayer adsorption on a flat surface.
You may check any of the derivations of the Langmuir equations freely available on the web as well as the following derivations at the following link to see why.
http://www.genchem.net/book/parta.pdf
Also, the usage of the D-R isotherm in studies similar to your applications is well documented too, e.g.
http://www.sid.ir/en/VEWSSID/J_pdf/84320080212.pdf
Best,
Slava
Dear Shameran,
Dubinin–Raduskevich isotherm model can be used to describe the sorption on both homogeneous and heterogeneous surfaces, therefore you can use it in your sorption. If you need any papers to help you, don't hesitate to ask, I will send it to you if you need.
Best regards
Sayed Metwally
Dear Dear Shameran,
This paper will help you in using D-R isotherm model.
The uptake of metallic cations on zeolites is an ion exchange process which is rate controlled by a diffusion limited mechanism.It is not correct to use models designed to follow surface sorption models. This is made plain in Ion Exchange, Helfferich,Mc Graw-Hill, published in 1962!
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