Question
Asked 2 September 2024

How can I predict mechanism of adsorption either chemisorption or physisorption from Langmuir isotherm?

I have performed the adsorption studies and applied Langmuir model to the data. I obtained KL value from it. In literature it is given higher the KL value stronger the interaction between adsorbent and adsorbate. But there isn't any specific value of KL given.
In literature FTIR and XRD are also performed to predict the adsorption mechanism. I have done that as well and there is shift and change in the peak intensities.
Which one is better to predict the adsorption mechanism? Either from KL value or FTIR/XRD?

Most recent answer

Basem E. Keshta
Tanta University
From the D-R model, u can consider physical adsorption or chemisorption; when E<8 kj/mol is physisorption, 8 kj/mol<E<16 kj/mol is chemisorption. and also you can find these references will help you
1-Influence of Synthesis and Functionalization Procedures of Fe3O4 NPs by Mono- and Diamino Silane Coupling Agents on the Adsorption Efficiency of Anionic Dyes
2-Cutting-edge in the green synthesis of MIL-101 (Cr) MOF based on organic and inorganic waste recycling with extraordinary removal for anionic dye
1 Recommendation

All Answers (6)

Yuri Mirgorod
South-West State University
If you have adsorption from a solution, then the Langmuir isotherm is derived using the thermodynamic method. The thermodynamic method does not provide adsorption specificity. The method says that adsorption into one monomolecular layer occurs due to physical adsorption or chemisorption.
KL characterizes the equilibrium constant of the reaction, that is, the equilibrium bias towards adsorption. You can determine the binding specificity by comparing the peaks of the IR spectra of the adsorbate in the solution and on the surface of the adsorbent.
1 Recommendation
Asma Siddiqa
University of Rajshahi
From D-R model u can consider physical adsorption or chemisorption, When E<8 kj/mol is physisorption, 8 kj/mol<E<16 kj/mol is chemisorptin.
1 Recommendation
Noor Ul Ain
COMSATS University Islamabad
Yuri Mirgorod Thank you for your guidance.
Can I say it from shift or appearance of new peaks in IR spectrum that possible interaction is either chemisorption? or from XRD?
Asma Siddiqa
University of Rajshahi
yes obviously, after chemisorption, IR spectra shifted to higher frequency data and XRD analysis gave less crystalline phase.
1 Recommendation
Yuri Mirgorod
South-West State University
I wrote, if there is a shift of peaks of some functional group, then you can discuss this chemisorption. That is the same for XRD, but I am not sure that crystallinity will change. Perhaps Asma Siddiqa right about less crystalline phase in nanoparticles after adsorption of molecules. .
1 Recommendation
Basem E. Keshta
Tanta University
From the D-R model, u can consider physical adsorption or chemisorption; when E<8 kj/mol is physisorption, 8 kj/mol<E<16 kj/mol is chemisorption. and also you can find these references will help you
1-Influence of Synthesis and Functionalization Procedures of Fe3O4 NPs by Mono- and Diamino Silane Coupling Agents on the Adsorption Efficiency of Anionic Dyes
2-Cutting-edge in the green synthesis of MIL-101 (Cr) MOF based on organic and inorganic waste recycling with extraordinary removal for anionic dye
1 Recommendation

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