How to distinguish between physical adsorption and chemical adsorption, when we know deltaH, deltaS and delta G values?
http://www.fisica.unige.it/~rocca/Didattica/Surface%20Science%20and%20Nanostructuring/6%20adsorption%20at%20surfaces.pdf
http://www.majordifferences.com/2013/02/difference-between-physical-adsorption.html#.WGT7cFz-G5Q
http://www.chem.qmul.ac.uk/surfaces/scc/scat2_4.htm
http://faculty.ndhu.edu.tw/~yslo/_private/surface%20chemistry/Lecture-5.pdf
Some links which may be useful
When delta H is less than 40 kJ/mol, adsorption is considered to be physisorption.
It seems that the delta H value corresponding for physisorption is less than 35 kJ/mol in one of the materials provided by Dr. Banhegyi. There is some variation in this value depending on the source. However, 40 kJ/mol is the value frequently used in some recent adsorption publications.
We should know the values of energy of activation for defining physical/chemical adsorption. This is better method!
Chemical adsorption has delta H more than 40 kJ per mole whereas physical adsorption has deltaH less than 40 kJ per mole. Physical adsorption is a multilayer adsorption in which the first layer is adsorbed on the adsorbent and the other layers condense on the first layer. Chemical adsorption (chemisorption) is a single layer adsorption.Chemical adsorption has lower delta S value than physical adsorption
Renu Bisht
I suggest read my publication "
SORPTION KINETICS, THERMODYNAMICS AND REGENERATION
FOR LIPID FEEDSTOCK DEACIDIFICATION USING A MIXED-BED
ION-EXCHANGE RESIN"
If after reading even you do not understand please email me but first you give it a try.
Simple difference:
Chemical adsorption is characterized by lowerer delta S and higher delta H values
The point of view of thermodynamic > delta G is less negative on physical adsortion that on chemical adsortion., delta H must incresed negatively on chemical adsortion.
Differences between Physisorption and Chemisorption
1. The negativity of ∆H° increases rapidly in chemical adsorption, than in physical adsorption.
2. Also, the values of ∆H° range from 1-40 kJ/mol in physisorption, while ∆H° in chemisorption is higher than 40kJ/mol.
3. The values of ∆H° is much larger in chemisorption compared to the values of ∆S°. In physisorption, the values of ∆H° is lower compared to ∆S that is larger.
Read my Journal in Elsevier with this link
https://doi.org/10.1016/j.cherd.2019.10.016
Differences between Physisorption and Chemisorption
1. The negativity of ∆G° increases rapidly in chemical adsorption, than in physical adsorption.
2. Also, the values of ∆H° range from 1-40 kJ/mol in physisorption, while ∆H° in chemisorption is higher than 40kJ/mol.
3. The values of ∆H° is larger in chemisorption compared to the values of ∆S°. In physisorption, the values of ∆H° is lower compared to ∆S° that is larger.
Read my Journal in Elsevier with this link
https://doi.org/10.1016/j.cherd.2019.10.016
Good differentiation between physical and chemical adsorption on the basis of thermodynamical properties
Dear Yusuf,
the ratio of qe/ce is an non-valid way to calculate thermodynamik properties. This ratios is not equivalent to an equiblibrium constant obtained by the law of mass action.
The use of the langmuir constant give an appropiate result.
Liu, Y. Is the Free Energy Change of Adsorption Correctly Calculated? J. Chem. Eng. Data 2009, 54 (7), 1981–1985.
And i would recomment to read this papers too:
(1) Zhang, J.-Z. Avoiding Spurious Correlation in Analysis of Chemical Kinetic Data. Chem. Commun. 2011, 47 (24), 6861.
(2) Canzano, S.; Iovino, P.; Leone, V.; Salvestrini, S.; Capasso, S. Use and Misuse of Sorption Kinetic Data: a Common Mistake That Should Be Avoided. Adsorption Science & Technology 2012, 30 (3), 217–225.
(3) Tran, H. N.; You, S.-J.; Hosseini-Bandegharaei, A.; Chao, H.-P. Mistakes and Inconsistencies Regarding Adsorption of Contaminants From Aqueous Solutions: a Critical Review. Water Res. 2017, 120, 88–116.
Please read my publication "Sorption kinetics, thermodynamics and regeneration for lipid feedstock Deacidification using a mixed‐bed ion‐exchange resin" Article Sorption Kinetics, Thermodynamics and Regeneration for Lipid...
all the details you want
THANKS
Hello Yusuf,
I read your publication. And your publication contains a failure as I wrote. Read the publications I attachted.
It was reported that the change of free energy for physical sorption is in the range of −20 to 0 kJ/mol, while chemical sorption is between −400 and −80 kJ/mol [34]. Support Thomas Mayer-Gall .Thomas Mayer-Gall
The decission on physisorption or chemiesorption i would not fix alone one my thermodynamik parameters. the main faktor for a descission is, do I understand the chemistry behind my adsorption process? What do I know about the surface of my adsorbent?