RL = 1/(1+ KL*Ci)
it is calculated using this formula, which Ci to taken exactly?? also I have seen many researchers mention it as equilibrium concentration. so is it equilibrium concentration or initial concentration.? We have multiple sets of readings which Ci should be taken.
Please help.
Kindly provide references too.
I appreciate any help you can provide.
Dear Ayushi, Ci represents the equilibrium concentration. Whoever says it is the initial concentration is wrong!
For instant, this paper,
https://www.jmaterenvironsci.com/Document/vol4/vol4_N3/60-JMES-361-2013-Meroufel.pdf
where it is said that Ci is the initial concentration and even named as C0
(formula (5), pave 487); you'll find references (35-37) in the final section.
Hope this could help!
Otherwise, this paper might be very interesting (if you work closely on Langmuir model):
Article Quantification of the limitation of Langmuir model used in a...
Just because something is published, it does not mean it is correct. There is a lot of nonsense out there.
This paper refers a "linear langmuir adsorption isotherm" - which does not exist. You can compute a linearized form of an adsorption isotherm - which is also unnecessary, as you can compute the parameter by non-linear regression.
If you want to calculate the separation factor, you can use IAST where you can define the selectivity as S=(Yi/Xi)/(Yj(Xj) for each cTotal or you go with the linear region of the isotherm. The linear region is called "Henry regime". If you want to define a separation factor in the Henry regime, you just need to calculate the quotient of the Henry constants. There RL definition is useless.
If you use C0 for a caluclation, you also must use the amount of adsorbent. Otherwise the results would not be comparable.
Adsorption isotherms are per definition an equilibrium isotherms.
If you have fundamental questions about adsorption I recommend a text book (preferably by a serious publisher), not a paper from a non scopus/webofscicnece indexed journal.
Dear Ayushi Mishra ,
As indicated by Thomas Waluga it is important to check the proper and trusted papers. For example, one of the references [36] in the paper suggested by Gabriela Dima is referred to as:
Zacar M.O., Engil I.A.S. Adsorption 8 (2002) 301.
While the real reference is:
Özacar, M., & Şengil, İ. A. (2002). Adsorption of acid dyes from aqueous solutions by calcined alunite and granular activated carbon. Adsorption, 8, 301-308. (I will send you the paper, here you can read that we are not dealing with the Langmuir isotherm perse but more with a derivative that transforms things into linear correlations allowing to’ simply’ use slope and intercept).
In other words, the reference is not accurately given which makes you wonder about the quality of the peer review.
Disclaimer: Not entirely my field of expertise but since you have all sorts of absorption I am not sure how general applicable a formula as you want to use will be.
I think the following paper is the origin of the formula you’re trying to use: Hall, K. R., Eagleton, L. C., Acrivos, A., & Vermeulen, T. (1966). Pore-and solid-diffusion kinetics in fixed-bed adsorption under constant-pattern conditions. Industrial & engineering chemistry fundamentals, 5(2), 212-223. (I will send you the paper, you will see formula (3) and in the text they talk about feed concentration co which I guess nowadays would be called initial concentration).
For an excellent overview see for example:
Swenson, H., & Stadie, N. P. (2019). Langmuir’s theory of adsorption: A centennial review. Langmuir, 35(16), 5409-5426. (Just go to Google Scholar for a downloadable version)
Best regards.
PS. In the following question here on RG you find some helpful replies: https://www.researchgate.net/post/How_can_separation_factor_RL_calculated_through_Langmuir_isotherm_model_serve_as_an_invaluable_factor_in_the_adsorption_process
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