Most of research shown for activated carbon adsorption fitted well with Langmuir isotherm which shown by bigger correlation compared to other.
First, the determination of Langmuir isotherm allows to know the maximum capacity of adsorption of adsorbents as activated carbon. Secondly, in industrial applications this important propriety must be known.
Basically, if we know what isotherm model fitted the most, we can estimate the characteristic or behavior of the adsorption process . Each model comes with their assumptions. For example, if Langmuir fitted model actually based on the assumption that only a monomolecular layer of noninteracting solutes is formed dynamically on the sorbent surface, with all adsorption sites being of equal adsorption energy.Same goes to other isotherm models. So, from that you can estimate your max capacity of adsorbent and other required information. And make sure the assumption made is logically to be consider according to your case study.
Norfahana Abd Talib thank you for the explanation. Is there any relation of isotherms fitted with a concentration of ions adsorbate. Since, some say that isotherms independent of ion concentration but it depends on what info that we're finding. But, I also find out that, Freundlich favors high concentration of adsorbate but vice versa for Langmuir. Correct me if I'm wrong. Thank you .
Adsorption isotherm describes the equilibrium performance of adsorbents when the temperature is constant. The different between Langmuir and Freundlich is langmuir assume the tickness layer of the adsorbed layer is mono, all sites have equal affinity towards the adsorbate . But for Freundlich assume not stricted to the monolayer adsorption. Its applicable to the multilayer.
yupp correct. isotherm model is something independent from the adsorbate concentration and as i know Freundlich isotherm has problems in relative higher concentrations, while the other isotherm models like Langmuir isotherm can overcome the Freundlich limitations. Practically there is no difference between adsorbate concentration and fitment of isotherm models. However, it may sometimes happen that, with the increase in adsorbate concentration ..
Only my 2 cents
Norfahana Abd Talib thank you again! I really appreciate the explanation given. I'm curious about why do most of the studies on adsorption (based on research papers) show Langmuir fitted the best? Does this conclude anything?
We cannot simply claim as Langmuir is dominant but if it’s really happened maybe because of Langmuir (so called as ideal adsorption behavior) hypothesize these criteria:
And majority of the whatever behavior is close to ideal or approaching to ideal behavior. And most of the researcher tend to simplify the works by neglecting the minor contribution factors.
After all, Langmuir adsorption model deviates significantly in many cases, primarily because it fails to account for the surface roughness of the adsorbent and this assumption may be justified for small molecules, it is unlikely to be realistic for large ones, and often more industrially important molecules.
Just my 2 cents
Thanks
Norfahana Abd Talib Thank you for the clarification on this matter :) I'm currently conducting my FYP on adsorption. Thanks for the help!
Norfahana Abd Talib Zeeshan Ajmal Nibou Djamel Hi! Can i seek your expert opinion and knowledge regarding this:
Physisorption depends on surface area of adsorbent only while chemisorption depends on surface area and surface charges / functional groups ?
Is my understanding true?
The description of each experiment requires an individual approach. Statistical data can only be a guideline.
Dear Nur ikhsan Bujang ,
On the basis of surface are, surface charge or functional group we can not predict the exact mechanism of target pollutant over adsorbent surface sites. Even models also don't provide the exact information about that. For that purpose we need to know the deep understanding about targeted pollutant fate, their transport, as-synthesized material characteristics including its all physico- chemical properties, different spectroscopic techniques. Moreover the Norfahana Abd Talib shared a good article for you please go a head and get a deep understanding. Thanks
Nur ikhsan Bujang, The type of interactions between the adsorbate molecules and the surface are important. The surface area does not matter here. I wonder what work this sentence comes from?