Hi everyone.
I am working on the adsorption of Congo Red over carbon material from residual biomasa, finding that the shape of the curve is in the oposite direction expected for this kind process. I Wonder if you can help me to understand the process, or if you know any reference regarding this non regular behavior or you have an explanation. I leave here the picture of the isotherm. Thanks a lot.
consider that you have two stages of adsorption. the first part of the curve is normal and then starts another stage. it might be related to change in adsorption mechanism or adsorption sites.
The isotherm of dry materials moisturizing has this shape. Were the conditions for process conducting the same, ie the time of reaching the state of equilibrium and the intensity of mixing? Has enough adsorbent been used? At low concentrations, the whole mass of the adsorbate could be adsorbed. Regards,
To start off I would like to point out that your isotherm is of Type II and not of Type III as you state. With your isotherm you can calculate a surface area with the BET equation. Also I think that you need to run a standard nitrogen adsorption experiment on your biomass derived carbon just to see what sought of adsorption capacity it has. Just because it is carbon does not mean that it has been activated or that it contains micropores. Finally, I do not know what the size of Congo Red is, so bear in mind that if it is a large molecule then only the External Surface Area, that is the area not including the micropores, would be available for adsorption.
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