Even though OH group present in the surface of carbon, but still it doesn’t absorb selected dye solution. What may be the reason for this? What may be the reason that activated carbon doesn’t absorb any dye solution?
Activated carbon is normally used as an adsorbent in water and wastewater treatment. Adsorption and absorption are different processes. Activated carbon can prepare from any carbonaceous materials. Researches on dye removal by activated carbon adsorption has been conducted by several researchers. You can download that papers. For further clarification please contact me at [email protected]
The activated carbon can adsorb heavy metals very well. But, dye solution can not be adsorbed on the activated carbon easily that activated carbon doesn't have functional groups suitable for dye molecules. The other reason may be becasue of the steric effect. Dye molecules are very big, so, the steric efffect can block the molecules.
Because of the high surface area, activated carbon is one of the important candidate in wastewater treatment. The activated carbon can adsorb some of dyes. It's depends on the chemical structure of dye.For example azo dyes can be adsorbed on activated carbon easily. There are so many research paper in this area.
GAC is an effective adsorbent for chemicals, including dyes, that are "hydrophobic" - i.e. has very low solubility in the water phase. Dyes or chemicals that can form "hydrogen bond" with water, such as alcohols, acids, esthers, ketones are "hydrophilic" and will not be good candidates for GAC adsorption.
As far as I am aware, the book "Activated Carbon Adsorption" authored by the late Prof. Henrich Sontheimer, Prof. John C. Crittenden, and Prof. Scott Summers and published by the American Water Works Association is the definitive reference when it comes to using GAC for Water Treatment purposes.
Absorption differs from adsorption. Colour reduction can easily be observed with substrates that have high fibre, however, substrates like activated carbon, with low fibre are good for adsorption studies. Many papers have been published in this area, make appropriate literature search to choose the right substrate for your dye material. You can use the functional groups on the dye and the substrate for a quick guide.
Absorption is a whole phenomena in which molecules may pass through the whole material. If the dye having molecular size same or smaller than of carbon surface pores, it will absorb. Larger the molecular size, absorption becomes difficult. Presence of phenolic goroups, at suitable pH some molecules may adsorb on the surface by means of Hydrogen bond formation or weak vander waal's force.
You may want to try clay adsorbents such as attapulgite for efficient dye removal.
Hole functional group try to form peroxide bond I think in your dye there is no free oxygen so dye is unable to interact with molecule
Adsorption of dyes by activated carbons has been well documented in the recent literature, which emphasized about the influence of point zero charge, surface chemistry and characteristic pore size. If neither the basic characteristics of your activated carbon (e.g. is it rather micro or mesoporous, what is the surface area and the main pore size, what is the pHzc, ?, etc.) nor the kind of dye (cationic, ...?) are known, then nobody can answer your question. For example, if the surface of your activated carbon is positively charged at the pH you want to adsorb a cationic dye, then it is obvious that almost no adsorption will occur. More details about your adsorbent/adsorbate system are required.
Alain
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