Adsorption of Acetic Acid onto Activated Charcoal

1 Adsorption of Acetic Acid onto Activated Charcoal 

Adsorption at liquid surfaces can be monitored using the Gibbs adsorption isotherm since the surface energy, y, of a solution can be readily measured. However, for solid substrates, this is not the case, and the adsorption density has to be measured in some other manner. In the present case, the concentration of adsorbate in solution will be monitored. In place of the Gibbs equation, we can use a simple adsorption model based on the mass action approach. 

On any solid surface, there are a certain number of possible adsorption sites per gram (Nm), where any adsorbate can freely adsorb. There will be a fraction 0 of sites which are filled by one adsorbing solute. There will also exist an adsorption-desorption process at the surface. The rate of adsorption will be given as 

It is known that at equilibrium these rates must be equal  

Adsorption experiments are carried out as follows. The solid sample (for example, activated charcoal) is shaken in contact with a solution with a known concentration of acetic acid. After equilibrium is reached (after 24 h), the amount of acetic acid adsorbed is determined. 

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