Adsorption of a Detergent Molecule

The detergent molecule, such as dodecyl ammoniumchloride, was found to adsorb 0.433 mM per gram of alumina with a surface area of 55 mVg. The surface area of alumina as determined from stearic acid adsorption (and nsing the aiea/molecule of 21 A from monolayer) gave the value of 55 mVg. 

The adsorption isotherms obtained for various detergents showed a characteristic feature that an equilibrium value was obtained when the concentration of detCTgent was over CMC. The adsorption was higher at dO C than at 20 C. However, the shapes of the adsorption curves were the same (Birdi, 2003a). Detergents adsorb on solids until CMC, after which no more adsorption is observed. This shows that after the solid surface is covered by a monolayer of detergent, the adsorption stops as the system reaches an equilibrinm. 

One can also calculate the amount of a small molecule, such as pyridine (mol. wt. 100), adsorbed as a monolayer on charcoal with 1000 mVg. In the following, these data are delineated  

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