Effect of Different Treatment on the Adsorption of p-Cresol by Activated Carbon (Langmuir Isotherm)

Abstract

Adsorption of p-cresol by four activated carbons (one untreated and three treated) was carried out at 301 K and at controlled pH conditions. In acidic conditions such that pH of solution is well below the pK_a of p-cresol (molecular form), it was observed that the adsorbate solubility and the electron density of aromatic ring
and also those of the carbon surface, are the main forces involved
in the adsorption process, by affecting the extent of London dispersion
forces. In higher solution pH conditions (in ionic form), on the
other hand, it was found that the electrostatic forces played a significant
role on the extent of adsorption. The effect of pH must be
considered from its combined effects on the carbon surface and on
the solute molecules. It was found that the uptake of the molecular
form of the aromatic solute was dependent on the substituents of
the aromatic ring. Adsorption of the solute in higher pH values was
found to be dependent on the concentration of anionic form of the
solute. All isotherms were fitted into Langmuir isotherm equations
to find the relative factors.