ADSORPTION OF SOME SUBSTITUTED PHENOLS ON ACTIVATED CARBONS FROM A BITUMINOUS COAL

Adsorption at 298 K of phenol, p-cresol, m-chlorophenol, m-aminophenol, and p-nitrophenol from aqueous solutions on activated carbons obtained from an original and a demineralized bituminous coal has been studied. The adsorption capacity of the activated carbons depended on the surface area and porosity of the carbon, the solubility of the phenolic compound, and the hydrophobicity of the substituent. The relative affinity of the phenolic compound toward the surface of the carbon was related to the electron donor-acceptor complexes formed between the basic sites on the surface of the carbon and the aromatic ring of the phenol. The adsorption capacity of the carbon depended on the solution pH. As a result, the adsorption capacity began to decrease at a pH value that depended on the difference between the external and internal surface charge density, as measured by electrophoresis and pH measurement of the slurry, respectively.