Adsorption of phenol by bentonite

The potential of bentonite for phenol adsorption from aqueous solutions was studied. Batch kinetics and isotherm studies were carried our to evaluate the effect of contact time, initial concentration, pH, presence of solvent, and the desorption characteristics of bentonite. The adsorption of phenol increases with increasing initial phenol concentration and decreases with i ncreasing the solution pH value. The adsorption process was significantly i nfluenced by the solvent type in which phenol was dissolved. The affinity o f phenol to bentonite in the presence of cyclohexane was greater than that in water and was lowest in the presence of methanol. Methanol was used to e xtract phenol from bentonite. The degree of extraction was dependent on the amount of phenol adsorbed by bentonite. X-ray diffraction analysis showed that the crystalline structure of bentonite was destroyed when cyclohexane was used. The ability of bentonite to adsorb phenol from cyclohexane decrea sed as the water to cyclohexane ratio was increased. Furthermore, hysteresi s was observed in phenol desorption from bentonite in aqueous solutions. Th e equilibrium data in aqueous solutions was well represented by the Langmui r and Freundlich isotherm models. The removal of phenol from aqueous soluti ons was observed without surface modification. (C) 2000 Elsevier Science Lt d. All rights reserved.