Removal of phenylalanine from aqueous solutions with thermo-chemically modified corn cobs as adsorbents

Corn cobs were evaluated as raw material in the production of an adsorbent for phenylalanine removal from aqueous solutions. Batch adsorption studies were conducted at 25, 35 and 45 degrees C, respectively. Adsorption equilibrium was attained after 3 h and Langmuir, Freundlich, Temkin, and Langmuir-Freundlich models were tested for equilibrium description, with Langmuir-Freundlich providing the best fits. Adsorption kinetics was better described by a pseudo-second-order model. The predominant adsorption mechanism was verified to be of the pi-pi type of interaction between the aromatic ring of phenylalanine molecule and the graphene rings at the carbon surface. Other mechanisms were also observed. The maximum value of uptake capacity, 109 mg g(-1), was similar or higher than values encountered in the literature for other types of adsorbents. (C) 2012 Elsevier Ltd. All rights reserved.