Equilibrium constant and mass transfer parameters are needed for the study of amoxicillin separation in any process involving adsorption in fixed beds. In this work, the adsorption of amoxicillin and 6-aminopenillanic acid in aqueous solution on activated carbon were studied using static adsorption tests. The adsorption capacity was found to be strongly dependent on the pH of the aqueous phase. The adsorption constants, overall mass transfer coefficients, and axial dispersion coefficients for amoxicillin and 6-aminopenillanic acid were determined, by moment analysis, from a series of step tests in a fixed bed packed with activated carbon. The total bed voidage and axial dispersion coefficient were estimated from blue dextran pulse test data at different flow rates. The results show that adsorption intensity increased with increasing temperature. Furthermore, the increasing trend of HETP with velocity suggests that axial dispersion and mass transfer resistance control the column efficiency. IntroductionAmoxicillin, with molecular dimensions of 15.622 Å × 18.785 Å × 6.645 Å [1], is one of the major b-lactam antibiotics due to its high spectrum of activity, high solubility, high rate of absorption, and its stability under acid conditions. In the industry, the majority of semisynthetic b-lactam antibiotics are prepared by chemical methods. These reactions typically involve costly steps such as subzero degree Celsius conditions (-30°C), and toxic organic solvents like methylene chloride and silylation reagents [2]. Therefore, the enzymatic synthesis of semisynthetic antibiotics is an interesting industrial process, since it reduces the number of reaction steps and decreases the amount and toxicity of waste products per kilogram of antibiotic [3]. However, in the enzymatic production of amoxicillin at 25°C and pH 6.5, when the maximum yield of antibiotic production is achieved, the reaction media is composed of the desired product (the antibiotic), undesired products (resultant from hydrolysis), and unreacted substrates. The recovery of these biomolecules from bioreactors may involve several methods of extraction and purification, playing an important role in the global economic productive analysis of the process [4]. Adsorption is often used in downstream processing using various interactions, e.g., ionic, hydrophobic, affinity, etc., for the recovery of biomolecules, namely antibiotics [5]. Activated carbon and synthetic adsorbents have been used to remove biomolecules in the liquid phase [6][7][8], but no information is available on amoxicillin. Therefore, the purpose of this work is to study the separation of amoxicillin from reaction media as well as to evaluate the parameters of antibiotic adsorption onto activated carbon. Experimental Chemicals and ReagentsAmoxicillin was kindly donated by Royton Ltda, Brazil. 6-aminopenicillanic acid (6-APA) and blue dextran were supplied by Winlab and Sigma-Aldrich, respectively. All other reagents were of analytical grade from different commercial brands. AdsorbentActivated ...