ADSORPTION OF 6-AMINOPENICILLANIC ACID ON ACTIVATED CARBON

The adsorption and desorption of 6-aminopenicillanic acid (6-APA) in a queous solution has been studied using activated carbon as the adsorbe nt. The extent of adsorption was found to tie strongly dependent on th e aqueous phase pH and this dependence could be interpreted from a mod el for neutral species adsorption. Desorptionstudies suggest that a sm all fraction of 6-APA adsorbs irreversibly on activated carbon. Adsorp tion equilibrium data were correlated with the Langmuir, Freundlich an d Redlich-Peterson expressions with the Langmuir model being found to provide the best fit of the experimental data. The rates of adsorption and desorption appear to follow the first-order kinetics under the ex perimental conditions used in the study. However, more precise rate ex pressions requires the inclusion of the external mass transfer effect initially and the particle diffusion effect at the later stage. Adsorp tion enthalpy calculated from the Van't Hoff plot was found to be 3.92 kcal mol(-1). (C) 1997 Elsevier Science B.V.