THE ADSORPTION OF CERTAIN SEMISYNTHETIC CEPHALOSPORINS ON ACTIVATED CARBON

The adsorption of semi-synthetic cephalosporins such as 7-aminocephalo sporanic acid (7-ACA), cephalexin and cefadroxyl from aqueous solution has been studied using activated carbon as the adsorbent. The pH depe ndence of the adsorption intensity could be interpreted from a model f or neutral-species adsorption. 7-ACA exhibited relatively low adsorpti on intensity compared to cephalexin and cefadroxyl, whose adsorption i ntensities were nearly equal. The adsorption isotherm for all the thre e could be interpreted from the Langmuir model with a reasonable degre e of accuracy. The adsorption-rate curves for the cephalosporins exhib ited identical patterns at pH 7-8. The concentration-time profiles gen erated for cephalexin in an agitated slurry system indicate that exter nal film diffusion controls the solute uptake initially, and particle diffusion controls solute uptake in the later stages. (C) 1997 Elsevie r Science B.V.