Adsorption of zwitterionic drugs on oxidized cellulose from aqueous solutions

Adsorption of zwitterionic drugs (beta-lactam antibiotics and amino acids) on samples of oxidized cellulose (OC) with various carboxyl contents and structure characteristics from aqueous solutions was investigated. It was established, that drug binding with OC occurs via proton transfer from carboxyl group of ion exchanger to the carboxylate ion of adsorbed zwitterion. The adsorption process can be described according to the theory of localized stoichiometric adsorption and represented by Langmuir-like isotherms. The constants of sorbate interfacial distribution with some exceptions increase with a growth of sorbate relative hydrophobicity. The drug uptake is shown to increase with an increase of carboxyl content in the OC phase. The degree of crystallinity of sorbent has no considerable effect on drug adsorption from aqueous solutions. (C) 2005 Elsevier B.V. All rights reserved.