Effect of structural and electrolytic properties of carboxyl-containing cellulose cationites on the sorption of cephalexin from aqueous solutions

Sorption of antibiotic cephalexin from aqueous solutions by monocarboxyl cellulose (MCC) samples with various content of carboxyl groups and structure (the degree of crystallinity) is studied. It is disclosed that the sorption occurs mainly due to electrostatic interactions via the proton transfer from carboxyl group of MCC to the carboxylate ion of cephalexin. The sorption is characterized by Langmuir isotherms and described by the equation of localized stoichiometric sorption. Sorption of cephalexin increases with the content of carboxyl groups in the sorbent phase, which is explained by the peculiarities of the dissociation of MCC carboxyl groups. Structural characteristics of MCC samples do not substantially influence the sorption of antibiotic. Dependence of the sorption value on the pH of equilibrium solution has a maximum at pH approximate to 3.5, which is explained by the specific features of the electrolytic dissociation of cephalexin and MCC.