Sorption of Methylene Blue by Polysorb MP from 40 and 95% Aqueous Solutions of Alcohol

Abstract

AES ICP, CHNS, TGA, and capillary electrophoresis are used to determine the chemical composition of medical enterosorbent Polysorb MP (colloidal particles of silicon dioxide) and the dispersion medium in contact with it. Polysorb dispersions in water, 40 and 95% water–ethanol solutions are obtained and characterized via photon-correlation spectroscopy (PCS) and the phase analysis of scattered light (PALS). The average hydrodynamic diameter of fractal-like aggregates of primary particles is 105–135 nm, and the electrokinetic potential varies from −28 to −22 mV. The charge of one aggregate falls as the content of alcohol rises in the order −89, −54, and −29 e. The maximum sorption of methylene blue falls sharply, from 10 to 0.7 mg/g. It is shown that the values of limit sorption considerably higher than the number of negative surface centers calculated according to PALS in the spherical aggregate model, but are less than the number of silanol groups found by TGA. A hypothesis is made about the mechanism of cation exchange during Polysorb MP’s sorption of cationic dyes.