Abstract
Adsorption amounts, obtained from the differences between initial and equilibrium concentrations roitin-6--sulfate and sodium carboxylatomethylcellulose by silica Micon FN from an aq, u oef- scohdoinudm ous solution of 0.9% NaCl exhibited negative values in the presence of poly (N -vinylpyrrolidone). Sur- face pore and interparticle void space due to the aggregation of Micon FN were responsible for the nega-ti ve adsorption. Water molecule could penetrate into them while polymer molecule could not owing t o it s large size, resulting in concentrating the polymer in the bulk phase during the adsorption. Three methods to estimate the void volume were theoretically and experimentally developed: (1) 2-steps dilution method, by determining the polymer concentration in the supernatants before and after diluti on with a known amount of the solvent;. (2) graphic method, through determining the negative slope of an isotherm of apparent/negative adsorption; and (3)Na+-activity method, by measuring the Na+-activity i n the presence of known amounts of a polymer and Micon FN. The void volumes (Vp), estimated through these 3 methods, coincided each other ( Vp = 2 - 6 ml/g of Micon FN). The true amounts of adsorption became positive after the correction by using Vp.
