Swelling kinetics of polyvinyl alcohol gel in solutions of organic acids and their salts

Abstract

This study is devoted to the investigation and analysis of the kinetics of swelling of polyvinyl alcohol gel, initially in equilibrium with distilled water, in solutions of organic acids and their salts. The study presents the experimental data obtained by the optical micrometry method on the kinetics of swelling of PVA granules in solutions of aliphatic carboxylic acids and their sodium salts, depending on the concentration of solutions. A physico-mathematical model of swelling of a spherical granule of a polymer gel developed to describe the observed phenomenon is presented.

The study considers and generalizes the general properties of kinetic curves, obtained at registration of changes in the volume of PVA granules in ethane, propanoic, butanoic, and butanedioic acids, as well as in solutions of their sodium salts; formulate general conclusions about the patterns of change in the degree of swelling of PVA granules in these solutions, such as: total change in the volume of the gel, the presence and depth of the extremum, the effect of the length of the hydrocarbon radical and the number of carboxyl groups in the composition of acid molecules.

The algorithm for obtaining kinetic surfaces intended for the analysis of the concentrations of solutions of these compounds was developed based on the results of the study. In order to reduce the analysis time, the possibility of determining the concentration of dissolved substances based on the initial sections of the kinetic curves obtained in the analysed solutions using the optical micrometry method, was demonstrated.

Since, in order to obtain reliable data on the initial portion of the kinetic curve, it is necessary to quickly fix the granule in the cell, the kinetic results of measuring the volume of a PVA granule with added magnetite, which was fixed by a magnetic field are shown.