Commercial films of stereoregular isotactic polypropylene (PP) are the objects of the study. The aim of the work is to substantiate the mechanism of the previously observed weight loss of the PP films as a result of consequtive sorption of hydrophobic and hydrophilic substances, while considering PP as a combination of hydrophobic and hydrophilic localized and delocalized sorbents. A variable sequence of the processes of sorption of probe molecules with different polarities is used as an investigation method, while only an analytical balance serves as a research instrument. It is shown that the weight loss of PP films during the sorption of a hydrophilic substance (water) after their preliminary swelling in a hydrophobic sorbate (hexane) containing a small amount of native water is caused by complexation of water molecules with hydrophilic impurities. As a result, a reverse flow of these complexes out of the polymer occurs along the transport channels that arise during its swelling in the hydrophobic sorbate (hexane).

An unusual effect is observed that occurs during the sorption of liquids by polymers: The sorption flux directed from the liquid into the polymer bulk transfers only the sorbate, while the spontaneously established backward flux carries a sorbate‒impurity complex into the liquid. It is shown that this effect can be used to remove hydrophilic impurities from a hydrophobic polymer. It is assumed that delocalized (and mobile) sorbent particles participate in this phenomenon and include them in the proposed mechanism of sorption. The inversion of gradient of chemical potential upon the formation of delocalized particles determines the backward material flow.

The most important aspects of the large-tonnage synthesis of isotactic polypropylene represent a commercial secret. After polypropylene synthesis is completed, catalysts and other substances involved in the formation of the final product pass into the category of worthless and unknown impurities. This circumstance determines the peculiarities and difficulties of studying the behavior of impurities in polypropylene films. In this paper, the interaction of hydrophobic and hydrophilic probe liquids with polypropylene films (membranes) containing such impurities has been studied using pervaporation at different temperatures. The supramolecular structure of the polypropylene films has been successively modified by one- and two-sided hexane sorption. This procedure has decreased the apparent activation energy of permeability during pervaporation of water and acetone. It has been shown that, in the long run, the transmembrane convective pervaporation stream of acetone displaces hydrophobic and hydrophilic impurities from the polypropylene films.

In industrial synthesis of stereoregular polymers, substances such as multicomponent catalysts are known to contaminate a final product, thus becoming impurities to be removed from a polymer. Here, we show that liquid sorbates, when added to impurities inside a polymer, can be used as probes in studying the polymer’s prehistory of sorption and mass transfer. The main features of this process are described and discussed.

It has been shown that mesoporous nanocontainers from SiO2 may be obtained by the sol–gel synthesis using drug (Miramistin) micelles as a template. The nanocontainers resulting from the combination of the stages of their synthesis and loading are characterized by a very high content of the drug (no less than 0.9 g per 1 g of SiO2). The kinetics of Miramistin desorption from the mesoporous particles into an aqueous medium has been studied under static and quasi-dynamic conditions. The desorption has been shown to rather strongly depend on pH. Possible mechanisms of the desorption process have been discussed.

Chitosan films prepared by the thermal method from molding solutions containing ethanol as a chitosan precipitant have been used as separating membranes for pervaporation of an aqueous isopropanol solution. The flux density and permeate composition have been determined as functions of the composition of a molding solution and a solution to be separated, as well as the concentration prehistory of the separation process. The concentration prehistory reflects the specific features of swelling polymer sorbents, which are distinguished by a labile structure and macroscopic sorption deformations. The existence of a concentration prehistory implies that, at a fixed concentration of an initial solution, parameters characterizing the transport properties of a polymer depend on the process route in which this concentration has been achieved. The composition of a molding solution and the route of variations in the initial concentration of a solution to be separated that correspond to the highest value of our criterion for the process efficiency have been determined. It has been shown that, in the case of films formed from a solution containing 20 wt % ethanol, the water flux density reversibly increases by more than 100 times as compared with the flux density of a water-alcohol solution.

The sorption capacity of a polymeric pervaporation membrane for the target component can be substantially increased by its preliminary treatment with a substance having an increased affinity for the polymer. The key features of the sorption history have calculated from balance relations. It has been found that the flux of acetone during pervaporation through a polyamide-6 membrane modified by the preliminary sorption of water increased by an order of magnitude. The glass-transition temperature of the polyamide in water has been experimentally determined to be ∼50°C.

Transmembrane flux density may depend on membrane area, provided that the properties of the membrane vary with variations in the latter. This situation takes place for pervaporation processes realized with the use of chitosan films swelling in water-isopropanol solutions being separated. In this work, the flux density and permeate composition have been determined as depending on the composition of a molding solution containing a precipitant as one of its components, concentration of a solution being separated, and film area (2 and 20 cm2) in pervaporation setups. Irrespective of the composition of a molding solution, abnormally high flux densities of water and isopropanol, as compared with the flux density of a water-alcohol solution, take place for chitosan films with an area of 20 cm2. When the pervaporation is performed through a 2-cm2 film, all observed abnormalities disappear with the exception of the only one: the permeates is enriched with isopropanol in all experiments.

A new criterion is proposed for evaluating the efficiency of separation processes—the selective flux of a pure desired component, which includes both concentration changes and the productivity of a separation apparatus. An algorithm for calculating the proposed criterion is given, the concept of the efficiency coefficient is introduced, and its relationship with the degree of selective separation of a binary solution is demonstrated.