Vol 80, No 1 (2018)

Contemporary understandings of the physicochemical mechanism of diagenetic transformations in carbonate rocks have been reviewed. The transformations comprise the dissolution of stressed zones of the rocks with the formation of supersaturated solutions, mass transfer in the direction of the concentration gradient, and reprecipitation. Characteristic features of the mechanism, which make it possible to diagnose its effects on the results of petrographic observations and to simulate the process under laboratory conditions, have been discussed. Especial attention has been focused on applied aspects, which will stimulate further interdisciplinary studies performed at different scales.

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.

The diffusion deposition of point particles from a Stokes–Brinkman transverse stationary flow in a model monolayer membrane composed of contacting spherical hollow grains (capsules) with porous permeable shells formed from nanoparticles, is calculated. Monolayers with square and hexagonal packings of the grains are considered. Approximation equations are constructed for the dependences of grain drag force on shell thickness, Brinkman permeability parameter S, and internal shell radius ξ. Efficiencies of point particle collection on the grains are calculated as depending on the Peclet number, S, and ξ, and it is shown that layers of hollow permeable grains possess the highest filtration performance criterion among layers of impermeable and permeable uniform porous grains provided that the zero-concentration boundary condition is fulfilled at the outer radius of the grain.

The influence of different physicochemical parameters, such as particle concentration and size, droplet volume, dispersion medium composition, and substrate hydrophilicity, on the structure of deposits resulting from evaporating sessile droplets of colloidal dispersions has been studied. Parameters enabling one to targetedly control the structure of a deposit have been determined. The possibility of obtaining deposits having the shapes of thin rings and monolithic disks has been shown. The conditions have been found under which monolayer and multilayer deposits with ordered arrangement of particles are formed.

Since the aggregation number of micelles always grows with concentration, and, in some cases this dependence is noticeable even for spherical micelles, there is a need to revise the theory of micellization, in which the aggregation number is assumed to be constant. This work reformulates the theory of diffusion of nonionic surfactants in micellar solutions with regard to the variability of the aggregation number. A new formula, which expresses the diffusion coefficient of a surfactant via the diffusion coefficients of monomers and micelles, contains an additional factor capable of increasing the diffusion coefficient with the surfactant concentration. However, this factor is not overly strong, and the “old” part of the formula acts in the opposite direction; as a result, the conventional decrease in the diffusion coefficient of a nonionic surfactant remains prevailing. The analytical consideration has been supplemented with numerical calculations, the results of which are presented in the tables.

The effects of the composition and concentration of an external solution on the swelling degree of polystyrene-based ion exchangers crosslinked with different amounts of divinylbenzene have been analyzed within the heterophase model of polymer gel structure. It has been confirmed experimentally that, upon variations in the composition of the external solution, the swelling degree of polymers is determined by the content of “sorbed” water alone. Therewith, the volume of the external solution incorporated into the swollen polymer remains constant; i.e., it depends neither on an ionic form of an ion exchanger nor the concentration and composition of the external solution, but rather depends linearly on the polymer crosslinking degree. An algorithm has been proposed for calculating the volume of water in a polymer gel and some quantitative estimates have been presented.