A method is proposed for a priori calculating adsorption isotherms based on the combination of the molecular dynamics method and Dubinin-Radushkevich and Tolmachev-Aranovich equations. The isotherms of adsorption of individual gases and vapors, as well as components of gaseous and vaporous mixtures and liquid solutions on microporous active carbons, are calculated using this method.
A numerical solution of the problem of the kinetics of the decrease in surface tension, taking the dependence of the concentration of nonomeric surface-active ions and counter-ions on the surfactant concentration into account, was performed on the example of micellar solutions of sodium dodecyl sulfate. It was shown that at a surfactant concentration exceeding the critical micelle concentration by one to two orders of magnitude, the rate of decrease in the surface tension may be reduced in comparison with substantially less concentrated micellar solutions.
An experimental study is made of flows which develop in the neighborhood of electrically conducting spherical particles in distilled water when acted upon by a variable external electric field. It is established that the character of the flow depends on the parameters of the field and particle size. One reason for the creation of the flow is the quadratic (with respect to the field) effect of electroosmotic motion of the fluid over the particle surfaces. This motion is due to the generation of free polarization charges at the phase boundary. Empirical relations are obtained to describe the dependence of flow velocity on the strength and frequency of the electric field.
The micelle formation of fluorocarbon surfactants: ammonium salts of perfluoroacids - perfluoroenanthic, perfluorocaprylic, perfluoropelargonic, and 2,5-dimethyl-3,6-dioxanonanoic acids - in aqueous and aqueous-organic solutions was investigated. The free energy, enthalpy, and entropy of micelle formation were calculated. It was shown that the nature of the surface tension isotherms is determined by two competing processes: structure formation in the volume of the solution and its adsorption on the interface. A F-19 NMR study was made of the interaction of surfactants with the organic phase. An anomalous decrease in the surface tension of an aqueous solution of fluorocarbon surfactants was detected with additions of water-soluble organic liquids were introduced. A scheme is suggested for the interaction of surfactants with dimethylformamide. The anomalous decrease in the surface tension when "microadditives" of aqueous-organic liquids are introduced is explained by compaction of the surfactant layer and an increase in the adsorption.
The dielectric constant of the polyethylene glycol monoalkylphenyl ethers OP-4 and OP-10 and fractions of OP-10 at frequency of 1.16 MHz and the low-frequency dielectric-loss spectra in the range of frequencies from 20 kHz to 50 MHz and at 9.37 and 37.5 GHz have been studied. The dependence of the dielectric properties of the samples studied on the degree of oxyethylation and the distribution of the polymer homologs has been established.
A correlation between the degree of ionization (alpha) of the ionogenic groups at the point of zero charge (PZC) and the aggregative stability of aqueous dispersions of oxides under the conditions of the PZC has been demonstrated. An hypothesis regarding the relationship between alpha (under the conditions of the PZC) and the thickness of the boundary layers of water has been advanced.
The viscosity of a dilute colloidal gel formed by lyophobic quartz particles was found to decrease by a factor of 10(9) when the shearing stress-sigma exceeded a critical value sigma(c). With (1) sigma < sigma(c), or (2) sigma > sigma(c), the values of the system viscosity eta-1 and eta-2 almost-equal-to eta-1/10(9) were very little dependent on sigma within the range studied. Values of sigma(c), eta-1, and eta-2 agreeing with the experimental values have been obtained theoretically on the basis of concepts of a fractal structure of dilute aggregates and gels. It has been concluded that at sigma = sigma(c), the system must be inhomogeneous and should separate into phases that are characterized by viscosities eta-1 and eta-2 and rates of shear sigma(c)/eta-1 and sigma(c)/eta-2.
Based on scaling estimates, it was concluded that the viscosity of colloidal systems increases anomalously in approaching the critical point of the sol-gel transition. The hydrodynamic vicinity of the critical point in which the Ornstein-Zernike equation holds was studied.
The disadvantages of the generally accepted method of graphic calculation of the shear moduli of disperse systems were pointed out. The absence of regions of invariance of the shear moduli of aqueous dispersions of Aerosil, graphite, and palygorskite was established in studying the structural-mechanical properties with a Weiler-Rehbinder setup with a differential-transformer motion transducer. The method proposed, for obtaining the structural-mechanical constants characterizing the characteristics of unperturbed structures and for better reproducibility of the results obtained with instruments of different sensitivity, is graphically extrapolating the shear moduli of the systems studied to zero stress.
The dielectric constants epsilon(s) of isononylphenol, of laboratory and industrial samples of ethoxylated AF9-n isononylphenols (where n = 3-12 is the number of ethylene oxide groups), and of their German NOP-grade analogs (where n = 10-18) have been measured at the frequency 1.16 MHz. The value of epsilon(s) increases with the degree of ethoxylation only at n less-than-or-equal-to 6 and then remains constant. At equal values of n the dielectric constants of different series of AF9-n and NOP samples are different. The dipole moments of AF9-n molecules in the liquid phase increase with increasing n in the entire interval of n = 3-18 studied.
The influence of surfactants on the viscosity and surface tension of solutions of carbohydrates, Na-CMC and polysaccharides, was studied. It was shown that the conformation of the macromolecules in solution and their adsorption power at the water/air interface depend substantially on the intensity of the ionic interactions between the polymer and the surfactant molecule. The adsorption constants of surfactant-polymer complexes were calculated, and their relationship to the hydrodynamic characteristics of the macromolecules were demonstrated.
A model showing the correlation between the interparticle interaction and viscoelastic properties of different media was obtained by summation of the stress tensors, which are a function of the velocity gradient and coordinates, with subsequent expansion of the stress tensors with respect to the degrees of the strain tensors and velocity gradient tensors.
The variation of the ultimate static shearing stress (P(S)) of the complex of carbamide with n-heptane as a function of the ratio of the mass of the dispersion medium to the mass of the dispersed phase (chi) and the ratio of the height of the stationary layer of the system to its diameter (psi) has been studied experimentally. The decrease in P(S) as chi is increased and psi is diminished has been described mathematically.
A method is proposed for solving equations of the theory of inhomogeneous fluids. The method is based on expansion of unary and binary thermal potentials into a series in the dipole-dipole interaction parameter. Such an approach makes it possible to explicity determine the orientation dependence of the unary correlations function. The singlet approximation is used to obtain analytic solutions to the equations for solid dipole spheres in the low-density
The structure of micelles of cationic surface-active monomers, formed in the region of the critical micelle concentration CMC-2 in water, was investigated using a broad spectrum of physico-chemical methods. It was found that anisotropic micelles, the monomer molecules in which are packed in layers, with an interplanar distance close to two lengths of the aliphatic portion of the molecule, are formed in this region. In comparison with the primary micelles, the secondary micelles are characterized by greater ordering of the microstructure, a greater degree of binding of the counterion, and less molecular mobility. This, together with a definite mutual arrangement of the latter, prevents radical polymerization of the monomer in secondary micelles.
Experimental studies were made of stationary flows of liquid which develop in the vicinity of spherical particles of ion-exchange resins under the influence of a variable external electric field. The spatial distribution of the flows near particles is determined along with the dependence of fluid velocity on the parameters of the field. The magnitude of the effect is proportional to the square of field strength. Differences are seen in the behavior of flows for the cationites and anionites under different experimental conditions, which indicates the existence of differences in the mechanisms responsible for such flows in these cases.
The radical polymerization of cationic surfactant molecules in their micellar solutions in water and toluene was investigated. A correlation of the kinetic characteristics of polymerization with the type of monomer micelles was established. It was shown that the change in the maximum conversion and rate of polymerization of the monomer as a result of the change in its structure, concentration in the system, and nature of the additive introduced reflects a change in the microstructure of the micelles under the influence of the indicated factors. It is concluded that measurement of the kinetic parameters of the polymerization of micelle-forming monomers can be an informative method of investigating micellar structure.
The movement of a group of bubbles in a non-Newtonian fluid was investigated. The equations for the bubble floating velocity in the range of modified Reynolds numbers from 0 to 1500 were obtained.
Outflow of an aqueous solution and separation of oil in the form of an emulsion from a foam emulsion and breaking of the foam emulsion as a disperse system as a whole (i.e., a reduction in the column height) were investigated. The most stable foam emulsions with respect to separation into foam and emulsion were obtained with higher volume fractions of oil (>0.8) in the starting O/W emulsion.
The surface tension of systems of aqueous gelatin solution's with additions of organofluorine surface active substances (FSAS) is studied at 313 K. In the work anionic FSAS (AFSAS) - a mixture of alpha-(heptafluoropropoxy)-omega-(tetrafluoro-2-propanoic acid)-poly[oxy(1,1,1,2,3,3-hexafluoro-1,2-propanediyl] oligomers, cationic FSAS (CFSAS) - a mixture of the chlorides of oligomeric N-3-(N'-acyl)aminopropyl-N-(2-hydroxyethyl)-N,N-dimethyl ammoniums where the acyl group is alpha-(heptafluoropropoxy)-omega-(tetrafluoro-2-propanoyl)-poly[oxy(1,1,1,2,3,3-hexafluoro-1,2-propaneydiyl], and nonionic FSAS (NFSAS) - a mixture of bis(2-hydroxyethyl) amides of alpha-(heptafluoropropoxy)-omega-(tetrafluoro-2-propanoic acid)-poly[oxy(1,1,1,2,3,3-hexafluoro-1,2-propanediyl] oligomers. Small additions of the organofluorine compounds in concentrations below the CCMF [critical concentration of micelle formation] to aqueous solutions of gelatin lower the surface tension of the solutions. The relaxation periods and surface activity of the gelatin macromolecules at the air/solution interface are determined. A 2-10-fold decrease in the relaxation periods of protein macromolecules and a 2-2.5-fold increase in the surf ace activity are found in the presence of FSAS. The results of the investigation make it possible to give a colloid chemical basis for the use of photographic surfactants in the manufacture of motion picture film.
