N. A. Ivanova

Method of obtaining structured hydrocarbon gels for increasing the efficiency of oil spill recovery technologies

It was found that lithium tetraalkoxyborates are highly efficient gelling agents for hydrocarbons. The viscosity of liquid hydrocarbons can be increased to a desired degree by mixing them with a gelling composition of lithium tert-butoxide Li-O-C(CH3)3 and trialkoxyborate B(OC8H17)3 in equimolecular amounts. Oil gelled by this composition has a rubberlike consistency, which retains its shape; therefore, oil spills treated with the use of this method can be more efficiently recovered mechanically or by hand.

An analysis of absorption-desorption of volatile organic compounds by molecularly imprinted polymer films

A theoretical analysis of the experimental data on absorption (desorption) of volatile organic compounds by (from) molecularly imprinted polymer films was performed. The theoretical time dependences of the amount of absorbed analyte in a film were calculated using a system of equations with four kinetic parameters (Γ, K, Ksur, and Ceq), which were determined by theoretically approximating the experimental data. The special features of the absorption-desorption process in a polymer film were suggested to be described using a parameter called the specificity coefficient. Specificity coefficients were determined for all the polymers and analytes studied. The specificity coefficients obtained from the chromatographing data were compared with the imprinting factors of chromatograms calculated from the experimental retention time values. An empirical linear dependence of specificity coefficients on imprinting factor values was obtained.

Dynamic adsorption of nitrogen dioxide on zeolites

The dynamic adsorption of nitrogen dioxide on Zeolon 900H, Zeolon 900K, Zeolon 900Na, Zeolon 200H, Zeolon 500H, H/ZSM-5, Na/ZSM-5, and CaA zeolites is studied. Breakthrough curves C/C0 = σ(t) (C0 is the initial concentration of NO2 at the adsorption column inlet and C is the breakthrough concentration at the column outlet) is measured over a temperature range of 290–430 K. It has been shown that the time dependence of C/C0 is described by the Wheeler–Jonas equation. The parameters of this equation, the adsorption constant rate kv and dynamic adsorption capacity (DAC) are determined by fitting the theoretical curves to the experimental data for the aforementioned zeolites at 290–430 K. The Hertz–Knudsen equation is used to obtain theoretical temperature dependence of kv. For this dependence, the curve fitting method is also used to determine the adsorption activation energy Ead. It is found that the activation energy ranges within 300–500 cal/mol, which shows that the adsorption of NO2 on these zeolites is a physical process, with the electronic structure of the molecules being perturbed only slightly during the adsorption process. A theoretical formula for calculating the time of protective action of the sorbent is derived. It is shown that the DAC and the corresponding protective action time for the studied sorbents depend on the temperature and increase in the series Zeolon 900Na < Na/ZSM-5 < Zeolon 900K < H/ZSM-5 < Zeolon 500H < Zeolon 200H < Zeolon 900H for gas mask filters at room temperature (293 K), and increase in the series CaA < H/ZSM-5 < Zeolon 900H < Zeolon 500H < Na/ZSM-5 < Zeolon 200H < Zeolon 900K < Zeolon 900Na for systems of purification of flue gases from thermal power plants at 350 K.

Analysis of space–time profiles of the concentrations of contaminants in soil during electrokinetic remediation

A new semiempirical method for the mathematical description of the space–time concentration profiles of contaminants in soil during its electrokinetic remediation is proposed. The method is based on approximating the experimental data on the spatiotemporal behavior of the concentration, C = C(Da, t). The experimental and theoretical C = C(Da, t) dependences reported in the literature and obtained in our studies were approximated by seventh order polynomials. For example, the space–time concentration profiles of chlorinated hydrocarbon contaminants in unsaturated soils, such as tetrachloroethylene, trichloroethylene and carbon tetrachloride, have been successfully described by a polynomial function with determination coefficients of R2 = 0.9941, 0.9988, and 0.9972, respectively. A pilot test setup for studying the electrokinetic remediation of soils contaminated with mercury compounds, with ten sampling sections and replaceable cartridges with ionites, was designed and built. This setup allowed measuring the space–time concentration profile of mercury in soil samples during electrokinetic remediation. This profile obtained was approximated by a seventh order polynomials with a determination coefficient of R2 = 0.9929. It is shown that the polynomial approximation of the space–time concentration profiles of contaminants in soil describes the experimental C = C(Da, t) dependences no worse (sometimes better) than the Poisson–Nernst–Planck model for ionic flow.

A study of the distribution of the concentration of mercury ions along a fixed ionite bed in the sorption treatment of water

A new approach to the mathematical description of the breakthrough curve by using the space−time concentrations profile of contaminants along the fixed sorbent bed in the process of sorption purification of water is proposed. For the breakthrough concentration C of contaminant in water effluent from the fixed bed, an expression for its time dependence is derived. The space−time concentration profile of mercury adsorbed from a polluted water flow on Amberlite® GT-73 cationite was determined experimentally. Using the formula derived in the present paper, the time dependence C(t) is calculated, known as a breakthrough curve. The latter was compared with a curve determined experimentally using traditional methods. A close match between the two curves is observed. It is established that, during the adsorption process, adsorbed mercury ions are redistributed between different parts of the fixed bed. It was found that, up to the time of breakthrough (200 min), the concentration of mercury in water flowing out from the fixed Amberlite® GT-73 bed, ranges within 1−5 μg/L, i.e., is below the maximum permissible concentration, even if the incoming water contains mercury in a concentration of up to 70 mg/L, which corresponds to the typical level of pollution of industrial wastewater.

A study of the oxidation of ultrafine powder of activated aluminum with water to form an IR-opaque aerosol

The reaction of oxidation of ultrafine powder of activated aluminum (UFPAA) with water is studied. Activated aluminum is meant to be a juvenile aluminum powder coated with a water-soluble polymer film (polyethylene oxide). When exposed to water, the polymer film dissolves, allowing metallic aluminum to react with water. A method of preparation of UFPAA using a ball mill is described. The reactions of UFPAA with water in closedand open-type reactors are investigated. For the closed-type reactor, the effect of the initial amount of UFPAA and of the Al-to-H2O ratio on the temperature and pressure of the process, as well as the composition of the solid and gaseous reaction products, are determined. It is found that, at a UFPAA sample weight of ≥100 g, the temperature and pressure of the reaction increase above the critical values for water (T = 374.2°C, P = 22.14 MPa). The open-type reactor is demonstrated to produce aerosol. It is shown that, the reaction of 100 g of initial UFPAA with water at Al-to-H2O ratios ranging from 1: 1 to 1: 5 produces aerosol particles containing aluminum in concentrations CAl from 13 to 18 wt %. The dependence of the masking ability of aerosols (MΔλ) in the IR region of the electromagnetic radiation (Δλ = 3–14 μm) on CAl is measured. The MΔλ(CAl) dependence is a monotonically increasing function, with the maximum, MΔλ = 1.9 m2/g, reached at CAl = 18 wt %.

The use of macrocyclic polyethers for promoting the dry cleaning of the surface from radionuclides

The cleaning of the stainless steel surface from 137Cs and 90Sr ions was studied by the peelable polymer film method. An extracting solution of polyvinylbutyral in dioxane containing various crown ether additions to increase the efficiency of extraction was spread over the surface. A polymer film formed on the surface as a result of solvent evaporation from the extracting solution. After the extraction, the polymer film containing radionuclides was removed and utilized. The extraction of 137Cs and 90Sr ions from neutral aqueous solutions with AN-221 and AN-511 anionites modified with crown ethers was studied. The distribution coefficients were shown to increase in the series 12-crown-4 < 18-crown-6 < dicyclohexyl-18-crown-6 < 15-crown-5 for the extraction of 137Cs and in the series 15-crown-5 < dicyclohexyl-18-crown-6 < 18-crown-6 < 12-crown-4 for the extraction of 90Sr. The structural characteristics of the Cs and Sr complexes with crown ethers taken from the Cambridge Structural Database (2013 Release) were compared with the data on the extraction of 137Cs and 90Sr ions from aqueous solutions. The distances between the two complexing atoms (O-Cs or O-Sr) decreased as the corresponding distribution coefficients increased. The dependences of the residual radioactivity (137Cs and 90Sr) on the number of depositions/removals of the polymer film on/from the surface were measured for different crown ethers. When crown ethers were added to the extracting solution (polymer film), the efficiency of decontamination increased by two orders of magnitude. The most effective additions were dicyclohexyl-18-crown-6 and 15-crown-5 for 137Cs and 12-crown-4 for 90Sr. After three treatments of the surface with solutions (polymer films) with these additions, its radioactivity was close to background.

Application of sorbents to the collection of crude oil and refined product spills

The adsorption of oil and refined products by polyurethane foams was studied. The dependence of the specific surface area of polyurethane foam specimens on the specific weight was determined. It was found that this dependence is described by a monotonically decreasing exponential curve in the test range of specific weights. The dependence of the sorption capacity of polyurethane foam specimens on specific surface area was measured for gasoline, diesel fuel, crude oil, industrial oil, and fuel oil. It was found that the dependence is described by increasing curves with small scattering of experimental data points. The regeneration of polyurethane foams saturated with hydrocarbons was also investigated. The effect of the number of sorbent regeneration cycles on the sorption capacity of polymer foam specimens was estimated. It was found that polyurethane foams with specific weights of 0.020–0.022 g/cm3 and specific surface areas of 0.063–0.074 m2/g are the most suitable materials for oil and refined product spill recovery.

Colorimetry: Choice of colorimetric parameters for chromophore concentration measurements

The problem of choice of tristimulus color coordinates which uniquely depend on chromophore concentration in an investigated material has been considered. A theoretical study shows that there are no simple analytical formulas for such dependences, and the majority of tristimulus coordinates of various color spaces: RGB, CIE (XYZ), CIE (L*a*b*), CIE (L*C*H*), HSB, and CMYK poorly correlate with the concentration of molecules responsible for color. However, analysis of published papers on this subject provides abundant evidence showing that at least one tristimulus coordinate of the CIE (L*a*b*) color space, specifically L* (lightness), is related to chromophore concentration C by a simple, steadily descending exponential function. The empirical formula L* = L*(C) can be successfully applied for instrumental treatment of experimental colorimetric data for the determination of chromophore concentrations.

The Effect of Selective Absorption Sites in the Diffusion Processes in Polymer Films

The mechanism of diffusion of analyte molecules in polymer films is studied. Equations in partial derivatives are derived for the description of both diffusion and adsorption of molecules in the polymer film containing sites of specific absorption. The kinetic parameters that characterize the specificity of adsorption sites are established. A theoretical approach is applied for the analysis of the experimental data on the diffusion of some volatile organic compounds in films based on molecularly imprinted polymers.