Effect of Nanoparticles on Viscosity and Interfacial Tension of Aqueous Surfactant Solutions at High Salinity and High Temperature

Surfactant flooding has widely been used as one of the chemically enhanced oil recovery (EOR) techniques. Surfactants majorly influence the interfacial tension, γ, between oil and brine phase and control capillary number and relative permeability behavior and, thus, influence ultimate recovery. Additives, such as nanoparticles, are known to affect surfactant properties and are regarded as promising EOR agents. However, their detailed interactions with surfactants are not well understood. Thus, in this work, we examined the influence of silica nanoparticles on the ability of surfactants to lower γ and to increase viscosity at various temperatures and salinities. Results show that the presence of nanoparticles decreased γ between n-decane and various surfactant formulations by up to 20%. It was found that γ of nanoparticles–surfactant solutions passed through a minimum at 35 °C when salt was added. Furthermore, the viscosity of cationic surfactant solutions increased at specific salt (1.5 wt.%) and nanoparticle (0.05 wt.%) concentrations. Results illustrate that selected nanoparticles–surfactant formulations appear very promising for EOR as they can lower brine/n-decane interfacial tension and act as viscosity modifiers of the injected fluids.     

Hygrothermal aging of rubber‐modified and mineral‐filled dicyandiamide‐cured DGEBA epoxy resin. III. Dielectric spectroscopy investigation

The effects of moisture absorption on the dielectric properties of a rubber‐modified, mineral‐filled, epoxy resin based on the diglycidyl ether of bisphenol A cured with dicyandiamide are reported. Samples of the resin were aged by immersing in deionized water, or 5% w/w NaCl solution, at elevated temperatures. Dielectric measurements were carried out over the frequency range 10^?1 to 6 × 10⁵ Hz. A featureless dielectric spectrum was observed with both real and imaginary dielectric permittivity increasing with the amount of absorbed water. The change in the dielectric properties with absorption of water was independent of presence of salt, temperature of exposure, and aging history, although a hysteresis of the hydration–dehydration process was observed at low frequencies. Two types of absorbed water were observed—water molecularly dispersed within the epoxy matrix and clustered water in spherical microcavities. The time dependence of the real dielectric permittivity measured at 10 kHz was found to closely resemble that of the water absorption, which allowed the activation energy of diffusion to be calculated from both dielectric and gravimetric data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1011–1024, 2002; DOI 10.1002/app.10368     

Interaction of Silicate Melts with Hematite

The interaction of sintered hematite Fe₂O₃ with melts in the PbO–SiO₂ system at 900°C and melts in the Na₂O–SiO₂ system at 1150°C is investigated by the annealing–quenching technique with the use of standard physicochemical methods (X-ray powder diffraction analysis, scanning electron microscopy, quantitative X-ray microprobe analysis). The melting diagrams of the PbO–Fe₂O₃–SiO₂ and Na₂O–Fe₂O₃–SiO₂ systems are calculated and constructed on the basis of the model of regular solutions. An analysis of the experimental and calculated data demonstrates that the diffusion dissolution of hematite at the hematite–melt heterogeneous interface can be observed only for the PbO melt. For lead and sodium silicate melts, the diffusion process is accompanied by the concurrent redox reaction with the liberation of gaseous oxygen, which appreciably promotes the erosion of solid hematite.     

Comparative Effects of Deferiprone and Salinomycin on Lead-Induced Disturbance in the Homeostasis of Intrarenal Essential Elements in Mice

Lead (Pb) exposure induces severe nephrotoxic effects in humans and animals. Herein, we compare the effects of two chelating agents, salinomycin and deferiprone, on Pb-induced renal alterations in mice and in the homeostasis of essential elements. Adult male mice (Institute of Cancer Research (ICR)) were randomized into four groups: control (Ctrl)—untreated mice administered distilled water for 28 days; Pb-exposed group (Pb)—mice administered orally an average daily dose of 80 mg/kg body weight (BW) lead (II) nitrate (Pb(NO₃)₂) during the first two weeks of the experimental protocol followed by the administration of distilled water for another two weeks; salinomycin-treated (Pb + Sal) group—Pb-exposed mice, administered an average daily dose of 16 mg/kg BW salinomycin for two weeks; deferiprone-treated (Pb + Def) group—Pb-exposed mice, administered an average daily dose of 20 mg/kg BW deferiprone for 14 days. The exposure of mice to Pb induced significant accumulation of the toxic metal in the kidneys and elicited inflammation with leukocyte infiltrations near the glomerulus. Biochemical analysis of the sera revealed that Pb significantly altered the renal function markers. Pb-induced renal toxicity was accompanied by a significant decrease in the endogenous renal concentrations of phosphorous (P), calcium (Ca), copper (Cu) and selenium (Se). In contrast to deferiprone, salinomycin significantly improved renal morphology in Pb-treated mice and decreased the Pb content by 13.62% compared to the Pb-exposed group. There was also a mild decrease in the renal endogenous concentration of magnesium (Mg) and elevation of the renal concentration of iron (Fe) in the salinomycin-treated group compared to controls. Overall, the results demonstrated that salinomycin is a more effective chelating agent for the treatment of Pb-induced alterations in renal morphology compared to deferiprone.     

Unusual lipid composition of a Bacillus sp. Isolated from Lake Pomorie in Bulgaria

The lipid composition of a Bacillus sp., isolated from Lake Pomorie in Bulgaria, was unusual and consisted of 26 different fatty acids between C₁₂ and C₂₆, with anteiso C₁₅−C₁₇ saturated fatty acids predominating. The furan fatty acid, 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid, was also identified, a new finding for this genus. The hydrocarbons consisted of 30 different monounsaturated hydrocarbons, between C₂₅ and C₃₀, with the iso-iso, iso-anteiso, anteiso-anteiso, iso-normal, and anteiso-normal methyl branching for odd-numbered chains, and the iso-iso, iso-anteiso, iso-normal, and anteiso-normal methyl branching for even-numbered chains. The double bond positions in these hydrocarbons were determined by dimethyl disulfide derivatization followed by GC-MS, and the double-bond cis configuration was confirmed by infrared spectroscopy. Some previously unknown hydrocarbons in bacteria, such as (Z)-3,21-dimethyl-9-tricosene, (Z)-3,21-dimethyl-10-tricosene, (Z)-2,24-dimethyl-11-pentacosene, and (Z)-2,25-dimethyl-13-hexacosene were identified. Sterols were detected and were based on the sitosterol nucleus.     

The effect of the structure of the starting mixtures on the combustion of gas-generating compositions based on sodium azide

It is established that the combustion of mixtures of sodium azide with aluminum oxide and potassium dichromate at the lower limit for the dichromate content occurs in a chaotic self-oscillatory regime. Modification of the structure of the starting mixture by increasing the dichromate particle sizes from 40–60 K to 250–500 μm lead to significant stabilization of its combustion parameters. The amount impurities and aerosols in generated nitrogen is considerably decreased by reducing the energy content of sodium azide based composition. Using the relay-race model of combustion of heterogeneous systems, it is shown that, under the given conditions, the burning rate of such compositions is determined by the time of heating of potassium dichromate particles to the ignition temperature by neighboring burning particles. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 72–76, November–December, 2008.     

FTIR Characterization of Fe3+–OH Groups in Fe–H–BEA Zeolite: Interaction with CO and NO

Fe³⁺–OH groups of a Fe–H–BEA sample prepared by conventional ion-exchange method are characterized by an IR band at 3686–3684 cm^?1. They exhibit a weak acidity: upon low-temperature CO adsorption the O–H stretching modes are blue shifted by 100 cm^?1 and the respective carbonyl adducts are observed at 2158 cm^?1. The Fe³⁺–OH groups are reduced at room temperature by NO to form Fe²⁺–NO species and NO⁺ groups in cationic positions. Desorption of pre-adsorbed NO at temperatures above 373 K regenerates the Fe³⁺–OH groups. The relation of the Fe³⁺–OH species to the so-called α-oxygen is discussed.     

Electrodeposition of PbSe onto n-Si(1 0 0) wafers

PbSe was electrodeposited onto monocrystalline n-Si(1 0 0) wafers from 50 mM Pb(NO₃)₂ + 2 mM SeO₂ + 0.1 M HNO₃ solution. The mechanism of PbSe electrocrystallization on n-Si was studied. At initial stage, 3D Pb and 3D Se nuclei are simultaneously codeposited onto Si at potentials more negative than Si flat band potential and chemically interact resulting in PbSe formation. When n-Si/PbSe heterostructure is formed, the overvoltage of bulk lead deposition increases, as a result of redistribution of electrode potential. Further growth of PbSe is realized due to underpotential deposition (UPD) of Pb and overpotential deposition (OPD) of Se onto formed PbSe nuclei. With Pb UPD shift increase, amorphous Se inclusion is registrated in the deposit. When 2D Pb nucleation mechanism is changed to 3D mode, metal Pb cubic phase is codeposited with PbSe. Electrodeposition of PbSe onto n-Si is irreversible. PbSe anodic stripping does not take place in the dark due to the barrier on solid interface. Oxidation of PbSe on n-Si is observed only under illumination, when photoholes are generated in silicon substrate.