Presence Of Surface-active Substances Research Articles

Bubble Formation and Motion in Liquids—A Review

In flotation, a bubble acts as a carrier for attached particles. The properties of the gas–liquid interface of the bubble are one of the main factors determining the bubble motion and flotation efficiency. Monitoring of the bubble motion may deliver interesting information about the state of the gas–liquid interface. In the case of pure liquids, a bubble surface is fully mobile, while the presence of surface-active substances (e.g., surfactants) causes diminishing bubble velocity due to the retardation of the interface fluidity. The theoretical prediction of the terminal velocity value for the bubble has been investigated for over a century, delivering a number of various models describing bubble motion in a liquid. This narrative review is devoted to the motion of the bubble in stagnant liquids and is divided into three main sections describing: (i) experimental techniques for tracking bubble motion, (ii) bubble motion and shape deformation in clean water, and (iii) bubble motion in solutions of surface-active substances.

Strength of cellular concrete as a function of density under axial uniaxial compression

The purpose of this work is a comparative analytical assessment of the axial compressive strength of foam concrete depending on its density grade, taking into account strength losses in the presence of surface-active substances, porosity, and strength characteristics of the matrix material. The values specified in GOST 25485-89 and calculated according to the proposed analytical laws and regulatory data are compared. The effect of the foaming reagent on the strength of the foam matrix was evaluated in accordance with GOST 30744-2001 on standard samples-beams 40x40x160 mm in size from the control cement test without additives and with additives of synthetic and protein foaming agents of different concentrations in the sealer (from 0.3 to 3%). The degree of influence of the foaming agent on the strength of the finished foam concrete prepared using classical technology was performed on samples-cubes of 100x100x100 mm in size according to GOST 10180-90. The article presents the results of a study of uniaxial compression strength calculated for cellular concrete depending on the density grades known from these regulatory documents and other sources. Analytical expressions for determining the strength calculated for cellular concrete with an average density of 300-900 kg/m3 are presented. The proposed approach, based on the assessment of the initial data – the strength class of the binder, porosity, matrix strength, type and concentration of the foaming agent-allows us to predict the final strength of foam concrete products of this average density. Their rational accounting will help in the production of construction products of the maximum possible strength at a given density. This will expand the use of foam concrete in construction.

Intensifying the process of methane gas hydrates crystallization in the presence of surface-activated substances

The crystallization process of gas hydrates during their formation in the presence of surface-active substances (SAS) is studied. The research is conducted in two directions – theoretical and experimental. Experimental data on the crystallization rate of methane gas hydrates formation in the presence of surfactants have been obtained: high-molecular compounds are used on the basis of polymeric quaternary ammonium salts containing side aliphatic radicals of various lengths in the acyl fragment, as well as a number of specific surfactants. The process of methane gas hydrates formation is performed using a laboratory setup of the NPO modification for the gas hydrates creation. To analyse the experimental data, technical and metrological instruments are used: stalagmometric method with automatic photoelectric drop counting, conductometric method, Wheatstone bridge, spectrophotometric titration of amino end-groups, viscometer VPZh-1. It has been substantiated that the crystal formation rate depends on the surfactant concentration. New experimental dependences of the gas hydrates formation on surfactants under thermobaric conditions in the presence of surfactants have been found. It has been revealed that the crystallization process during the methane gas hydrates formation is accelerated in the presence of a surfactant. As a result of their application, the effect of solubilization and catalysis arises with the formation of the so-called “diffusion zone”, the size of which decreases in the presence of surfactants, thereby accelerating the substance transfer to the surface on which crystallization occurs. An increase in the surfactant concentration leads to an increase in the rate of molecular diffusion, and also creates a more intense turbulent diffusion.

Morphological and Structural Changes in Titanium Dioxide during the Fragmentation Process

The structural and morphological changes of titanium dioxide particles in the process of ultrafine fragmentation have been studied by means of the X-ray diffraction analysis and BET method based on N2 adsorption-desorption. The sizes of crystallites and microdeformations that indicated a breakage of their structural order with the formation of new phase fragments similar to brookite have been calculated from broadening of diffraction reflections using the method of approximation applying the pseudo-Voigt function. In the study of the morphology of titanium phase particles, it was determined that nitrogen adsorption was described by the isotherm of the IVa type in the p/p0 range of 0.1–0.95 and by the isotherm of the II type at p/p0 higher than 0.95 after mechanical activation in the presence of surface-active substance (SAS). The hysteresis loop of the samples' isotherms is related to the H3 type, which is characteristic of particles with a lamellar morphology. The porous particle system was represented by mesopores of a diameter varying within the range of 20–50 nm. The total volume of micropores was not higher than 10% of their total volume. A monophase product with a rutile structure and the crystallites' size increase was formed from the activated sample at annealing. The specific surface area of titanium dioxide after annealing varied in the range of 6.5–7.5 m2/g, which is about three times higher than the same value for conventional rutile grades.

The comparison of cleaning and remineralizing properties of toothpastes with and without surface-active substances

Objective : Analysis of surface-active substances (SAS) effect on cleaning properties of toothpastes and remineralizing potential of saliva. Methods : We have assessed clinical indices as well as biochemical and microbiological parameters of oral fluid when using toothpastes with and without SAS. Results : Statistically significant changes when using various toothpastes by the 28th day were registered only for simplified oral hygiene index. The presence of SAS in the composition of toothpastes did not affect the total number of microorganisms in the composition of dental plaque (in the change in the number of individual species). There were no significant differences in the saturation of the oral fluid with Ca 2+ and PO 4 3– ions. Conclusions : SAS (sodium lauryl sarcosinate) using in toothpastes composition has a significant effect on cleaning properties of oral hygiene products while not having a special effect on the mineralizing potential of saliva.

ON THE PRODUCTION OF LECITHIN FROM SUNFLOWER OIL PHOSPHATE

The article discusses the multistage technologies of obtaining food lecithin using high temperatures. As a result of the work, food lecithin from phosphatide concentrate of sunflower oil using acetone and ethyl alcohol was obtained. The effect of hydrogen hydroperoxide on the phosphatide concentrate and on the properties of the resulting lecithin was investigated. t was established that the lecithin obtained from the phosphatide concentrate in terms of its physicochemical properties meets the requirements of the SDA 15.4-37-12: 2004. The infrared spectrum of lecithin, confirming the presence of functional fragments that are characteristic of food lecithin, was determined. Studies of solutions of lecithin have shown that the resulting product exhibits surface activity forming associates with a critical concentration of micelle formation ≈ 2%, reducing the surface tension, including in the presence of surface-active substances. In the future, the experimental data obtained will be used to develop a technology for the production of food lecithin. It is assumed that these studies will introduce a new technology in the chemical industry of the national economy.

Sorption of triclosan by carbon nanotubes in dispersion: The importance of dispersing properties using different surfactants

The production of carbon nanotubes (CNTs) increased rapidly due to the superior properties and was suggested to be the potential sorbents for environmental remediation. CNTs tend to form aggregates, thus CNTs dispersion was commonly produced by sonication with surfactant in industry for better application. In the present study, a novel passive sampling method was used to systematically study sorption of triclosan to CNTs dispersion to give a better understanding on their interactions especially with the presence of surface-active substances. With the increase of anionic surfactant concentration (SDBS or SDS), sorption of triclosan was gradually suppressed. CNTs dispersed by nonionic surfactant TX-100 increased or decreased sorption at different TX-100 and triclosan concentration. Little amount of cationic surfactant CTAB(1 mg/L) could sharply decrease triclosan sorption to CNTs but with larger CTAB concentration, sorption was continually increased. Sorption isotherms of triclosan to CNTs dispersion with 40 mg/L and 100 mg/L surfactant fitted well with Toth model show the existence of double competition in the sorption process. Different from the adsorption mechanism of previously aggregated CNTs and compounds. Sorption data combined with comprehensive characterization of CNTs dispersion and theoretical analysis, three effects referring to charge, dispersion and competition were proposed. Sorption coefficient was linearly correlated with the characterization parameters. Surface charge, dispersion status and surfactant concentration play the important role on triclosan sorption in CNTs dispersion in the presence of anionic, cationic and nonionic surfactant, respectively. The results provide basic supports on application of CNTs in remediation area and exploring the fate of both CNTs dispersion and pollutants.

Study of the formation mechanism of gas hydrates of methane in the presence of surface-active substances

The process of hydrate formation of methane in the presence of SAS in the temperature range of 274‒281 K was examined. The aim of the research conducted was to establish the effect of SAS on the process of GH formation, as well as to study kinetic features of their formation in the three-phase system “gas”‒”water+SAS”→”solid body (GH)”. We applied a stalagmometric method with automated photoelectron counting of drops (measurement error is 0.1 %), a conductometric method, with electrical conductivity measured using the Wheatson bridge (measurement error is 0.05–0.1 %). Interphase electric potential was measured by a potentiometric method using the potentiometer PPTV 1. Based on an analysis of the isotherms, by the indicators of surface tension of the aqueous solutions of SAS, we plotted isotherms of surface tension in the logarithmic –lgС SAS coordinates. The isotherms in the region of low concentrations demonstrate a curvilinear section, on which, in accordance with the Gibbs equation, adsorption at the interphase boundary increases with an increase in the concentrations. The curvilinear section of the isotherm passes into a straight line; in this case, the adsorption reaches its maximum value. Based on kink of the isotherm, we determined the value of CMC, which corresponds to the concentration of SAS equal to 1.75–2.00·10 -2 mol/l. The addition of SAS leads to a decrease in the magnitude of CMC. While studying the mechanism of hydrate formation of methane in the presence of SAS, it was discovered that the hydrate formation mechanism includes the following stages: micellization and solubilization. However, an increase in the volume of absorbed methane in the presence of SAS, as well as the activation effect, indicate the micellar catalysis. It is shown that the presence of SAS increases the amount of gaseous methane in GH by several times, as well as improves its quality (friability).

OPTIMIZATION OF MODIFYING MATERIAL DISTRIBUTION DURING LASER PROCESSING OF THE METAL SURFACE

The improvement of operational properties of metal parts during the laser surface treatment can be obtained by modifying the melt with the prepared nano-sized particles of refractory compounds (carbides, nitrides, and others.). It allowsthe number of crystallization centersto be increased, the structure to be grinded and the uniformity of the solidified metal to be raised. It is known that thermocapillary convection promotes the homogeneous distribution of materials penetrating into the molten metal. It is also known that the presence of surface-active substances in the melt influences the character of convection. There is evidence that the structure of flow in the melt depends on the amount of surface-active substances in the metal. Therefore, the studies were conducted to obtain data on the relationship of characteristics of metal processing by laser and the uniformity degree of modifying additives distribution. Using the numerical modeling the effects of characteristics of pulsing laser action on allocation of modifying particles are estimated at the presence of surface-active substance in metal. With the help of mathematical proposed model the following non-stationary processes are considered: heating and melting of the metal, heat transfer in the melt, fluid motion, nucleation and growth of the solid phase after termination of the pulse. During the numerical realization of the model the heat conduction equation was firstly solved. Upon appearance of molten metal the boundary of the liquid phase was determined. Further the coupled equations of convective heat transfer and motion of an incompressible fluid were solved. After the laser pulse termination, the calculations are continued until the complete solidification of the substrate material is achieved. It was supposed that modifying nano-sized particles under the influence of convective flows penetrate into depth of a melt from its surface. The movement and distribution of particles in a fluid was modeled using markers. The movement of the markers was determined by the local velocity of the melt. According to the results of numerical experiments, the effect of the parameters of pulsed laser action on the nature of the flow and distribution of the particles in the melt were determined. Optimum parametersfor the melting of the metalsubstrate by a laser pulse are proposed for various surface-active substances concentrations.

Faradaic and Capacitive Current Estimation by DPV-ATLD

In this work we for the first time proposed an approach based on ATLD which enabled exploration of the faradaic and double-layer charging current components in voltammetric experiments in the presence of surface-active substances. For simulated data ability to successful decomposition of the signals was confirmed and theoretic shape of two original components was restored. Next the proposed approach was applied in determination of Pb(II) in the presence of the increasing CTAB concentration. Considering calibration set of Pb(II), sampled with frequency of minimum 1 kHz, it was proved that total current may be effectively separated into two components. Capacitive current in the case without CTAB addition was ca. 15% higher in comparison with the case when 2 or 4 mgL−1 of CTAB was present, but decreased faster, and after 20 ms it reached the same value. Faradaic current decreased significantly with CTAB addition but the linear relation with depolarizer concentration was preserved. The calibration models were defined omitting the separated capacitive current component, what improved analytical parameters of the method. Using sampling period of 3 to 6 ms from the potential change, the sensitivity increased 2.7-3 times (depending on the CTAB concentration) in comparison with the typical interpretation, detection limit was also lower and reached 0.2–0.4 μgL−1 of Pb(II). For each concentration of CTAB the correlation coefficient r in lead determination was greater than 0.9970, while the repeatability expressed by the coefficient of variability was lower than 3%.

The current understanding of growing metallic filamentary crystals in an electric field

The existing ideas about one of the non-traditional methods of growing metallic filamentary crystals, such as growing in an electric field were considered in the paper. The role of impurities in the crystal growth process was investigated. Positive and negative sides of the electrolysis process during growing this group of crystals were critically considered. The experiments have shown that concentrated solutions of salts of several metals are the most suitable for growing filamentary crystals of metals and the presence of surface-active substances (SAS), having long molecules in the solution, is necessary for the nucleation of metallic filamentary crystals. The growth of metallic filamentary crystals is promoted by the presence of fine particles of graphite, glass and other mechanical impurities, and the presence of oxygen, on the contrary, retards it. During the formation of the whiskers of solder materials on thin-film electro-resistances when passing an electric current through them, whisker growth does not start immediately, but some time after the solder melts. The reason for the formation and growth of whiskers is the transferred-electron effect in a metal conductor, and the composition of the electrical resistance has no fundamental significance. The lack of oxygen in the electrolysis process is the basic condition for the formation of whiskers. Surface diffusion plays an important role in the formation of filamentary crystals. This research direction remains relevant at the present time. Today the country needs new structural materials that have valuable physicochemical properties. Microelectronics, medicine, defense issues, instrument-making industry, radiation safety, dosimetry, environmental protection - that's not all areas where grown filamentary crystals can be successfully used. Filamentary crystals have amazing properties, which in today's conditions deserve the close attention of our science. This, in turn, will help to more efficiently solve the issues of getting products that meet the requirements of environmental legislation, as well as human and environmental protection from anthropogenic factors.

Numerical analysis of the influence of surface-active substance in the melt on the distribution of modifying particles and crystallization at the treatment of metal surface by a laser pulse

A mathematical model is proposed for the process of modifying the metal surface layer by refractory nano-size particles with the aid of the pulse laser radiation, which accounts for the surface tension dependence on the presence of surface-active substance in the melt. Numerical modeling has been carried out, from the results of which the influence of the surface -active admixture on the character of forming flows, distribution of particles of the modifying substance in the metal, and the melt crystallization process have been estimated.

Adsorption of Gas-Phase Phenanthrene on Atmospheric Water and Ice Films

The adsorption of gas-phase phenanthrene on atmospheric water and ice films was investigated in a flow-tube reactor with a view to understanding the processing of semi-volatile organic compounds by fog and snow. Air-water (ice) interface partition constants were obtained by measuring the mass uptake of phenanthrene vapor on thin water and ice films with varying thickness. Adsorption enthalpies and entropies were obtained from the temperature dependence of the interfacial partition constants. The surface adsorption is the predominant mechanism for the uptake of phenanthrene in water and ice films with small film thickness or at low temperature. The adsorption of phenanthrene to ice resembles that to sub-cooled water and there's no significant difference between the adsorption of phenanthrene to water and that to quasi liquid layer (QLL) if we take into account the uncertainties on the thermodynamic quantities measured. Molecular dynamics simulations of phenanthrene at air/water and air/ice interfaces support these experimental observations. The interfacial air-water and air-ice partition constants of phenanthrene increased greatly in the presence of surface-active substances, indicating that surface active materials effectively enhanced the uptake of organic compounds by atmospheric water and ice films.

Solution Equilibria between Aluminum(III) Ion and some Fluoroquinolone Family Members. Spectroscopic and Potentiometric Study

Complex formation between aluminum(III) ion and fluoroquinolone antibacterials-either moxifloxacin (4th generation antibiotic) or fleroxacin (2nd generation antibiotic) were studied in aqueous solutions without and in the presence of sodium dodecylsulfate (SDS). The investigations were performed by glass electrode potentiometric (ionic medium: 0.1 mol/dm(3) LiCl, 298 K), UV spectrophotometric, multinuclear (1H and 13C) magnetic resonance and ESI-MS measurements. The experimental data were consistent with the formation of Al(HL)L2+, Al(HL)3+ AlL2+, Al(OH)L+ and Al(OH)2L complexes in the pH interval ca. 3-8 and up to 5 : 1 ligand to metal mole ratio with range of Al3+ concentrations between ca. 0.025 to 1.0 mmol/dm3. The binary complex, AlL2+ is fairly stable (log beta(1,0,1) ca. 11.0) and its stability increases in the presence of SDS. At higher concentration ratios of ligands to aluminum, up to 5 : 1, the complex Al(HL)L2+ is formed with rather high overall stability constant (log beta(1,1,2) ca. 24.0). The ESI-MS data generally, confirmed the derived model, and the formation of the complex with ligand to metal ratio 2 : 1. NMR measurements indicate that both ligands utilize 4-carbonyl and carboxyl oxygens as donor atoms. The presence of surface active substance, SDS, favors the formation of the complex in which the ligand is protonated, i.e. Al(HL) and its maximum formation is shifted toward milder acidic region (pH ca. 4). The aluminum-quinolone complexes may affect the bio-distribution of both, quinolone and/or aluminum ion upon concomitant ingestion of aluminum-based antacids or phosphate binders and fluoroquinolones.

Highly Stable Voltammetric Detection of Nitroaromatic Explosives in the Presence of Organic Surfactants at a Polyphenol‐Coated Carbon Electrode

AbstractA polyphenol‐coated screen‐printed carbon electrode is used for highly sensitive voltammetric measurements of the 2,4,6‐trinitrotoluene (TNT) explosive in the presence of surface‐active substances. The permselective/protective polyphenol coating offers excellent resistance to surfactant fouling, while allowing facile transport of the target TNT. High levels of gelatin, humic acid and sodium dodecyl sulfate (SDS) (up to 50 mg/L) have negligible effects upon the square‐wave voltammetric TNT response. The TNT peak current and potential remain nearly the same in the presence of these organic macromolecules, as compared to substantial peak suppressions and shifts at the bare electrode. Control of the electropolymerization time was used for achieving the desired exclusion of interfering surface‐active macromolecules while allowing transport of the target TNT. The response for ppm levels of TNT is highly linear and stable for prolonged operations in the presence of surface‐active substances. By meeting the high sensitivity, selectivity, stability, portability and low‐cost demands, such voltammetric sensing holds great promise for field‐based voltammetric monitoring of nitroaromatic explosive compounds.

Intermediate phase upon alloying Au–Ag nanoparticles under laser exposure of the mixture of individual colloids

The dynamics of Au–Ag alloy formation under laser irradiation of a mixture of the monometallic colloidal solutions are experimentally investigated and the factors influencing the alloy genesis are determined. Ag or Au nanoparticles are obtained by laser ablation of the corresponding metals in water or ethanol. Evidence is presented for the formation of an intermediate Au–Ag phase characterized by a transient red-shifted absorption peak. The changes in absorption spectrum and morphology of the colloidal particles are studied as a function of exposure time to laser radiation. It is found that the rate of alloying depends on both the concentration of nanoparticles and the presence of surface-active substances.

A Study on Operational Parameters for Advanced Use of Bismuth Film Electrode in Anodic Stripping Voltammetry

AbstractA study is presented on the characterization, evaluation and optimization of several key operational parameters for a reliable and effective use of a bismuth film electrode (BiFE) as an advanced replacement of the mercury film electrode in anodic stripping voltammetric measurements of trace heavy metals. Applying in situ preparation of the BiFE and employing lead(II) and cadmium(II) as model analyte ions, key parameters including bismuth precursor salt and substrate surface (platinum, gold, glassy carbon, carbon paste, carbon fiber) for bismuth plating, concentration as well as cationic and anionic composition of the measurement solution, solution pH and temperature, potential interferents, and stripping modes were carefully examined for their effects in the preconcentration and stripping steps. Parameters such as substrate surface (except platinum), precursor salt, solution matrix and temperature showed no or little impact on the BiFE performance in stripping analysis. On the other hand, the BiFE performance was found to be dependent on the solution pH (with maximum efficiency in the range of 4 to 5), on the stripping mode (with square‐wave voltammetry as the best choice) and to a certain degree on the presence of surface active substances. The results revealed that the non‐toxic solid‐state BiFE is applicable under a wide variety of conditions which proves it highly suitable for practical work in environmental trace heavy metal analysis.

Analytical Application of Silver Composite Electrode

Silver composite electrode prepared from silver and graphite powder and meth-acrylate resin presents a suitable sensor for the voltammetric measurements. Cathodic polarization of this electrode enables the determination of nitrates, nitrites, organic nitro compounds, and halide ions. The use of this electrode in differential pulse anodic stripping voltammetry enables the direct determination of lead in natural water samples without the elimination of the presence of surface-active substances or the dissolved oxygen. The effect of under potential deposition at the composite electrode differs from that effect produced by metallic silver electrode mainly at low concentrations of the deposited metal.

Water nucleation on aerosol particles containing surface-active agents

A theory of heterogeneous water nucleation on aerosol particles, which consist of soluble and surface-active substances has been developed. A similar approach has been used by Gorbunov and Hamilton (1996). The theory links interfacial free energiy of the surface of an embryo and chemical characteristics of aerosol particles with the ability of the aerosols to form water droplets under tropospheric conditions. The embryo formation free energy ΔG is a basis to calculate the water nucleation rate (Pruppacher and Klett, 1980) and probability of cloud droplet formation. An expression for ΔG was obtained as a function of a number of water molecules Nw in an embryo: Formula omitted (1) Here Rg is the universal gas constant. σeg is the interfacial free energy of the border between the surface of the embryo and gas phase. Sw is supersaturation of water vapour above a flat surface of pure water. Seg is the values of the surface area of the embryo that contains Nw moles of water. aw is the water activity in a solution of the same composition as the embryo (Pruppacher and Klett, 1980). Water nucleation rate and free energies in the case of aerosol particles that contain NaCl and NaOOCC15H31 have been calculated. It was shown that water nucleation on such aerosols is strongly influenced by the surface-active agent, see Figure 1. The presence of a small amount of the surface-active agent (the mass fraction of the surface-active agent in dry particles is about 10−2) considerably reduces the free energy of embryo formation. Calculation of the influence of the surfactant on the nucleation rate has shown a substantial increase in ability of an aerosol particle of cloud droplet production. An aerosol particle that contains a surface active substance needs less NaCl to become a cloud droplet. The presence of about 3% of the surfactant leads to a decrease in mass of NaCl particles by a factor of 4. Thus, atmospheric aerosol particles with surface active substances will produce more cloud droplets than particles without surfactants. Surface active substances that contain both hydrophobic and large hydrophilic groups exist in sea water and can be formed in the result of biomass decay. They can accompany sea salt fraction in atmospheric aerosols. Another source of substances that contain both hydrophobic and large hydrophilic groups is combustion, for example traffic emission or biomass burning. Thus, it is likely to expect the presence of surface active substances in the atmospheric aerosol. Figure omitted

Effect of surface-active substances on the rate of production of copper powder from copper sulphate solutions by cementation on zinc rods in gas sparged reactors

The effect of surface-active substances on the rate of diffusion-controlled cementation of copper on a single vertical zinc rod from dilute copper sulphate solutions was studied. Variables investigated were: nitrogen superficial velocity, concentration and type of surface-active substance. These variables were studied for their effect on the mass transfer coefficient of copper cementation. The mass transfer coefficient was found to increase with increasing superficial gas velocity. Increasing surfactant concentration was found to decrease the mass transfer coefficient. It was found that surfactants decrease the mass transfer coefficient by an amount ranging from 14% to 39% depending on the superficial gas velocity and type of surfactant added. The ability of the four types of surfactants to decrease the mass transfer coefficient increases in the order: CTMAB < Aspecon-1030 < SABS < NPPGE. Mass transfer data were correlated by the equation: Sh = 7.25 We 0.88 Sc 0.33 for the conditions: Sc = 1430 and 4.2 < We < 43.6, where Sh is a Sherwood number, We is a Weber number and Sc is a Schmidt number. In parallel with measuring the mass transfer coefficient, gas hold-up and solution surface tension were also measured to assess how these parameters are affected by the presence of surface-active substances.