Influence Of Surface-active Substances Research Articles

Influence of Surface-Active Substances and Substrates on the Wettability of Individual Aerosol Particles during Condensation by Environmental Scanning Electron Microscopy

The formation of liquid cloud droplets from aerosol particles in the Earth atmosphere is still under debate particularly because of the difficulties to quantify the importance of bulk and surface effects in these processes. Recently, single-particle techniques have been developed to access experimental key parameters at the scale of individual particles. Environmental scanning electron microscopy (ESEM) has the advantage to provide in situ monitoring of the water uptake of individual microscopic particles deposited on solid substrates. In this work, ESEM was used to compare droplet growth on pure ammonium sulfate (NH4)2SO4 and mixed sodium dodecyl sulfate/ammonium sulfate (SDS/(NH4)2SO4) particles and to explore the role of experimental parameters, such as the hydrophobic-hydrophilic character of the substrate, on this growth. With hydrophilic substrates, the growth on pure salt particles was strongly anisotropic, but this anisotropy was suppressed by the presence of SDS. With hydrophobic substrates, it is the wetting behavior of the liquid droplet that is impacted by the presence of SDS. The wetting behavior of the pure (NH4)2SO4 solution on a hydrophobic surface shows a step-by-step mechanism that can be attributed to successive pinning-depinning phenomena at the triple-phase line frontier. Unlike the pure (NH4)2SO4 solution, the mixed SDS/(NH4)2SO4 solution did not show such a mechanism. Therefore, the hydrophobic-hydrophilic character of the substrate plays an important role in the stability and dynamics of the liquid droplets' nucleation by water vapor condensation. In particular, hydrophilic substrates are not suited for the investigation of the hygroscopic properties (deliquescence relative humidity (DRH) and hygroscopic growth factor (GF)) of particles. Using hydrophobic substrates, data show that the DRH of (NH4)2SO4 particles is measured within 3% accuracy on the RH and their GF could indicate a size-dependent effect in the micrometer range. The presence of SDS does not seem to modify the DRH and GF of (NH4)2SO4 particles. This study shows that the water uptake on deposited particles is a complex process but, once carefully taken into account, ESEM is a suitable technique to study them.

Causes and treatments of foaming and overflow of calcium-based wet desulphurization slurry

During the operation of the calcium-based wet desulfurization system, slurry foaming and overflow are prone to occur, which is not conducive to the safe and stable operation of the desulfurization system. In order to solve the problem of slurry foaming, the main properties of the slurry were tested by taking the wet flue gas desulfurization device of a sintering machine of a steel company as an example. The foaming ability of the liquid is characterized by its foaming height and defoaming time, and the influence of surface active substances, particles and metal ions in the slurry on its foaming ability has been studied through multiple experiments. Combining the foaming mechanism and the desulfurization process, the cause of the slurry foaming is analyzed, and measures are given to prevent and treat the slurry foaming overflow to ensure the normal operation of the absorption tower.

The influence of surface-active substances on biofilm formation by the Acinetobacter calcoaceticus VKPM B-10353 strain

The influence of surface-active substances on biofilm formation by the Acinetobacter calcoaceticus VKPM B-10353 strain

Influence of surface-active substances on sulfur state during the autoclave leaching of zinc concentrates

Influence of surface-active substances on sulfur state during the autoclave leaching of zinc concentrates

Influence of surface active substances on the intensification of extraction when changing hydrodynamic indices of the technology of organopreparations

An influence of surface-active substances (SAS) on the change of physical characteristics of extractants of the group of organic preparations (chonsorid, heparin, and ronidase) was studied. Authors established rational concentrations of SAS in extractants, at which the minimum of coefficient of surface tension and the decrease in coefficient of dynamic viscosity are reached. For the solution of extractant of chonsurid – SAS butanol in the concentration of 0,05–0,06 % by weight, of heparin – butanol in the concentration of 0,5–0,6 % by weight, of ronidase – butanol in the concentration of 0,45–0,6 % by weight. Mean values of a near–surface laminar layer were established with the help of theoretical calculations, namely: for heparin – 1 mm, for chonsurid – 3 mm, for ronidase – 1 mm. Kinetics of extracting demonstrated an increase in the amount of the mass of extract when using extractants with SAS: for chonsurid – by 1,4 times, for heparin – by 1,7 times, for ronidase – by 1,9 times. Mathematical calculations proved a change in the similarity numbers under the influence of the surfactants, the Archimedean, Euler and Reynolds numbers were calculated and their values were compared. The Archimedean number changes its value for the extractants of chonsurid from 1028 to 10028, for those of heparin – from 3463 to 5910, for those of ronidase – from 990 to 6236. The value of the Reynolds number changes with the use of industrial extractants and the proposed extractants with the addition of SAS for chonsurid – from 18,6 to 91,6, for heparin – from 34,8 to 265, for ronidase – from 17,5 to 65,1. The Euler number with the use of industrial extractants for chonsurid is 170, for heparin – 92,2, for ronidase – 69,9, and when using the proposed extractants with the addition of SAS, it is: 37,5; 11,3; 12, respectively. Authors assessed hydrodynamic situation on the border of the contact “solid body – liquid” using the ratio of forces of surface tension to inertial forces on the basis of dimensionless set – surface number. Surface number changes its value when using industrial extractants and the proposed extractants with the addition of SAS for chonsurid from 2295 to 2164, for heparin from 530 to 346, for ronidase from 4641 to 197. The expediency of applying surface number was proved.

Влияние поверхностно-активных веществ на анодную поляризацию в процессе электролитического рафинирования меди

Влияние поверхностно-активных веществ на анодную поляризацию в процессе электролитического рафинирования меди

Influence of non-ionic and ionic surfactants on kinetics of the bubble attachment to hydrophilic and hydrophobic solids

Abstract The paper is devoted to kinetics and mechanism of the three-phase contact (TPC) formation by the colliding bubble at model hydrophobic (polytetrafluoroethylene – Teflon) and hydrophilic (muscovite mica) solid surfaces. To determine influence of type of the surfactant polar group the experiments were carried out in solutions of non-ionic (n-hexanol and n-octanol), cationic (n-octyl-(OTABr), n-dodecyl-(DDTABr) and n-hexadecyl-trimethylammonium (CTABr) bromides, and anionic (sodium hexadecyl sulfate (SHS)) surface active substances (SAS). The time of the TPC formation (tTPC) and timescale of rupture of the thin liquid film separating the colliding bubble and a solid surface was determined using high-speed video registrations. The tTPC was defined as the time span from the moment of the bubble first collision up to the liquid film rupture and formation of the TPC (dewetted) hole. It was shown that the influence of SAS on the kinetics of the TPC formation could be completely different depending on the hydrophilic/hydrophobic properties of the solid surface. At the Teflon surface the TPC was formed always, both in distilled water and in SAS solutions of various composition and concentration. Moreover, the tTPC was significantly prolonged at higher SAS concentrations, independently on the SAS type (ionic, non-ionic). At the mica surface the wetting film was stable and the TPC was never registered in distilled water as well as in solutions of non-ionic and anionic surfactants. However, the TPC was formed at the mica surface in solutions of cationic surfactants, but the tTPC values were decreasing with increasing cationic surfactants concentration. Mechanism of the TPC formation is presented and reasons of the completely different influence of SAS on kinetics of the TPC formation at the hydrophilic and hydrophobic solid surfaces are explained.

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.

The influence of surface-active substances on the crystallization process and magnetic properties of goethite nanoparticles

To prevent the process of aggregation and growth of α-FeOOH nanoparticles, during chemical syntheses various surface-active substances (SASs) with a concentration of 3 g/dm3 were added into the solution. The applied SASs were: cetylpyridinium chloride (CPC), sodium dodecyl sulphate (SDS), and complexone EDTA. Using various methods it was found that SAS molecules have a dual effect on the obtained nanoparticles: on one hand SAS application increases the number of small α-FeOOH nanoparticles with sizes of 2–5nm. On the other hand, SAS molecules react with surface atoms of the nanoparticles and form additional compounds.

Influence of Surface Active Substances on Magnetic Properties of Goethite Nanoparticles

To receive monosized goethite (α-FeOOH) nanoparticles powders in the process of chemical precipitation of iron salt and alkali various surface active substances (SAS) with concentration of 0.3% were added to water: C12H25NaO4S (anion active), C12H38ClN (cation active) and EDTA – C10H14O8N2Na2 (complexon). It has been determined that the magnetic properties of the nanoparticles under investigation change in comparison with the nanoparticles obtained without SAS addition. In all the samples under study very interesting saturation magnetization temperature dependences have been obtained. They indicate the difference in goethite temperature phase transformations connected with various surface layers formed on the nanoparticles under SAS influence.

Gas−Liquid Interfacial Area in the Presence of Different Chain Length Surfactants

The influence of surface active substances on the gas−liquid interfacial area in bubble contactors has been confirmed in previous works. The aim of the present study is analyzing the effect of the surfactant characteristics (in relation to the chain length of the hydrophobic zone) on the gas−liquid interfacial area using a bubble column as a contactor, as well as the behavior of different, commonly employed methods for the gas−liquid interfacial area determination. Two different methods for the gas−liquid area determination have been employed, and important differences between the values calculated by each method have been found. The discrepancies were assigned to different phenomena existing in this kind of systems, caused by the presence of surfactants at the gas−liquid interface. The experimental results obtained in this work under different operational conditions confirm that the chemical method contributes to higher values of interfacial area than the photographic method at low values of surfactant concentration, due to the important effect of this kind of substances on mass transfer. The effect of chain length also shows that a higher number of carbon atoms enhances the negative effect that surfactants produce upon the mass transfer.

Influence of Surface-Active Substance on Angular Properties of Spectra of Signals in Centimeter- and Millimeter-Wave Bands Backscattered by Water Surface

The influence exerted by the film of surface-active nonsolute substance upon azimuthal properties of several parameters of Doppler spectra of signals in centimeter- and millimeter-wave bands backscattered by the disturbed water surface in natural conditions is experimentally estimated. Possibility of using these effects for detection of surface-active substances is considered.

Influence of surface active substances on AKD sizing

Influence of surface active substances on AKD sizing

Thermocapillary convection around gas bubbles: an important natural effect for the enhancement of heat transfer in liquids under microgravity.

In the presence of a temperature gradient at a liquid-gas or liquid-liquid interface, thermocapillary or Marangoni convection develops. This convection is a special type of natural convection that was not paid much attention in heat transfer for a long time, although it is strong enough to drive liquids against the direction of buoyancy on Earth. In a microgravity environment, however, it is the remaining mode of natural convection and supports heat and mass transfer. During boiling in microgravity it was observed at subcooled liquid conditions. Therefore, the question arises about its contribution to heat transfer without phase change. Thermocapillary convection was quantitatively studied at single gas bubbles in various liquids, both experimentally and numerically. A two-dimensional mathematical model described in this article was developed. The coupled mechanism of heat transfer and fluid flow in pure liquids around a single gas bubble was simulated with a control-volume FE-method. The simulation was accompanied and compared with experiments on Earth. The numerical results are in good accordance with the experiments performed on Earth at various Marangoni numbers using various alcohols of varying chain length and Prandtl numbers. As well as calculations on Earth, the numerical method also allows simulations at stationary spherical gas bubbles in a microgravity environment. The results demonstrate that thermocapillary convection is a natural heat transfer mechanism that can partially replace the buoyancy in a microgravity environment, if extreme precautions are taken concerning the purity of the liquids, because impurities accumulate predominantly at the interface. Under Earth conditions, an enhancement of the heat transfer in a liquid volume is even found in the case where thermocapillary flow is counteracted by buoyancy. In particular, the obstructing influence of surface active substances could be observed during the experiments on Earth in water and also in some cases with alcohols.

Investigation of dissolution kinetics of thin Ge-Sb-S chalcogenide films

The kinetics and the mechanism of dissolution of fresh and illuminated chalcogenide layers from the Ge-Sb-S system have been investigated by the turn-table method. The relative roles of surface chemical reaction and diffusion in the heterogeneous dissolution process vs the layer composition have been established. Addition of a surface active substance (SAS) with cation-active organic nitrogen group to the alkaline solvent changes the dissolution kinetics. The selective influence of SAS at the topological phase transition of the structure allows to control the process of dissolution of the chalcogenide films.

Effects of surface-active substances in square-wave voltammetry and potentiometric stripping analysis of amalgam-forming metal ions

The influence of surface active substances (SAS) (Triton X-100, sodium dodecyl sulfate and dodecyl pyridinium chloride (DPC)) on the potentiometric stripping analysis (PSA), square-wave voltammetry (SWV) and anodic stripping square-wave voltammetry (ASSWV) of Cd2+, Cu2+, Zn2+ and Bi(III) are measured for various contact times and detergent concentrations. Diagnostic criteria for the presence of SAS in electrolytes are reported. Zinc ions accumulate in the adsorbed layer of DPC, probably as a ZnCl+ complex. An anomalous dependence of zinc SWV peak currents on the delay time is observed.

Influence of surface-active substances on the redox processes of metal ions: a contribution to the speciation analysis of metals in aquatic systems

The cathodic (reduction) and anodic (oxidation) waves of different heavy metal ions (Cu, Cd, In, Pb, Tl) were investigated in the presence of the non-ionic surfactant Triton X-100 and humic acid (HA) by electrochemical methods (differential-pulse voltammetry and a.c. voltammetry). The adsorption and complexation properties of the organic substances were also examined. Conclusions about the possible influences of organic matter on the speciation analysis of heavy metal ions in the bulk solution and on the mercury / water interface are drawn. For Cu the predominant reaction with HA will be complexation even at lower pH (1.6). In neutral and alkaline solutions Cd and Pb ions will be complexed either in the bulk of solution or at the electrode surface. At lower pH inhibition of oxidoreduction processes occurred owing to surface coverage of the electrode. Indium will be complexed with HA present at higher pH (3.84), whereas at lower pH the hydrophobic/hydrophilic effects play an important role in the interfacial region. Owing to the low tendency to form complexes and the small size of thallium ion, its oxidoreduction processes are not influenced by the presence of either Triton X-100 or HA.

Sorption Behavior of Carrier-Free Technetium-99mon Zinc Dust

Abstract The sorption behavior of 99mTc on zinc dust was studied as a function of pH. Optimum conditions have been found for the preconcentration of traces of Tc by zinc. The influence of surface-active substances and of complexing agents on the sorption of trace amounts of Tc on zinc dust has been also studied.

An experimental investigation of polymolecular solvate (adsorbed) films as applied to the development of a mathematical theory of the stability of colloids

After a critical discussion of the current concepts of solvation of surfaces and colloid particles, as well as of the methods of studying solvation, a new quantitative definition of solvation is advanced. This definition connects solvation with the disjoining action of thin layers of liquids, discovered and studied in earlier experiments described in the preceding papers of this series.The present paper describes a new, more convenient method of measuring both the thickness and disjoining action of thin layers for cases when they separate gas bubbles from solids (wetting films).Observations of non-equilibrium states of such wetting films are described.Experimental data are quoted, which are used in establishing an equation of state of a solvate layer. This equation expresses the equilibrium pressure (disjoining action) of a solvate layer for aqueous and non-aqueous media as a function of the thickness of the layer.The effect of electrolytes on the thickness of aqueous solvate films. as well as the influence of surface-active substances upon vaseline-oil films on steel surfaces, has been investigated.A theory of interaction of micelles, taking into account the disjoining action of thin layers of dispersion medium between the micelle surfaces, is advanced.In conclusion, the computations used in the latter theory are employed to elaborate a theory of slow coagulation and stability of colloids and disperse systems.

Influence of surface active substances on the electric surface properties of purple membrane fragments

The effect of ionic surface active substances: negatively charged sodium dodecyl sulphate (SDS) and positively charged cetylpyridinium chloride (CPC) on the electric properties of purple membrane fragments was studied electro-optically. The membrane charge asymmetry (permanent dipole moment, obtained from the low frequency part of the frequency dependence of the electro-optical effect and from the reversing pulse experiments, decreases upon increasing the co- or counter-ion concentration. The effect of SDS could be related to its specific interaction, predominantly with the extracellular membrane side, whereas CPC compensates the charge of the intracellular side. The results demonstrate the relation between the membrane charge asymmetry (obtained electro-optically) with the structure of the electric double layer, i.e., its interfacial nature.