Static Surface Tension Research Articles

Synthesis of Polyether Block Copolymers from 1,2-Epoxybutane and AEOn and Comparative Study of Physicochemical and Application Properties before and after the Synthesis.

In this study, the AEOnBO2 series of block polyoxybutenol ethers was synthesized by combining the AEO series of polyoxyethylene and preparing 1,2-epoxybutane (BO) block polyether using a semicontinuous method. The synthesis was performed by HPLC, MALDI-TOF-MS, FT-IR, and 1H NMR for structural analysis. The interaction parameters and surface tension of the systems before and after synthesis were studied using surface tension meter. The diffusion process of the systems before and after synthesis was studied using a KRÜSS bubble pressure tensiometer. The surfactant properties of AEOn and AEOnBO2 were evaluated by static and dynamic surface tension measurements. Each system formed a saturated adsorption layer in a water solution. The critical micelle concentration decreased dramatically after the introduction of BO groups, and the diffusion-adsorption process was consistent with the kinetic mechanism of hybrid diffusion. The microscopic self-assembled aggregate micellar behavior of all the systems was investigated using DLS, TEM, and SEM. The micellization process in all systems was spontaneous and enthalpy-driven, forming spherical aggregates, with the BO block reducing the aggregate diameter of the feedstock from 220.06 nm to about one-third of 80.02 nm. In addition, the dynamic contact angle, application, and physicochemical properties such as foaming and foam stabilization of each system were investigated. The contact angle was reduced from 70 to 50° at 120 s of stabilization, with a foam volume of 80 mL in all systems at 200 s. However, the AEOnBO2 showed accelerated foam decay at 500 s, with an increase in the contact angle from 70 to 50° at 200 s, but the AEOnBO2 showed accelerated foam decay at 500 s, with a decrease in the contact angle from 70 to 50° at 120 s stabilization. At 200 s, the foam volume of all systems was 80 mL, but AEOnBO2 showed an accelerated foam decay process, which shows that the BO group can accelerate the foam decay, and the comparative results show that the BO group can also optimize other application properties and physicochemical properties.

Interface properties and applications in laundry of the BS12-SAS mixed systems

In the BS12/SAS mixed systems, the solution exhibits acidity. BS12 can act as a cationic surfactant to form anionic-cationic complexes with SAS. In this study, the surface properties and application characteristics of the BS12/SAS mixed systems were investigated. The static surface tension, dynamic surface tension, and contact angle of BS12, SAS, and their different mixed molar ratios were measured at 25 °C to evaluate interaction parameters, activity coefficient, molar fraction, and thermodynamic variables of surfactants in the mixed micelles. The results demonstrated that the BS12/SAS mixed systems deviated from the ideal state due to the strong molecular attraction between the two components, resulting in a synergistic effect. The mixed systems exhibited higher surface activity and lower critical micelle concentration. Thermodynamic analysis indicated that the spontaneous micellization of binary mixtures of BS12 and SAS occurred through both enthalpy-driven and entropy-driven processes. The adsorption kinetics data revealed that the mixed systems followed a diffusion-adsorption process. Contact angle measurements demonstrated that BS12/SAS possesses superior ability to reduce surface tension, which facilitated rapid droplet diffusion and efficient wetting of the matrix within a short time period. Furthermore, the aggregation behavior of individual surfactants and the two composite systems in aqueous solutions was analyzed using DLS and TEM to investigate their effects on the wetting, emulsification stability, foaming stability, and decontamination capability of liquid paraffin.

Surfactant system of the lungs in antiphospholipid syndrome under the conditions of administration of the immunosuppressive agent FTY-720

Antiphospholipid syndrome (APS) is a thrombophilic disease in the pathogenesis of which the leading role belongs to antibodies reacting with antigenic determinants of phospholipids. APS is a systemic autoimmune pathology that involves many organs and systems in the pathological process, including the respiratory system. Given the fact that the lung surfactant is mainly represented by phospholipids, it can be presented that the surfactant is damaged and its functioning is impaired in APS. The results of our experiments showed that in antiphospholipid syndrome, there was a decline in the functional activity of the surfactant and a change in its biochemical composition. The introduction of FTY-720 normalized the parameters of the lung surfactant system, which were changed during the modeling of antiphospholipid syndrome. The work shows the effectiveness of the therapy of this autoimmune pathology with immunosuppressor FTY-720, which is a structural analogue of endogenous sphingosine. The effect of the drug is based on the modulation of sphingosine-1 phosphate receptors of lymphocytes. The main effect of the immunosuppressor FTY-720 as a result of receptor interaction is a decrease in the number of circulating lymphocytes. The research involved 85 white random bred male rats: Group 1 (APS modeling) consisted of 30 rats who were intravenously injected with cardiolipin antigen at a total dose of 0.2-0.4 mg per rat every other day for three weeks; Group 2 (control) consisted of 25 rats who were injected with 0.9% NaCl solution according to the same scheme; and Group 3 including 30 rats in which APS was combined with the administration of the immunosuppressive agent FTY-720 (intraperitoneally 1 mg/kg of animal weight). Three weeks later, there was an operation conducted with the purpose of extraction of the bronchopulmonary complex. After extraction of the bronchopulmonary complex, its triple lavage was carried out with 0.9% NaCl solution. The material of the experimental study was a lavage liquid, in which the biophysical and biochemical parameters of the surfactant were studied. Langmuir–Blodgett method was used to identify static, minimal and maximal surface tension. These figures were used to identify integrative indicator reflecting surfactant characteristics – the Clements stability index. The fractional composition of surfactant phospholipids was determined by thin-layer chromatography. The results of our experiments showed that in antiphospholipid syndrome, there was a decline in the functional activity of the surfactant and a change in its biochemical composition. The introduction of FTY-720 normalized the parameters of the lung surfactant system, which were changed during the modeling of antiphospholipid syndrome.

Flowback Additive for Acidizing Fluid to Stimulate Carbonate Gas Reservoirs

Summary Acidizing of oil- and gas-bearing carbonate reservoirs is generally undertaken by using strong mineral acids such as hydrochloric acid (HCl) to enhance permeability. One of the major challenges associated with HCl injection is tuning the reactivity profile to favor the transport of live acid deep into the reservoir while achieving a minimum rock face dissolution. The mineral acid is therefore emulsified in a hydrocarbon phase (e.g., diesel) to retard its reactivity with the rock matrix. The use of emulsified acid is hindered by several limitations such as low emulsion stability at high temperatures, pumping limitations due to high viscosity, the potential of formation damage, and cumbersome mixing procedures at the field scale. In addition, the brines formed as a result of this reaction can be difficult to produce due to higher density and capillary pressures, unfavorable wettability, and low formation pressure. Here, we report on the development of dual-purpose additives that were specifically designed to enhance the recovery of high-density brines and retard the acid/rock reactivity upon addition to the stimulation treatment. Accordingly, seven new additives with fluid flowback properties were developed for use in a single-phase acidizing fluid consisting of HCl (15 wt% and 28 wt%) with the required additives, such as corrosion inhibitor and intensifier, and H2S scavenger. The flowback enhancers (FBEs) were formulated from a blend of water, ester or terpene solvents, alcohols, and surfactants to form optically clear nano- and microemulsions. Surfactant selection was driven by the need to exhibit demulsification properties with condensate, high chemical and thermal stability, compatibility in strongly acidic media, and high-density brines under harsh reservoir conditions. To assess the FBE performance in acidizing formulations (i.e., to serve as both an FBE and retarder), screening studies consisting of static rock dissolution tests and surface tension measurements were performed to downselect FBEs suitable for this application. This was coupled with brine displacement tests in addition to compatibility and stability studies. FBEs that demonstrated superior performance were then selected for further evaluation under reservoir conditions [i.e., core flow matrix acidizing to measure regained permeability and computed tomography (CT) scan for analyzing the wormhole propagation]. The droplet size of the as-prepared nano- and microemulsions was found to be between 10 nm and 850 nm. The FBEs formulated in this study were found to prevent emulsion formation in the presence of condensate and demonstrated remarkable chemical and thermal stability in concentrated acid at temperatures up to 300°F for a duration of up to 24 hours, as confirmed by the consistent low surface tension values (21–29 mN/m). With regard to fluid displacement, column tests performed under ambient conditions revealed quick brine displacement with recovery exceeding 75 vol% in comparison with 16 vol% in the absence of the FBE. Interestingly, the addition of a select FBE from this study to 28 wt% HCl was found to retard the reaction of carbonate dissolution at room temperature. This led us to assess the performance under reservoir conditions utilizing core flow testing. Accordingly, the addition of FBE-F to 28 wt% HCl led to an improvement in permeability by up to 267% as compared with 15% without FBE added. These results are further supported by the CT scan images of the acidized cores, which revealed the formation of a deeper wormhole in the presence of a select FBE.

Adsorption and Aggregation Behaviors of Oleyl Alcohol-Based Extended Surfactant and Its Mixtures.

An oleyl alcohol-based extended surfactant, sodium oleyl polyethylene oxide-polypropylene oxide sulfate (OE3P3S), was synthesized and identified using FT-IR and 1H NMR. The adsorption and aggregation behaviors of OE3P3S and its mixture with cationic surfactant alkyltrimethylammoniumbromide (ATAB) were investigated under different molar ratios. The static surface tension analysis indicated that the critical micellization concentration (cmc) and the critical surface tension (γcmc) of OE3P3S were 0.72 mmol/L, and 36.16 mN/m, respectively. The cmc and γcmc values of the binary system were much lower than that of the individual component. And the cmc values of OE3P3S/ATAB = 6:4 mixtures decreased with an increase in the chain length of the cationic surfactant in the binary system. It was found from the dynamic surface tension that there was a slower diffusion rate in the binary system compared to the pure surfactant, and the adsorption processes for OE3P3S/ATAB = 6:4 were mixed diffusion-kinetic adsorption mechanisms. With a combination of DLS data and TEM measurements, formations of vesicles in OE3P3S/ATAB = 6:4 solutions appeared to occur at a concentration of 0.05 mmol/L. By studying the formation of liquid crystal structures in an emulsion prepared with OE3P3S as the surfactant, it was found that the oil-in-water emulsion is birefringent with a Maltese cross texture, and the rheological properties revealed its predominant viscoelastic behavior and shear thinning properties.

Synergistic effects of nonionic surfactants ethoxylated alkylamines and sodium dodecyl sulfate in mixed systems

HypothesisIn general, the performance of surfactant hybrid systems is better than that of single surfactants, so surfactant hybrid systems are widely used in various industries. As a very important class of nonionic surfactants, ethoxylated alkylamines have been widely used in industries such as washing, coating, and pesticide, but little research has been conducted on their mixed systems. In order to improve the utilization efficiency of surfactants and reduce wastage, the surface properties and aggregation behavior of ethoxylated alkylamine mixed systems should be further explored. ExperimentIn this study, the nonionic surfactant ethoxylated dodecylamine (AC-1202) and the anionic surfactant sodium dodecyl sulfate (SDS) were used to form a mixed system. The static surface tension and interaction parameters of the mixed system under the influence of inorganic salt ions were investigated using a KRÜSS K12 surface tensiometer. The diffusion process of the mixed system was investigated using a KRÜSS bubble pressure tensiometer. At the same time, the aggregate behavior of the mixed system was studied by particle size analyzer. In addition, the contact angle and rheological properties of the mixed solution were also investigated. FindingsThe SDS/AC-1202 mixture system formed a synergistic effect that could reduce the CMC value to 24.20 mN/m and the CMC value was as low as 22.89 mN/m after the addition of inorganic salts. The mixed system conforms to the kinetic mechanism of mixing and diffusion and the Ostwald de model for non-Newtonian fluids. Finally, there is a good aggregation pattern in the mixed system, and the stronger synergistic effect will lead to the reduction of the average particle size of the mixture to 45.41 nm.

Effect of Different Ethylene Oxide Addition Numbers on the Performance of Polyoxyethylene Tallow Amine as a Pesticide Emulsifier.

Surfactant reduces the surface tension of liquids, resulting in improved emulsion stability, and there is great interest in pesticide additives. Ethoxylate is often used as a pesticide emulsifier. However, the degree of ethoxylation and the existence of dioxane byproducts can significantly affect the performance of emulsifiers. Here, a series of polyoxyethylene tallow amines with the addition of different numbers of ethylene oxide (EO) were synthesized and characterized. Their physical and chemical performances were measured. The ability of POEA as a surfactant to reduce water surface tension and the surface adsorption of molecules were assessed based on the static and dynamic surface tensions. The results show that the surfactant molecules preferentially form a saturated adsorption layer in solution, and the mixed-diffusion-kinetics mechanism dominates the adsorption process. With the increase of the EO addition number, the emulsifying property of POEA increases, while the wetting property gradually decreases and the contact angle increases. These results can provide a basis for the selection of pesticide additives. At the same time, the mechanism of removing dioxane by ethoxylate is described, and a simple and low-consumption method is put forward to reduce the dioxane content. It provides a new idea for the removal of dioxane.

Effect of adjuvants on physicochemical properties of lime sulfur on flower/paraffin and application on flower thinning.

Adjuvants can effectively enhance the utilization rate of pesticides, but the application of adjuvants in plant growth regulators is rarely studied. This work explored the effects of adjuvants dioctyl sulfosuccinate sodium salt (AOT) and methyl oleate (MO) on lime sulfur (LS), especially the drop behavior on flower and paraffin surface. The results showed that the addition of AOT and AOT+MO can significantly reduce the static and dynamic surface tension of LS from 72mN/m to 28mN/m and 32mN/m respectively, and increase the spreading factor from 0.18 to 1.83 and 3.10 respectively, reduce the bounce factor from 2.72 to 0.37 and 0.27 respectively. The fluorescence tracer test showed that the addition of adjuvants could promote the spreading and permeation of droplets. The field test results revealed that the flower thinning rate of adjuvant and non-adjuvant were 80.55% and 54.4% respectively, and the flower thinning effect of adding adjuvant was the same as that of artificial which the flower thinning rate was 84.77%. The quality of apples treated with adjuvants was similar to that treated with artificial, and the weight of single fruit increased by 24.08% compared with CK (spray water). The application of tank-mixture adjuvant could reduce the dosage of LS for thinning agent application, improve apple's quality, and decrease labor cost and improve the economic benefits of fruit planting and the environmental benefits of plant growth regulators.

Equilibrium and dynamic surface properties of cationic/anionic surfactant mixtures based on alcohol ether sulfate

The equilibrium and dynamic surface properties of anionic surfactant alcohol ether sulfate with different EO distribution(C-AE2S and N-AE2S) and cationic surfactant tetradecyltrimethylammonium bromide (TTAB) mixtures under different molar ratios were investigated. Their surface activities, adsorption, and spreading performances were investigated by static/dynamic surface tension measurements, molecular dynamics simulation, and dynamic contact angle techniques at 298 K. The static surface tension analysis reveals that the critical micellization concentration (cmc) values and the surface tension at cmc (γ cmc) of the binary systems are much lower than that of the individual component. Compared with C-AE2S/TTAB, N-AE2S/TTAB systems have higher cmc and lower γ cmc. It was found from the molecular dynamics simulation that negative charges of C-AE2S were drastically neutralized by the positively-charged TTAB at the interface in the system of C-AE2S/TTAB. The dynamic surface tension results indicate that the adsorption process of aqueous solutions for both C-AE2S/TTAB and N-AE2S/TTAB are mixed diffusion-kinetic adsorption mechanisms. From the dynamic contact angle measurements, it could be obtained that the mixtures exhibit better spreading behavior than that of the individual component and N-AE2S/TTAB systems have lower contact angles than that of C-AE2S/TTAB at the same mixing ratios.

Formation Damage Caused by Wax Deposition Results in Shale Production Decline

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210414, “First Evidence for Shale Production Decline as a Result of Formation Damage Caused by C60+ Paraffin Wax Deposition: A Permian Case Study,” by Amir Mahmoudkhani, SPE, Locus Fermentation Solutions, and Jonathan Rogers and Martin Shumway, SPE, Locus Bio-Energy Solutions, et al. The paper has not been peer reviewed. _ Analysis of production decline curves revealed that three candidate wells in West Texas depleted faster than indicated by a type decline curve, indicating a potentially abnormal permeability-reduction mechanism. A biosurfactant-based squeeze program was recommended and applied in three horizontal wells. The biosurfactant treatment offers an alternative and economical method for remediation of formation damage caused by high‑molecular‑weight paraffin wax deposition in porous media that does not require costly intervention techniques to apply. Introduction The Bone Springs horizontal oil play in the Delaware Basin spans from southeast New Mexico into West Texas. Stacked, multipay reservoirs, each with diverse rock properties, possess upside but also complexity. The initial targets in the play were conventional sandstones. Wells then tapped into carbonate lenses and, ultimately, low-permeability sandstones. As a result of horizontal drilling technology combined with hydraulic fracturing, very thin sands and other facies are now being produced. Generally, reservoir quality of this unconventional hydrocarbon system is controlled by carbonate content, where increased carbonate content typically is associated with lower productivity. Experimental Methods All crude oils exhibited precipitation of organics at ambient laboratory temperatures. Even after storing crudes at the bottomhole temperature of 140°F, a small amount of wax remained insoluble in bulk liquid. Samples of formation drill cuttings were received for various depth intervals between 8,500 and 12,000 ft. X‑ray diffraction analyses of solids revealed quartz as the major mineral phase, with clays and carbonates account for remaining phases. Combined fractions with 160-micron size were used for microcolumn oil-recovery screening tests. Carbon distributions of oils and waxes were performed by high-temperature gas chromatography (HTGC). The Du Noüy ring method was used to measure static surface tensions of biosurfactant solutions at different concentrations and was applied to calculate critical micelle concentrations at ambient temperature. Interfacial tension (IFT) measurements were performed using a drop-shaped tensiometer using the pendant-drop method. Finally, the IFTs of oil in synthetic formation water and in biosurfactant solutions prepared in city tap water were determined. Contact-angle measurements also were performed. The wax-appearance temperature (WAT) of crude and wax samples was determined by the differential scanning calorimetry method. Spontaneous imbibition experiments were performed using the Amott-cell method at reservoir temperature. Berea sandstone core plugs (25×50 mm) with a permeability of 385 md and porosity of 18.4% were used. Core plugs were saturated with homogenized crude oil samples at 140°F for 7 days.

On the rebound of soapy drops.

Pure water is known to bounce on super-hydrophobic materials, and we discuss here whether this remains true if the surface tension of water is lowered by either alcohol or surfactants. After determining the threshold in surface tension below which drops stick to the substrate, we show that a decrease of surface tension makes the rebound slower, a consequence of the reduced stiffness of this kind of spring. We also report that water with "slow" surfactants can still bounce despite a static surface tension smaller than the rebound threshold, which is interpreted as an effect of dynamic surface tension. The liquid is substantially deformed at impact, which impoverishes the surfactants at the its surface and thus can trigger repellency for a wetting liquid.

Bubble growth and detachment process in surfactant solutions: a study of 90% pure sodium dodecyl sulfate

We have investigated the effect of the surfactant Sodium Dodecyl Sulfate on the bubble growth and detachment processes in a bubble column system. A modified pendant drop model was employed to determine the dynamic surface tension. The dynamic surface tension approached the static surface tension value within a few seconds. A photographic technique and a laser-based electro-optical method were used to study the bubble size variation and the generation frequency, respectively. Parameters like bubble generation frequency, size, growth rate, and contact angle were found to be a strong function of surfactant concentration. Our results show that the addition of surfactant significantly reduces the bubble lifetime at the orifice. Such a decrease in the bubble lifetime has a direct impact on the bubble growth rate and departure size. Furthermore, bubble parameters vary with surfactant concentration only up to the critical micellar concentration.

Clinical relevance of pancreatic fistula in pancreas transplantation: a Comprehensive Complication Index (CCI)-based analysis of postoperative outcomes and predictors of graft survival

Guanidine hydrochloride and urea have different effects on the surface properties of lysozyme solutions due to different interaction mechanisms between the protein and denaturants: an increase in the guanidine hydrochloride concentration leads to noticeable changes in the dynamic surface elasticity, while the main effect of urea consists in a significant drop of the static surface tension.

Promoting the utilization efficiency of agrochemicals via short-chain nonionic fluorinated synergist: Strategies and working mechanisms

Wastage of agrochemicals results in considerable environmental pollution and economic loss. The use of trisiloxane surfactants as synergists has proven to allow for reduction in agrochemical application rates, but these surfactants show poor resistance to hydrolysis, which can attenuate their synergistic effects. Herein we report the development of a short-chain nonionic fluorinated surfactant, designated mPEG200-TEOH-6, as a novel agrochemical synergist. In contrast to conventional long-fluorocarbon chain surfactants, our short-chain fluorinated surfactant can avoid the risk of persistence and bioaccumulation in the environment. We determined the thermal storage stability of mPEG200-TEOH-6 and investigated its effects on the static surface tension, dynamic surface tension, contact angle, and thermal storage stability of four agrochemicals solutions, which explained its synergistic efficacy. In addition, we compared its effects with those of the commercial surfactant Silwet 408. Both mPEG200-TEOH-6 and Silwet 408 clearly improved the utilization efficiency of the agrochemicals, but mPEG200-TEOH-6 displayed substantially greater synergistic efficiency than Silwet 408; specifically, the former markedly decreased the static surface tension of agrochemical solutions, increased their diffusivity and wettability, and decreased their LC50 values. Strikingly, we found that mPEG200-TEOH-6 was more stable than Silwet 408 under thermal storage conditions. The result presented herein can be used to guide the use of surfactants and agrochemicals in agriculture.

Synthesis of phospholipid based zwitterionic surfactant from coconut oil source and characterization of their interfacial, antiseptic and antiviral properties

In this study, a phospholipid based zwitterionic surfactant CDP-W (cocamidopropyl propylene glycol (PG)-dimonium chloride phosphate) was synthesized from coconut oil source and the structure of the prepared surfactant CDP-W was identified by FT-IR, 1H NMR and 13C NMR analysis. Interfacial property measurements such as CMC, static and dynamic surface tensions, interfacial tension, foamability and foam stability have revealed that CDP-W surfactant possesses better surfactant activity and more effective in lowering surface free energy than CAPB (cocamidopropyl betaine) which is a zwitterionic surfactant widely used in cosmetics, personal products and household products. Environmental compatibility tests such as biodegradability, oral toxicity, skin irritation and eye irritation showed that CDP-W surfactant is easily biodegradable, non-toxic, mild and non-irritating to skin and eye. In particular, CDP-W reveals excellent antiseptic and antiviral properties without using any additional preservative and disinfectant, suggesting that CDP-W surfactant can replace CAPB in the formulation of cosmetics, personal products and household products.

A designed setup of low-priced in-house goniometer/tensiometer

In many educational institutes and industries, the contact angle and surface tension analysis are done to measure the quality of a solid surface and of a liquid. In order to determine these, the sessile and pendant droplet method are the most widely used metrics, which are conventionally obtained using commercial goniometer/tensiometer. In view of the growing concern regardingcompact and inexpensive but accurate experimental devices, we have developed a low-priced in-house goniometer/tensiometer. This device has the benefit of easiness, compactness, and movability over the conventional measurement instruments. In this study, we have used the commercial Drop image advanced as well as the Drop analysis plugin in ImageJ with high quality sharp edges images to compute static contact angle and surface tension values. Detailed procedure to measure them have been discussed in this work. To validate the apparatus, various water-based solutions have been considered. The surface tension values obtained using the apparatus are in good agreement with those reported in the literature. However, the apparatus needs to validate for highly wettable and volatile fluids. The efficacious manifestation of this device to determine the contact angle is a compelling improvement in the area as it disrupts the trendof a bench designated setup which is heavy, bulky and expensive and are not suitable for field work. The standard threaded syringe-based low-priced goniometer/tensiometer fabricated is affordable, being less than 40 USD or 3000 INR. Variety of water-based solutions like Millipore water, SDS solution at CMC * (8.1 mM), SDS solution at CMC/2, SDS solution at 2xCMC have been considered for validation and compared with surface tension values. Such a low-cost goniometer prototype can serve the technological needs of scientific research labs, in imparting practical learning about repeatability and highly beneficial for industrial applications.

Реологические свойства сыворотки крови при метаболическом синдроме у больных остеоартрозом

Интегральные реологические свойства сыворотки крови больных остеоартрозом зависят от наличия всех составляющих метаболического синдрома (в первую очередь от параметров инсулинемии, тяжести инсулинорезистентности, индекса массы тела, урикемии, липидемии, типа гиперлипидемии, характера артериальной гипертензии и периферического сосудистого сопротивления), а в патогенезе таких признаков, как остеофитоз, остеокистоз, остеоузурация, остеопороз, субхондральный склероз, поражение менисков, развитие кист Бейкера и энтезопатий, участвуют показатели адсорбционно-гликемического интегрального коэффициента, гликемического коэффициента межфазной активности, модуля вязкоэластичности, статического поверхностного натяжения и фазового угла тензиограмм.

Measurements of Static and Dynamic Bubble Surface Tension Using a Deformation-Based Microfluidic Tensiometer.

The surface tension of bubbles is critical for processes involving mixed liquid-gas systems, from sea spray aerosol generation to firefighting foam aspiration. In particular, the size- and surfactant-dependent time scales of dynamic surface tension decay due to adsorption of surface-active chemicals at the curved interface significantly dictate the multiphase system dynamics. While size-dependent surfactant adsorption and interfacial dynamics have been well characterized for liquid-liquid systems using microfluidic platforms, application of microfluidic methods to liquid-gas systems has received less attention. This work uses a high-throughput microfluidic tensiometer to measure the static and dynamic surface tension of microscale bubbles compared with millimeter bubbles characterized by pendant drop. It is shown that the static surface tension measurements for surfactant-free interfaces with microfluidics show good agreement with pendant drop for most systems. At the same time, its accuracy can be affected by bubble pressure, inertia force at high Re, drag force, bubble expansion, and image processing limitation. In the presence of surfactants, the dynamic surface tension measurements show that both smaller bubbles and higher surfactant concentrations can lead to a much shorter time to reach equilibrium compared with pendant drop, similar to the observation for liquid-liquid interfaces. This work shows the potential of a microfluidic tensiometer to capture early time surface tension decay and accurately measure surface tension even in the presence of Marangoni stress tangential to the interface.

Linking molecular structures of yeast-derived biosurfactants with their foaming, interfacial, and flotation properties

Yeast-derived bola amphiphiles have attracted growing attention in various industrial sectors as green reagents. However, their physico-chemical properties relevant to mineral separation by froth flotation are poorly explored. To bridge this gap, we studied the foaming, interfacial, and flotation properties of acidic sophorolipid (ASL), acidic glucolipid (GL) and alcoholic glucoside (GS) obtained from strain engineering of the yeast Candida bombicola by molecular editing of the headgroups. Bench-scale flotation testing of a copper sulfide ore showed that ASL can effectively separate copper sulfides (85% recovery at 20% grade), GL is less effective (ca. 60% recovery and 13% grade), while GS is a poor collector. To understand this trend, we studied the interfacial and foaming properties of these three biosurfactants. The surface tension study reveals that, contrary to GS, self-assembly of both ASL and GL at the air–water interface is pH-responsive, suggesting that both the biosurfactants acquire a Π-shape. The dependence of the foaming properties of all the three surfactants on pH and concentration does not correlate with the trends in the static surface tension, suggesting the critical roles of dynamic factors, interfacial elasticity and interfacial viscosity. Hydrophobicity of djurleite (a model copper sulphide) in the presence of the three surfactants was assessed using the contact angle and Hallimond flotation methods. ASL and GL only float the pure mineral at alkaline pH, which is consistent with the contact angle data. In contrast, even though GS does not have a significant effect on contact angle, it floats djurleite in a wide pH range, which is explained by the mechanical entrainment of hydrophilic mineral particles in rich GS foams. Overall, these results demonstrate the potential of carboxylic bola biosurfactants for the recovery of copper sulfides from ores. They also bring new insights into the interfacial and foaming properties of bola biosurfactants, which can assist their introduction into other industries.

Зв’язок реологічних властивостей сироватки крові зі станом вегетативної нервової системи при ревматоїдному артриті

Актуальність. Ревматоїдний артрит (РА) належить до найбільш частих запальних хвороб суглобів, і численність таких пацієнтів всюди збільшується, завдаючи величезного медико-соціального й економічного збитку. Важлива роль у патогенезі РА відводиться порушенням функції вегетативної нервової системи (ВНС), стан якої тісно пов’язаний із реологічними властивостями сироватки крові (РВСК). Мета дослідження: оцінити співвідношення «вегетативного паспорта» хворих на РА і вегетативної дисфункції з РВСК при різних варіантах перебігу хвороби. Матеріали та методи. Обстежено 173 хворих на РА у віці від 18 до 79 років (в середньому 46 років), серед яких було 21 % чоловіків та 79 % жінок. Тривалість маніфестації захворювання становила 10 років, серопозитивний за ревматоїдним фактором і антицитруліновими антитілами варіант РА встановлено в 3/4 випадків, позасуглобову (системну) форму хвороби діагностовано в 37 % спостережень. З використанням комп’ютерного тензіометру «PAT2-Sinterface» (Німеччина) визначали поверхневі показники сироватки крові — в’язкість, пружність, натяг, релаксацію й модуль в’язкоеластичності. Результати. «Вегетативний паспорт» визначав інтегральні клініко-лабораторні та інструментальні ознаки РА, при цьому тяжкість вегетативної дисфункції прямо корелювала з темпами прогресування патології суглобів, а у симпатотоніків — з початковими параметрами ревматоїдного фактора в крові й ступенем активності РА. Зміни РВСК супроводжувались збільшенням рівноважного (статичного) поверхневого натягу, що реєструвалося в 70 % випадків. Інтегральний стан міжфазної активності, релаксаційних та в’язкоеластичних характеристик крові визначав тип ВНС і наявність у хворих вегетативної дисфункції (ваготонікам властиві підвищення модуля в’язкоеластичності й зниження поверхневого натягу, симпатотонікам — підвищення поверхневого натягу та зниження поверхневої в’язкості). Параметри РВСК пов’язані з вираженістю вегетативних розладів, а показник поверхневої в’язкості має прогностичну значущість. Висновки. Розвиток вегетативної дисфункції пов’язаний не лише з особливостями перебігу суглобового синдрому і екстраартикулярних ознак РА, а й зі станом ВНС, що бере участь в порушеннях РВСК. У майбутньому буде корисною оцінка стану ВНС для подальших своєчасних реабілітаційних заходів щодо захворювання.