Increasing Surfactant Concentration Research Articles

Surfactant-Driven Dynamic Changes in Rheology of Activated Carbon Slurry Electrodes.

Carbon black slurry electrodes are an effective means to improve flow battery performance by increasing the active surface area necessary for electrochemical reactions with a cost-effective material. Current challenges with this specific flow battery chemistry include the stability and flowability of the carbon black suspensions, especially in response to formulation choices. Advancing the manufacturing, operation, and performance of these redox flow batteries requires a deeper understanding of how slurry formulation impacts its rheological profile and ultimately battery performance. In response to this need, the linear and nonlinear rheological responses of activated carbon (AC) based slurry electrode materials used in an all-iron flow battery in the presence of a nonionic surfactant (Triton X-100) were measured. Results from these measurements show the slurry is a colloidal gel with elasticity remaining constant despite increasing surfactant concentration until α (= Csurf/CAC) < 0.65. However, at α ≥ 0.65, the slurry abruptly transitions to a fluid with no measurable yield stress. This critical surfactant concentration at which the rheological profile undergoes a dynamic change matches the concentration found previously for gel collapse of this system. Moreover, this transition is accompanied by a complete loss of electrical conductivity. From these data we conclude the site specific adsorption of surfactant molecules often used in slurry formulation has a significant and dramatic impact on the stability and flowability of these suspensions. Work presented herein demonstrates the importance of additive choices when formulating a slurry electrode.

Quercetin Solid Lipid Microparticle Stability and Deposition in Rat Lungs: A Study of Surfactant Effect

This study aims to determine the effect of surfactant concentration on Quercetin SLM as a potential carrier of respiratory diseases, especially ones resulting from oxidative stress injury. Quercetin is a natural antioxidant with high activity. SLM was formed with 5% compritol 888 ATO as a lipid and different concentrations of poloxamer 188 as a surfactant. SLM was produced by a combination of emulsification and sonication involving freeze drying. SLM is characterized by organolepsis, morphology, yield, particle size, drug loading, and entrapment efficiency. The antioxidant activity of quercetin SLMs was tested using the ABTS method. SLMs are characterized as having round and smooth morphology, high yield (F1 88.53%; F2 91.44%; F3 92.87%); particle size (F1 1.81 um; F2 1.90 um; F3 1.94 um); high drug loading (F1 15.96%; F2 13.74%; F3 13.19%); and high entrapment efficiency (F1 96.53%; F2 87.94%; F3 87.48%). Increasing surfactant concentration did not produce a significant difference between formulas. Quercetin SLM showed high antioxidant activity (Quercetin 94.43%; F1 94.35%; F2 94.36%; F3 94.37%). SLM was stable at storage temperatures between 25°C and 40°C. The effect of surfactant can be seen on particle size, drug loading, and entrapment efficiency at 40°C. Results of in vivo deposition study indicated that all SLM formulas were able to deliver quercetin to the lungs. Increasing the concentration of surfactant in Quercetin SLMs made no difference to the lung deposition as confirmed by observations conducted at 1 hour and 4 hours. Quercetin SLM has the potential for lung delivery by inhalation.

Multilevel Categoric-One Factor Optimization Of Cremophor Rh 40 As Surfactant in Cream With Calabash (Crescentia cujete Linn) Leaves Ethanolic Extract

Indonesia's location on the equator is exposed to a high UV index, which triggers various health problems due to ultraviolet radiation, including melanoma. Melanoma is the 5th deadliest cancer that develops from the malignant transformation of melanin in oxidative stress conditions. Therefore, antioxidants are needed. Calabash is a natural exogenous antioxidant with an IC₅₀ value of 80.21 µg/mL (strong activity). Optimal formulations of cream containing calabash are determined by the concentration of ingredients and the selection of comprehensive analytical methods. This research aims to optimize cream preparations of calabash leaves ethanol extract with varying concentrations of Cremophor RH 40 as a surfactant using the multilevel categoric-one factor method. The cream was made with Cremophor RH 40 concentrations of 5%, 10%, and 15%. The cream was made by mixing the water phase (Nipagin, Glycerine, and Aquadest) and the oil phase (Cremophor RH 40, BHT, IPM, Cetostearyl alcohol, and Nipasol) after both phases reached a temperature of 60ºC in mixer speed no 1 for 15 minutes then followed by adding calabash leaves ethanolic extract until a homogeneous cream was formed. The parameters observed were organoleptic, homogeneity, the type of cream, pH, viscosity, dispersibility, and adhesion. The viscosity, dispersibility, and adhesion were chosen as the parameters for the formula optimization. The cream of calabash ethanolic extract was shown as green, homogeneous semi-solid with a soft texture and distinctive aroma, and was an oil-in-water (O/W) type cream. The average pH of 5.6 was suitable for facial skin. The viscosity value increased with increasing surfactant concentration while dispersibility decreased. The results of formula optimization obtained the optimum formula was FIII with a concentration of Cremophor RH 40 of 15% and a desirability value of 0,896.

A comparative study of surfactant distribution and fate (western and eastern) Egyptian Mediterranean coasts focusing on its environmental toxicity

One of the most difficult-to-manage new contaminants constantly released into the environment is linear alkylbenzene sulphonate (LAS), an anionic surfactant. Significant volumes of LAS are received by the Mediterranean coast of Egypt. The current study is a comprehensive assessment of the environmental fate of the LAS 1505 km off the Mediterranean coast of Egypt in the fall of 2023 in order to track its geographic spread and eventual demise in the water column. Critical analysis of LAS revealed that it is vertically distributed in various ways according to sources, uses, production amounts, and salinity levels. The vertical variation of LAS can be explained by its amphiphilic structure. A significant increase in surfactant concentration (>300 μg/L) was recorded in 66% and 43% of the total samples, ranging from 301.128 to 455.36 and from 304.556 to 486.135 for the western and eastern sides along the Egyptian Mediterranean coast, respectively. Evaluation of the average acute and chronic risk quotient (RQ) along the investigated locations revealed that fish were the most susceptible to LAS in both long and short exposure periods. The presented results also indicated significant LAS toxicity to three trophic levels (RQ values > 1). LAS toxicity to marine organisms was greater in the western than in eastern coastal regions according to acute and chronic mixture risk characterization ratios (RCRmix). The three trophic levels in the study area had the following order of acute relative contribution (RC) to LAS toxicity: fish > invertebrates > algae. The ANOVA test results showed that in both the western and eastern regions, LAS varied significantly (p < 0.05) with salinity (1.04E-60 and 5.44E-42) and depth (6.02E-65 and 1.59E-47), respectively. In addition, a significant difference was observed using the ANOVA test between the eastern and western regions of the Egyptian Mediterranean coast.

Demulsification of surfactant-rich emulsion systems by using amphiphilic or positively charged magnetic nanoparticles

Emulsified oily wastewater comes from many fields, such as oil exploitation, processing, storage and transport, mechanical processing and food and catering industries, causing serious environmental pollution. Considerable part of emulsified oily wastewater was extremely stable and difficult to be treated due to the existence of high-concentration surfactants. Magnetic demulsification of oil-in-water (O/W) emulsion by using magnetic nanoparticles (MNPs) attracted more and more attentions because of its flexible and efficient process; however, the study regarding the treatment of emulsified oily wastewater containing high-concentration surfactant was still few. In this study, amphiphilic dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DOTAC)-coated MNPs (M-DOTAC) and hydrophilic but highly positively charged quaternized chitosan (QC)-coated MNPs (M-QC) were employed to treat the O/W emulsions containing various contents of anionic and nonionic surfactants. Influence of surfactant type and concentration on the demulsification performance of the two MNPs was investigated in detail. Results showed that M-DOTAC could more effectively demulsify the nonionic surfactant-stabilized emulsion mainly via hydrophobic interaction, while M-QC could more efficiently demulsify the anionic surfactant-stabilized emulsion mainly via electrostatic interaction. With increasing surfactant concentration, the MNPs were still able to completely demulsify the emulsion at a relatively higher dosage. Moreover, when the two classes of MNPs were used together, highly stable emulsion system with containing both anionic and nonionic surfactants could be completely demulsified. These results suggested the synthesized two MNPs could provide simple but powerful approach to treat different emulsified oily wastewaters with containing high-concentration surfactants.

Characterization of Surfactant Adsorption Profile in Carbonates Under Severe Reservoir Conditions With Geochemical Modeling Approach

Abstract Chemical flooding has gained ample popularity as an effective technique to increase oil displacement and sweep efficiencies. However, very limited numerical applications of chemical flooding (surfactant and polymer) in carbonates are reported in the literature. Therefore, a geochemical-based surface complexation model is developed to characterize the adsorption profile of surfactants for the first time across the length of a core/reservoir. The proposed model is validated with various zeta-potential measurements and also with a recently conducted chemical flooding study. Additionally, sensitivity analysis of various parameters is performed, and it is found that surfactant effluent concentration decreases with the increase in flood temperature. It is observed that salinity reduction decreases the surfactant adsorption, increases the ionic repulsion amid the rock surface charge and the chemical species polarity. Similarly, when the concentration of surfactant is increased, the adsorption of surfactant concentration increases. However, the increase in surfactant adsorption is insignificant. The effect of sulfate spiking in chemical flooding is also investigated and it is found that an increase in sulfate concentration reduces the adsorption of surfactant across the reservoir. Moreover, the lowermost surfactant adsorption level is achieved through the injection of diluted water (&amp;lt;0.1 mg/g).

Investigation on foam properties of Gemini quaternary ammonium salt containing hydroxyl hydrophilic headgroup

Four Gemini quaternary ammonium salts, tetramethylene-1,4- bis [N, N-bis(hydroxypropyl)-hexa/decyloxypropylammonium] bromide (GC6/10-P) and tetramethylene-1,4-bis [N, N-bis(hydroxyethyl)-hexa/decyloxypropylammonium] bromide (GC6/10-E) were synthesized by two-step reactions. This study analyzes the foam properties, including foamability, foam stability, and foam size distribution, of GC6/10-P and GC6/10-E using the Foamscan method. The influence of surfactant concentration and gas flow rate on the properties of Gemini quaternary ammonium salt foam was also studied. Additionally, the relationship between surfactant structure and foam morphology in aqueous solutions was discussed. The results show that all four types of Gemini quaternary ammonium salt surfactants are low-foaming surfactants. The foam capacity (FC) sequence is as follows: GC10-E > GC10-P > GC6-E > GC6-P. The foamability and foam stability are enhanced with increasing surfactant concentration, which increases the adsorbed quantity of surfactant molecules at the air-water interface. The foam produced by GC6-P/E systems is the most unstable; the foam behaviors show faster Ostwald ripening and drainage process in aqueous system. It seems that 150–200 mL/min is an ideal air intake speed. The presence of hydroxyl in the molecular structure enhances the formation of hydrogen bonding between surfactants and water molecules, leading to greater molecular compactness. The results indicate that the foaming behavior of hydroxyl Gemini quaternary ammonium salts can be correlated with concentration and alkyl chains. Foamscan are proposed to research the foaming and foam stability behavior and provide a useful guide for evaluating the foamability of cationic surfactants-based systems, especially in the development of environmentally friendly foam systems suitable for low-foaming products.

Concentration Dependent Asymmetric Synergy in SDS-DDAO Mixed Surfactant Micelles.

We investigate the structure and interactions of a model anionic/amphoteric mixed surfactant micellar system, namely, sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine N-oxide (DDAO), employing SANS, FTIR, DLS, and pH measurements, in the range 0.1-100 mM total surfactant concentration and 0-100% DDAO. Increasing surfactant concentration is found to elongate the prolate ellipsoid micelles (RPolar ∼ 25-40 Å), accompanied by up to a 6-fold increase in micellar charge. The surfactant synergy, in terms of micellar charge and size, diffusion coefficient, solution pH, and headgroup interactions, was found to vary with concentration. At lower concentrations (≤50 mM), the SDS-DDAO ratio of maximum synergy is found to be asymmetric (at 65-85% DDAO), which is rationalized using regular solution theory, suggesting an equilibrium between Na+ dissociation, DDAO protonation, and counterion concentration. At higher concentrations, maximum synergy shifts toward the equimolar ratio. Overall, our study expands and unifies previous reports, providing a comprehensive understanding for this model, synergetic mixed micellar system.

Hydrothermal synthesis of hydroxyapatite crystals with and without seed crystals and surfactant

To the best of our knowledge for the first time the hydroxyapatite (HA) crystals were synthesized with different doses of HA seed crystals. HA crystals were synthesized from solutions containing the stoichiometric amounts of ammonium dihydrogen phosphate and calcium hydroxide. The various interactions of the NH4H2PO4 concentrations (0.5–5.5 Molar), surfactant {amino tris (methylene phosphonic acid) [N(CH2PO3H2)3] (ATMP)} [ATMP] concentrations (0–100 ppm), and HA seed crystals doses (0–50%) were investigated and their effects on the HA mean diameter and hardness were studied using the Box-Behnken experimental statistical design. Results have shown that no correlations were obtained between the mean diameters of the HA crystals and the obtained HA hardness. HA synthesis in the absence of surfactant resulted in formation of HA rod-like and/or tabular crystals whereas agglomerated crystals were obtained with surfactant. The results indicate that with increasing the % of HA crystal seed dose, an increase in the HA mean diameter was obtained. Moreover, with increase of surfactant concentration, a high increase in HA hardness was achieved. HA crystal particle sizes were ranged from about 11–18 µm whereas the crystallite sizes were ranged from 22 to 46 nm.

Molecular simulation of the effect of anionic surfactant on methane diffusion in coal

Coal seam water injection is one of the important means of coal mine disaster prevention and control, which helps to reduce gas concentration. Anionic surfactants can change the hydrophilicity of coal to enhance the wetting effect of coal seam water injection and inhibit the diffusion of methane. However, the research on the effect of surfactants on the diffusion process of methane is still relatively weak. In order to explore the influence mechanism of anionic surfactant on coal surface wettability and methane diffusion from a microscopic point of view. Using wiser coal model and two commonly used anionic surfactants, sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), the surfactant/water interface configuration, water/coal contact angle configuration and coal seam methane diffusion configuration were constructed. The interfacial stability of surfactant and water was discussed, and the wetting modification effect of surfactant on coal surface and the law of gas diffusion were analyzed. Finally, by studying the microscopic properties of each molecule in the simulation system, the adsorption mode of surfactants, the hydrophilicity of polar groups, the number of hydrogen bonds and the change of the pore volume in the coal seam system were analyzed, and the wetting modification mechanism of surfactants on coal surface and the inhibition effect of methane diffusion were discussed. The results show that with the increase of surfactant concentration, the interface formation energy is constantly enhanced, and the absolute value of electrostatic energy gradually increases, making the effect between surfactant and water stronger. The contact angle of coal surface under the action of SDS surfactant is the smallest, which is 36.230°, indicating that SDS surfactant has the best effect on the wettability of coal surface. The amount of methane diffusion in the surfactant action system decreased significantly compared with the pure water system, and the distribution of methane in the coal seam increased, indicating that the interaction between methane and coal is enhanced under the action of surfactant. With the increase of surfactant concentration, surfactant molecules are easier to spread on the surface of coal seam, and the wettability of coal surface increases. The research results can provide some research ideas and reference significance for anionic surfactants in the prevention and control of coal mine gas disasters.

Plant-Based Oil-in-Water Food Emulsions: Exploring the Influence of Different Formulations on Their Physicochemical Properties.

The global focus on incorporating natural ingredients into the diet for health improvement encompasses ω-3 polyunsaturated fatty acids (PUFAs) derived from plant sources, such as flaxseed oil. ω-3 PUFAs are susceptible to oxidation, but oil-in-water (O/W) emulsions can serve to protect PUFAs from this phenomenon. This study aimed to create O/W emulsions using flaxseed oil and either soy lecithin or Quillaja saponins, thickened with modified starch, while assessing their physical properties (oil droplet size, ζ-potential, and rheology) and physical stability. Emulsions with different oil concentrations (25% and 30% w/w) and oil-to-surfactant ratio (5:1 and 10:1) were fabricated using high-pressure homogenization (800 bar, five cycles). Moreover, emulsions were thickened with modified starch and their rheological properties were measured. The physical stability of all emulsions was assessed over a 7-day storage period using the TSI (Turbiscan Stability Index). Saponin-stabilized emulsions exhibited smaller droplet diameters (0.11-0.19 µm) compared to lecithin (0.40-1.30 µm), and an increase in surfactant concentration led to a reduction in droplet diameter. Both surfactants generated droplets with a high negative charge (-63 to -72 mV), but lecithin-stabilized emulsions showed greater negative charge, resulting in more intense electrostatic repulsion. Saponin-stabilized emulsions showed higher apparent viscosity (3.9-11.6 mPa·s) when compared to lecithin-stabilized ones (1.19-4.36 mPa·s). The addition of starch significantly increased the apparent viscosity of saponin-stabilized emulsions, rising from 11.6 mPa s to 2117 mPa s. Emulsions stabilized by saponin exhibited higher stability than those stabilized by lecithin. This study confirms that plant-based ingredients, particularly saponins and lecithin, effectively produce stable O/W emulsions with flaxseed oil, offering opportunities for creating natural ingredient-based food emulsions.

Effect of Surfactant Concentration on Physicochemical and Antibacterial Properties of Eugenol Nanoemulsions

Introduction:: Nanoencapsulation has gained popularity in recent decades due to its numerous benefits, such as improved stability, oxidation resistance, retention of volatile ingredients, controlled release, delivery of multiple active ingredients in a row, improvement in organoleptic properties, reduction of toxic side effects, and water solubility. Methods:: The present study was aimed to prepare eugenol nanoemulsions (EuNEs) using non-ionic surfactant (Tween 80) by ultrasound-assisted techniques and to evaluate the effects of surfactant concentration on their droplets size, polydispersity index (PDI), zeta potential, storage stability, antioxidant, and antibacterial activities. Antimicrobial activity of the prepared nanoemulsions was tested against Gram-positive; Staphylococcus aureus, Bacillus subtilis and Gram-negative; Escherichia coli, and Alcaligenes faecalis bacteria using well diffusion method. Results:: The results showed that the droplet size decreased after a threshold Tween 80 concentration (10%), while PDI value increased with the increase in surfactant concentration (Tween 80). method: The droplets size, poly dispersity index (PDI), zeta potential, storage stability, antioxidant, and antibacterial activities of the prepared nanoemusions were characterized. Conclusion:: The prepared EuNEs exhibited good antibacterial activity against all the four bacterial strains: E. coli, A. faecalis, S. aureus, and B. subtilis. conclusion: No phase separation, creaming, layering or deposition of large oil droplet were observed in the prepared nanoemulsions (EuNE-5, EuNE-7.5, and EuNE-10) except in case of 15%, v/v Tween 80 (EuNE-15) during 30 days of storage

Synchronous magnetization to weaken the hindrance of surfactants to droplet coalescence during electric dehydration

Electric dehydration is the most widely used physical technology for separating water from crude oil. However, natural surfactants stabilize the oil–water interface, resulting in low dehydration efficiency and failure of the electric dehydrator due to electric field collapse. To explore the physical methods of weakening the influence of surfactants on electric dehydration, this study synchronously increased magnetization during the electric dehydration. Based on high-speed microscopy experiments, it has been demonstrated that synchronous magnetization weakens the hindrance of surfactants to droplet coalescence during electric dehydration. Within the experimental conditions, the influence of magnetization on the growth coefficient C1 ranges from 2.9% to 26.6%. In addition, based on molecular dynamics simulation, the mechanism of magnetization weakening the influence of surfactants was studied at the molecular level. It was found that water molecules and surfactant molecules undergo significant molecular clusters after magnetization, reducing the influence degree of surfactants on unit area. When the surfactant concentration increases, the decrease in the influence degree is balanced by the increase in the number of molecules, which also explains the law that the improvement rate ΔC1 decreases with the increase in surfactant concentration. The results of this work will be potentially valuable for weakening surfactant barriers to demulsification and oil–water separation.

Synthesis and electrochemical evaluation of nickel hydroxide nanosheets with phase transition to nickel oxide.

Transition metal hydroxides are commonly used to develop nanostructures with desired functionalities by controlling their size, morphology, and structure. In this study, nickel hydroxide nanosheets with a hexagonal island shape are synthesized via a surfactant-assisted method. Using this method, nickel hydroxide nanosheets can be easily achieved in a quick manner. The synthesized nanosheets are 3-6 nm thick and exhibit a curly and wrinkled morphology with increasing surfactant concentration. These nanosheets demonstrate superior catalytic properties for the oxygen evolution reaction activity compared to nickel oxide sheets obtained via a simple heat treatment. Furthermore, we conduct surface enhanced Raman scattering analysis to confirm that the nickel hydroxide nanosheets serve as active species for NiOOH during the oxygen evolution reaction, and we propose an electrochemical mechanism for this system. This study not only presents the detailed synthesis process but also proposes a straightforward approach, offering valuable insights into the structural and electrochemical properties of the resulting nanosheets.

Controlling the size and adhesion of DNA droplets using surface- enriched DNA molecules.

Liquid droplets of biomolecules serve as organizers of the cellular interior and are of interest in biosensing and biomaterials applications. Here, we investigate means to tune the interfacial properties of a model biomolecular liquid consisting of multi-armed DNA 'nanostar' particles. We find that long DNA molecules that have binding affinity for the nanostars are preferentially enriched on the interface of nanostar droplets, thus acting as surfactants. Fluorescent measurements indicate that, in certain conditions, the interfacial density of the surfactant is around 20 per square micron, indicative of a sparse brush-like structure of the long, polymeric DNA. Increasing surfactant concentration leads to decreased droplet size, down to the sub-micron scale, consistent with droplet coalesence being impeded by the disjoining pressure created by the brush-like surfactant layer. Added DNA surfactant also keeps droplets from adhering to both hydrophobic and hydrophilic solid surfaces, apparently due to this same disjoining effect of the surfactant layer. We thus demonstrate control of the size and adhesive properties of droplets of a biomolecular liquid, with implications for basic biophysical understanding of such droplets, as well as for their applied use.

Aqueous submicron dispersions of surfactants as wetting agents and permeability enhancers of potato leaves

For aqueous solutions and submicron dispersions of non-micelle-forming surfactants (Tween 85, Brij L4, and Silwet L-77) kinetic tensiometric dependences and isotherms of wetting of leaves of the Prime potato variety were obtained. A technique has been developed for determining the rate of penetration of the studied liquids into potato leaves. The rate of penetration rises with increasing surfactant concentration. An increase in permeability and wetting efficiency is observed as following: Tween 85 &lt; Brij L4 &lt; Silwet L-77. The data obtained make it possible to evaluate the prospects for using the studied aqueous surfactant dispersions as platforms for the delivery of biologically active components into the leaves of potato plants to inhibit the proliferation of pathogens.

Effect of surfactant frequently used in soil flushing on oxygen mass transfer in micro-nano-bubble aeration system

In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites. The surfactant presented in flushing solutions is bound to affect the aeration efficiency. The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble (MNB) aeration system. Firstly, bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble (dBS), gas holdup (ε), volumetric mass-transfer coefficient (kLa) and liquid-side mass-transfer coefficient (kL) in the MNB aeration system. Then, based upon the experimental results, the Sardeing’s and Frössling’s models were modified to describe the effect of surfactant on kL in the MNB aeration. The results showed that, for the twenty aqueous surfactant solutions, with the increase in surfactant concentration, the value of dBS, kLa and kL decreased, while the value of ε and gas–liquid interfacial area (a) increased. These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions. In addition, with the presence of electric charge, MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions. Furthermore, the accumulation of surfactant on the gas–liquid interface was more conspicuous for small MNB, so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions. Besides, the modified Frössling’s model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.

Damping effect of surfactants on induced bubble shape deformations

The addition of surfactants suppresses interfacial deformations, and surface elasticity is expected to play a critical role. High-speed imaging is used to study the influence of surfactants on the shape oscillations of air bubbles attached to a capillary and on the rebound of bubbles from a horizontal glass plate. The experiments are conducted in pure water and in aqueous solutions containing five different surfactants: terpineol, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, Triton X-100, and Triton X-45. The frequencies and damping times of the decaying oscillations and the restitution coefficients of the decaying rebounds are evaluated. The damping time and the restitution coefficient both decrease sharply with an increasing surfactant concentration and then reach a minimum before finally stabilizing. The oscillation frequency initially increases due to enhanced surface elasticity but then drops suddenly when the surfactant concentration corresponding to the maximum damping is reached. The suppression of bubble rebounds by surfactants bears a strong resemblance to the damping of quadrupole bubble oscillations. In both cases studied, a surface elasticity of about 4 mN/m is required to achieve the maximum damping of interfacial deformations, regardless of the surfactant used. Moreover, the bubble rebounds are found to be more susceptible to the presence of trace concentrations of surfactants.

Complete biodegradability assessment of polyoxyethylene glycerol ester non-ionic surfactant: Aerobic, anaerobic, combined biodegradation and inhibitory effects

Aerobic and anaerobic biodegradability have become one of the most relevant characteristics for all contaminants. This is especially important in case of surfactants, which are discharged in wastewater treatment plants or directly into the aquatic bodies. The aim of this study is the integral assessment of the biodegradability of the non-ionic surfactant polyoxyethylene glycerol ester PGE-OE17. The aerobic and anaerobic biodegradation of PGE-OE17 was evaluated at different initial surfactant concentrations, and the evolution of the toxicity of the surfactant and its by-products was followed during the aerobic and anaerobic processes using bacteria Vibrio fischeri. PGE-OE17 was not completely biodegradable neither aerobically nor anaerobically, and the increase in the initial surfactant concentration had a negative effect in the biodegradation. Toxicity of the surfactant solutions and degradation by-products had a first increase followed by a gradual decrease during both tests, revealing that toxic substances released can harm the microorganisms and therefore hinder the biodegradation. Additionally, combined aerobic-anaerobic biodegradation tests were performed, consisting in a first aerobic treatment of different duration and initial concentration, followed by a complete anaerobic treatment. Results showed that a balance between aerobic and anaerobic biodegradation duration can maximize the biodegradation rates in comparison with only aerobic or anaerobic tests.

Research by choice of excipients ingredients of the gel for the therapy of radiation lesions of the skin based on rheological studies

The aim of this work is to conduct a research analysis of changes in the structural and mechanical properties of the gel from the addition of active substances and surfactants.&#x0D; Materials and methods. In the presented work, model samples of the gel with active substances were studied: freshly obtained stonecrop juice, sea buckthorn oil, rosehip oil, St. John's wort oil and quercetin. As substances for the manufacture of bases hydrocolloids of cellulose derivatives were used: sodium carboxymethylcellulose (NaCMC) and hydroxyethylcellulose (HEC) with a surfactant Lanette SX.&#x0D; A study of the rheological properties of the samples was performed using a rheoviscometer Rheolab QC (Anton Paar, Austria) using a system of coaxial cylinders C-CC27 / SS. The Rheolab QC rheometer is equipped with RheoPlus software, which allows you to set the necessary experimental conditions (shear rate gradient range, number of measuring points and measurement time of one point).&#x0D; Results. The rheological properties of model samples of NaCMC and HEC gels, depending on the used concentration, were studied. With increasing concentrations of both NaCMC and HEC thixotropy of dispersed systems decreases. The change of structural and mechanical parameters of hydrogels from the addition of active ingredients and surfactant is analyzed, and established that adding them into the hydrogels increases the structural and mechanical parameters of model samples.&#x0D; A study of gels with a constant concentration of sodium carboxymethylcellulose and hydroxyethylcellulose and different content of surfactant Lanette SX established that as the surfactant concentration increases, the area of the hysteresis loop and the resistance of the dispersed system to the applied mechanical fracture increase.&#x0D; Conclusions. According to the results of the obtained structural and mechanical parameters and rheograms of the studied model samples of gels, it is rational to use in further studies of sodium carboxymethyl-cellulose (1.5 %) and hydroxyethylcellulose (1.25 %) stabilized Lannete SX in concentrations of 4-5 % and 3-5 % respectively