Journal of Surfactants and Detergents最新文献

Surface properties of three fluorocarbon surfactants with different carbon chain lengths were studied at low pressures of 94.6, 74.1 and 61.0 kPa, respectively. The results showed that the saturation adsorption capacity and the critical micelle concentration (CMC) decreased, while the average molecular area (A_S) and the surface tension at CMC (γ_CMC) of fluorocarbon surfactants increased with decreasing pressure. The surface tension (γ) decreased with the decrease of pressure when the concentration of fluorocarbon surfactants was low. However, γ tended to be stable and increased with the drop of pressure when the concentration of surfactants was close or reach to CMC. In addition, the foaming and spreading performance of fluorocarbon surfactants decrease with the decrease of pressure, and the combination of fluorocarbon and hydrocarbon surfactants is beneficial to the improvement of performance (mixed systems: foam expansion E>6, 25% drainage time t_25%>241 s, 1/2 defoaming time t_1/2>851 s, spreading amount V_s>223 μL, spreading time t_s<2 s). Further fire extinguishing experiment found that the influence of low pressure environment on fuel combustion characteristics is the key factor to determine fire extinguishing performance, while the influence of aqueous film-forming foam (AFFF) performance is small. And AFFF based on the environmental-friendly surfactant C₄F₉SO₂NH(CH₂)₂N⁺(CH₃)₂CH₂BrCH₂OH (FC-4) is an effective fire extinguishing agent under low pressure.

Many surfactants, such as higher mole alcohol ethoxylates like C12-15–7EO and C9-11–8EO, when diluted in water, will form a gel at specific concentrations and temperatures. Gels can be highly viscous and semi-solid and should be avoided since they take time and energy to disperse once formed. Historically, the creation of gel diagrams or maps for our technical product brochures primarily has depended on visual observation, leading to variable interpretations and inconsistent results over time. Also, completing a gel map for one surfactant grade requires a minimum of one day, due to testing many samples across various concentrations and temperatures. To improve objectivity, consistency, and speed in gel mapping, oscillatory rheology was utilized to identify gels using viscoelastic properties by testing samples prepared at various concentrations. The digitization of the gel mapping technique provides two significant benefits. It offers a rheological-based approach giving a non-subjective, digital gel map and it is faster than our visual-based method. Furthermore, this digital method is consistent with our visual-based method giving good discrimination between surfactant grades and reproducibility within batches of the same grade. This work also demonstrates the promising potential of utilizing machine learning algorithms to model the rheological behavior of gel maps effectively. R and Python, programming languages widely used for data analysis, graphing, and machine learning, were employed. Overall, the new digital approach presented yields several benefits for surfactant gel behavior study, including a reduction in subjectivity, faster data generation, and increased efficiency in the gel map analysis process.

Biosurfactants are amphiphilic molecules containing one hydrophilic and one hydrophobic moiety. They are synthesized by microorganisms either on the cell surface or secreted extracellularly which serve as natural surfactant substitutes with a wide range of applications in different sectors. The present study aims to assess the antioxidant, antimicrobial, and antibiofilm properties of biosurfactants derived from Enterococcus faecalis BHT-2 against different microorganisms (E. clocae, P. aeruginosa, M. luteus, S. aureus, C. albicans, and E. coli). Derived biosurfactants showed antimicrobial activity against test microorganisms in the range between 0.6 and 3 mg/mL. It displayed potent antibiofilm ability by inhibiting the bacterial attachment to surfaces, leading to the disruption of biofilm formation by altering the integrity of microbial biofilms when observed on coverslips by SEM and fluorescence microscopy. The treatment of microbial biofilms by biosurfactants greatly reduced the exopolysaccharide biomass, that is, carbohydrate and protein content. Thus, in vitro assessment of antimicrobial and antibiofilm properties of biosurfactants derived from E. faecalis BHT-2 indicated that it act as a better alternative antimicrobial agents.

This research studied the wastewater chromium removal efficiency by dissolved air flotation (DAF) using a rhamnolipid (RL) biosurfactant as a collector. An experimental flotation DAF apparatus with 6 vessels of 2 L containing a coupled saturator injecting compressed air at 5.88 kPa in the vessels was used. The total RL concentration of the broth resulting from fermentation was 9 ± 1.0 g/L. This broth was used in nature in the DAF experiments. A central composite design (CCD) was used to optimize removal of Cr(VI) and total Cr with regards to two independent variables, pH (3.17–8.83) and iron concentration of the medium (0–225.0 mg/L), with a three assays performed at the conditions of the central point of the design. The experimental conditions for DAF were an initial hexavalent Cr concentration of 100 mg/L; RL broth volume of 500 mL; saturated with oxygen water volume of 200 mL; and a rapid mixing time of 6 min through stirring at 120 rpm. The results showed that under acidic pH conditions and with high iron concentrations, both the Cr(VI) and total Cr removal rates were highest. The optimal removal region determination was at a pH of 3.5 and iron concentration of 180 mg/L. Subsequently, cationic tannin-based flocculant was also evaluated as a collector, and ferrous sulfate was used as a coagulant during Cr(III) removal. The best Cr(III) removal percentage was obtained at cationic polymer concentrations of 300 mg/L with Cr(III) removal of 50.8% and a pH of 5.5.

Ethoxylation is one of the common industrial process in which ethylene oxide (EO) is added to compounds containing active hydrogen atom (OH, COOH, SH, NH, etc.) to form surfactants. Alcohol ethoxylates are a major class of non-ionic surfactants composed of an alkyl chain combined with few EO units. They are widely used in homecare products, personal care products, textiles, oilfield, construction, lubricants, food, paper, leather. The analysis of these ethoxylates possess several challenges since they contain ‘n’ number of EO units (n > 1). With increase in “n,” the product becomes more and more viscous and the boiling point increases making it difficult to analyze by normal gas chromatography (GC) technique. This paper describes a method of derivatizing these ethoxylates so that they can be eluted on a high temperature GC. BSTFA (N, O-bis (trimethylsilyl) trifluoroacetamide) is used as the derivatizing agent (silylating agent). The ethoxylate combines with BSTFA to form the corresponding trimethylsilylated (TMS) product, which have comparatively lower boiling point. Thus, we detect trimethyl silyl product, which is the resemblance for the ethoxylated product. In this paper, we present a quantitative GC method for the ethoxylates of a few simple alcohols (2-ethyl hexanol, glycerin), and complex vegetable oils (castor oil). The products formed during the reaction have also been identified on a gas chromatograph coupled with mass spectrometer (GCMS). GCMS shows the mass corresponding to the TMS derivatized product. The derivatization technique not only helps in increasing the volatility of these compounds but also improves the chromatographic efficiency, selectivity, and enhances the detectability.

The lyotropic properties of alkyl thioglycosides with varying sugar headgroup (lactose, cellobiose, maltose, galactose, or glucose) and alkyl chain length (octyl, decyl, or dodecyl chains) are investigated by surface tensiometry, visual observation, and fluorescence spectroscopy. The results substantiate that the glycosidic S-linkage confers considerably different solution aggregation behavior on these surfactants relative to their O-linked counterparts, where the properties of the latter are known. The materials properties of the aggregated structures from the alkyl thioglycosides vary considerably. Micelles are formed by octyl thiocellobioside and all alkyl thiomaltosides. Turbid aggregate solutions are formed by the alkyl thioglucosides and octyl thiogalactoside, whereas the longer chain alkyl thiogalactosides are minimally soluble. Fluorescence spectroscopy of these systems confirms their aggregation in lamellar-like structures. The alkyl thiocellobiosides and alkyl thiolactosides form hydrogels from these low-molecular weight materials at concentrations almost an order of magnitude lower than gels using other low-molecular weight materials. Here, hydrogels form at concentrations <0.3 wt% with some forming hydrogels at concentrations as low as 0.03 wt% from alkyl thiocellobiosides and thiolactosides, with hydrogel properties differing significantly with this slight change in the sugar headgroup. Alkyl thiocellobiosides form a nanofiber network and alkyl thiolactosides form globular hydrogels. Overall, these results clearly document materials properties that can readily be controlled and designed depending on molecular structure.

Myelin figures (MFs)—cylindrical lyotropic liquid crystalline structures consisting of concentric arrays of bilayers and aqueous media—arise from the hydration of the bulk lamellar phase of many common amphiphiles. Prior efforts have concentrated on the formation, structure, and dynamics of myelin produced by phosphatidylcholine (PC)-based amphiphiles. Here, we study the myelinization of glycolipid microbial amphiphiles, commonly addressed as biosurfactants, produced through the process of fermentation. The hydration characteristics (and phase diagrams) of these biological amphiphiles are atypical (and thus their capacity to form myelin) because unlike typical amphiphiles, their molecular structure is characterized by two hydrophilic groups (sugar, carboxylic acid) on both ends with a hydrophobic moiety in the middle. We tested three different glycolipid molecules: C18:1 sophorolipids and single-glucose C18:1 and C18:0 glucolipids, all in their nonacetylated acidic form. Neither sophorolipids (too soluble) nor C18:0 glucolipids (too insoluble) displayed myelin growth at room temperature (RT, 25°C). The glucolipid C18:1 (G-C18:1), on the other hand, showed dense myelin growth at RT below pH 7.0. Examining their growth rates, we find that they display a linear $��L��\alpha ��t�$ (L, myelin length; t, time) growth rate, suggesting ballistic growth, distinctly different from the $��L��\alpha ��t^{\frac{1}{2}}�$ dependence, characterizing diffusive growth such as what occurs in more conventional phospholipids. These results offer some insight into lipidic mesophases arising from a previously unexplored class of amphiphiles with potential applications in the field of drug delivery.

Storing thermal energy and using renewable energy are some of the most important challenges humanity faces today. Using phase change materials (PCM) is a suitable solution to prevent heat loss. PCM emulsions (PCMEs) have several advantages and are specifically applied in heat exchangers. Here, the formulation of these emulsions, the type of surfactants, and their composition based on freeze–thaw cycle stability are investigated. The Hydrophilic–Lipophilic-Deviation (HLD) platform is used for this purpose. Considering the importance of stability during temperature changes in PCMEs, three types of surfactants that have different behaviors with respect to temperature are used: ethoxylates, ionics, and sugar-based surfactants. By performing freeze–thaw cycles on emulsions made by individual surfactants, after 10 freeze–thaw cycles it was observed that the oil separation in each of the samples containing polysorbate80, AOT, lauryl-myristyl-alcohol-polyethylene-glycol-ether, SDS, sorbitan-monooleate, and decylglucoside occurred at the 2nd, 4th, 6th, 7th, 8th, and 10th-cycle, respectively. Therefore, the sorbitan-monooleate and decylglucoside had better freeze–thaw cycle stability compared to the others because of their non-sensitivity to temperature. We also applied the emulsion cycle stability with two combinations of surfactants: (1) polysorbate80 and sorbitan-monooleate, (2) decylglucoside and sorbitan-monooleate. The former, despite the effect of temperature, showed no oil phase separation in the nine freeze–thaw cycles, but in the latter, the oil phase separation occurred in the 5th-cycle. This study shows that synergism of surfactants is the most important factor in the stability of emulsions. To better explore these emulsion systems, the storage stability, freeze–thaw stability, droplet morphology, and viscosity tests were performed on different samples at various HLD values.

A series of carboxylated carbosilane surfactants with methyl, ethyl, branching CH₃, phenyl, and cyclohexyl (Me-Si₂C-COONa, Et-Si₂C-COONa, Si₂C-La-COONa, Ph-Si₂C-COONa, and Cy-Si₂C-COONa) were prepared. The effect of isomer and steric hindrance on their micellization in aqueous solution was investigated by surface tension, conductivity, transmission electron microscopy (TEM) and dynamic light scattering (DLS). Si₂C-La-COONa with branching CH₃ shows a lower γ_CMC value and higher the CMC value compared with Et-Si₂C-COONa. Cy-Si₂C-COONa with cyclohexyl (41.6 mN m⁻¹) and Ph-Si₂C-COONa with phenyl (43.9 mN m⁻¹) have larger γ_CMC values due to the distinct steric hindrance and hydrophobicity. In aqueous solution, the aggregation behavior of Si₂C-La-COONa, Cy-Si₂C-COONa, and Ph-Si₂C-COONa is enthalpy-driven. However, the micellization process of Me-Si₂C-COONa and Et-Si₂C-COONa is governed by the enthalpy-driven at high temperature and entropy-driven at low temperature. DLS and TEM results indicate that the carboxylated carbosilane surfactants can self-assemble into aggregate with hydrodynamic diameters of 50–400 nm.

The micellization behavior of conventional cationic surfactant: tetradecyltrimethylammonium bromide (TTAB), and Gemini surfactant (GS): N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-ethanediyl-diammonium dibromide (14-2-14) in water and water-trifluoroethanol (TFE) solvent mixture has been examined using tensiometric and small-angle neutron scattering (SANS) techniques. Critical micelle concentration (CMC), and various interfacial parameters such as surface tension at CMC (γ_CMC), surface pressure at CMC (π_CMC), maximum surface excess concentration (Γ_max), and minimum area occupied by the head group (A_min) were evaluated for our examined systems at 303.15 K. It was observed that with the increase in TFE concentration, the CMC of the tested cationic surfactants decreased, thereby favoring the micellization in the presence of the surface-active TFE. Furthermore, the geometry and aggregation number (N_agg) of surfactant micelles were inferred using SANS that revealed the decrease in micelle size of cationic surfactants. Additionally, the computational simulation study provided an insight into the molecular interactions in the examined system that validated our experimental findings.