Linear Surfactants Research Articles

Coal-Based Branched Vicinal Diol Ethoxylates Versus Guerbet Alcohol Ethoxylates: Role of Tertiary Hydroxyl Groups.

Branched surfactants exhibit a lower surface tension, excellent low defoaming performance, and better wetting ability compared with linear surfactants, making them promising for applications in industrial cleaning. In this study, 2-hexyl-1-decene (C8 olefin dimer), obtained from the dimerization of 1-octene, was used as the hydrophobe to synthesize branched nonionic surfactants via hydroxylation and ethoxylation. The hydroxylation of the C8 olefin dimer to synthesize 2-hexyldecane-1,2-diol (C8 BD) using H2O2 and HCOOH was investigated systematically. Under the optimal reaction conditions (H2O2/C8 olefin dimer molar ratio: 1.5, HCOOH/C8 olefin dimer molar ratio: 4.0, reaction time: 10 h, reaction temperature: 50 °C), the conversion of the C8 olefin dimer and selectivity toward C8 BD were found to reach 99.96 and 79.89%, respectively. Further, branched nonionic surfactants (C8 BDEn) were synthesized via ethoxylation of C8 BD with ethylene oxide and characterized using FTIR, LCMS, 1H NMR, and 13C NMR techniques. The presence of a tertiary hydroxyl group in C8 BD increases the reactivity of the primary hydroxyl group, leading to a narrower range of products and lower residual substrate content. The physicochemical properties and surface properties of C8 BDEn with different degrees of ethoxylation at various concentrations were investigated and compared with those of commercially available Guerbet alcohol polyoxyethylene ethers (C8 GAEO9 and C6 GAEO9). The results show that, compared with C8 GAEO9 and C6 GAEO9, C8 BDE6 displayed a higher surface activity with a lower equilibrium surface tension (27.14 mN·m-1), superior wettability with a smaller contact angle (39.2°), better emulsification performance with a longer emulsification time of 548 s, and excellent foaming properties (initial foam volume of 11.6 mL). This strategy of utilizing coal-based α-olefins for the synthesis of branched nonionic surfactants presents a route to prepare value-added fine chemicals from coal-based resources.

Synergisms between Surfactants, Polymers, and Alcohols to Improve the Foamability of Mixed Systems

In order to produce detergents with improved performance and good market acceptability, it is crucial to develop formulations with improved foamability and cleaning performance. The use of a delicate balance of surfactants and additives is an appealing strategy to obtain good results and enables a reduction in the amount of chemicals used in formulations. Mixtures of hydrophobically modified linear polymers and surfactants, as well as balanced mixtures with co-surfactants and/or hydrotropes, are the most effective parameters to control foamability and foam stability. In the present study, the effect of the addition of hydrophobically modified linear polymers, nonionic co-surfactants and hydrotropes, and their mixtures to anionic and zwitterionic surfactant aqueous solutions was evaluated. It was found that the presence of the hydrophobically modified polymer (HM-P) prevented the bubbles from bursting, resulting in better stability of the foam formed using zwitterionic surfactant solutions. Also, the surfactant packing was inferred to be relevant to obtaining foamability. Mixtures of surfactants, in the presence of a co-surfactant or hydrotrope led, tendentially, to an increase in the critical packing parameter (CPP), resulting in higher foam volumes and lower surface tension for most of the studied systems. Additionally, it was observed that the good cleaning efficiency of the developed surfactant formulations obtained a higher level of fat solubilization compared to a widely used brand of commercial dishwashing detergent.

Effect of linear anionic surfactant (sodium dodecyl sulfate) dosage on nitrogen removal performance of an anammox reactor

AbstractThe impact of sodium dodecyl sulfate (SDS, as model linear anionic surfactant) dosage on overall nitrogen removal performance of anammox reactor alongside its microbial population and sludge properties was investigated. In this study (day 136), an anmmox sequencing batch biofilm reactor was subjected to gradual dosage of SDS from 0 to 20 mg L−1. Intriguingly, results revealed that SDS at ≥7.5 mg L−1 prompted sludge disintegration, evidenced by increased protein and polysaccharide content in the effluent. Nevertheless, reactor's average total nitrogen removal efficiency slightly improved from 83.12% (0 mg L−1) to 86.3% (20 mg L−1). The 16S rRNA gene sequencing revealed that SDS dosing significantly suppressed the unwanted and unavoidable nitrite oxidizing bacteria (NOBs) in the reactor as the abundance of genus Nitrospira declined from 40.68% (day 1) to 19.15% (day 136). The abundance of anammox genus Candidatus Kuenenia significantly improved from 1.86% (day 1) to 40.02% (day 136) as a result of NOB suppression. This study revealed that low concentration of surfactants in wastewater does not affect the anammox bacteria in a biofilm reactor. Furthermore, adding low concentrations of SDS (≥7.5 to 20 mg L−1) to wastewater may effectively suppress notorious NOBs in biofilm‐based anammox systems.

Synergy between surfactants' stiffness and concentration on their self-assembly into reverse micelles as water droplet carriers in nonpolar solvents.

A study of the self-assembly process into reverse micelles (RMs) of linear surfactants and monomeric aqueous solutes dissolved in nonpolar solvents, varying the concentration (cs) and the persistence length (Lp) of the surfactants is presented here. The influence of cs and Lp on the structural and dynamic properties of the aggregates is investigated through mesoscopic simulations carried out with the dissipative particle dynamics method. All simulations are performed at a fixed water/surfactant molecular ratio of 2:1, varying the surfactant concentration from c = 6 wt% up to c = 12 wt%, for increasing surfactants' rigidity from Lp = 0.73 nm up to Lp = 44.99 nm. It is found that there exists a collaborative interplay between cs and Lp that enhances the number of RMs assembled and their diffusion as carriers of water droplets. These results should be useful as guidelines to understand and improve processes where the RMs are implemented to carry aqueous solutes in nonpolar solvents.

Glycyrrhizic acid aggregates seen from a synthetic surfactant perspective.

Bio- or plant-based surfactants are a sustainable and renewable alternative to replace synthetic chemicals for environmental, drugs and food applications. However, these "green" surfactants have unique molecular structures, and their self-assembly in water might lead to complex morphologies and unexpected properties. The micellization of saponin molecules, such as glycyrrhizic acid (GA), differs significantly from those of conventional synthetic surfactants, yet these differences are often overlooked. Saponins self-assemble in complex hierarchical helical morphologies similar to bile salts, rather than the expected globular, ellipsoidal and wormlike micelles. Here, we review two potential routes for molecular self-assembly of GA, namely kinetics of crystallization and thermodynamic equilibrium, focusing on their structure as a function of concentration. Some uncertainty remains to define which route is followed by GA self-assembly, as well as the first type of aggregate formed at low concentrations, thus we review the state-of-the-art information about GA assembly. We compare the self-assembly of GA with conventional linear surfactants, and identify their key similarities and differences, from molecular and chemical perspectives, based on the critical packing parameter (CPP) theory. We expect that this work will provide perspectives for the unclear process of GA assembly, and highlight its differences from conventional micellization.

Synthesis and evaluation of core–shell nanocomposites for the photodegradation of liner alkyl-benzene sulfonate water contaminations

Linear alkyl-benzene sulfonate surfactants (LAS) are a major pollutant source of sewage and wastewater. They trigger severe impact on the environmental fauna and flora. Current research explores the synthesis of three different core–shell nanocomposites (CSNCs) containing titania through an inexpensive oxidative polymerization technique. The fabricated CSNCs were evaluated for the photocatalytic degradation of LAS water contaminations. The selected CSNCs investigated for this study were the TiO2/poly(aniline-co-pyrrole) and TiO2/ poly(aniline-co-3-Me-thiophene) as well as the TiO2/terpolymer (aniline-pyrrole-m-aminobenzoic acid). The structure of the formed nanocomposites was confirmed by varied characterization spectroscopy. The core–shell structure of the nanocomposites was confirmed by scanning electron micrographs and transmission electron microscopy. The CSNCs exhibited intensive photo catalytic degradation efficacy toward LAS under visible light exposure in comparison with the exposure in their absence. The parameters optimizing their photovoltaic degradation efficiency were assessed. The presented approach implies that an effective, economical, and environmentally friendly synthetic setup was achieved to produce novel CSNCs with high potential as LAS photodegradation agents.

Investigating oil solubilization into nonionic micelles by Raman multivariate curve resolution

AbstractHydrophobic hydration, whereby water spontaneously structures around hydrophobic and amphiphilic molecules, plays a key role in the process of surfactant micelle formation and micellar oil solubilization. Using vibrational Raman multivariate curve resolution spectroscopy, we characterized changes in the hydrophobic hydration occurring within nonionic alkylphenol ethoxylate surfactant Tergitol NP‐12 micelles as a function of oil solubilization. We report trends in the changes of hydrophobic hydration depending on the chain length of the oil as well as the presence of a halogen atom in the oil chemical structure. Changes in hydrophobic hydration directly correlate to changes in the physical properties of the micellar solution, including cloud point and micelle hydrodynamic diameter. We compare hydrophobic hydration of Tergitol NP‐12 to nonionic linear alkyl ethoxylate surfactant Makon TD‐12 and ionic sodium dodecyl sulfate and observe similar trends; the molecular structure of the oil has the largest impact on the hydrophobic hydration. We believe these studies contribute to a fundamental understanding of the importance of hydrophobic hydration in surfactant and oil aggregates, especially as it relates to micellar oil solubilization, and provide insight into how the molecular solubilizate can impact micellar structure, size, and stability.

The effect of the molecular structure of hydroxypropyl methylcellulose on the states of water, wettability, and swelling properties of cryogels prepared with and without CaO2

Hydroxypropyl methylcellulose (HPMC) belongs to the cellulose ether family that has hydroxyl groups substituted by hydrophobic methyl groups (DS) and hydrophilic hydroxypropyl groups (MS). Herein, the interactions between water molecules and cryogels prepared with HPMC in the presence and absence of a linear nonionic surfactant, as well as CaO2 microparticles, which react with water producing O2, were systematically investigated by sorption experiments and Time-Domain Nuclear Magnetic Resonance. Regardless of the DS and MS, most water molecules presented transverse relaxation time t2 typical of intermediate water and a small population of more tightly bound water. HPMC cryogels with the highest DS of 1.9 presented the slowest swelling rate of 0.519 ± 0.053 gwater/(g.s) and the highest contact angle values 85.250o ± 0.004o, providing the best conditions for a slow reaction between CaO2 and water. The presence of surfactant favored hydrophobic interactions that allowed the polar head of the surfactant to be exposed to the medium, resulting in a higher swelling rate and lower contact angle values. The HPMC with the highest MS presented the fastest swelling rate and the lowest contact angle. These findings are relevant for the formulations and reactions, where tuning the swelling kinetics is crucial for the final application.

Highly selective cross ketonization of renewable acids over magnesium oxide

The rising demand for linear alkylbenzene surfactants (LAS) poses an environmental threat as LAS are industrially produced from petroleum using corrosive acid catalysts.

Flow of a concentrated emulsion with surfactant through a periodic porous medium

High-resolution, long-time three-dimensional simulations are presented for slow, pressure-driven flow of a periodic emulsion of deformable drops through a dense, simple cubic array of solid spheres (one drop and one particle per periodic cell). The drops, covered with insoluble, non-diffusive surfactant, are large compared with pores, and they squeeze with high resistance, very closely coating the solids to overcome surface tension and lubrication effects. The solid volume fraction is 50 %, the emulsion concentration $c_{em}$ in the pore space is 36 % or 50 %, the drop-to-medium viscosity ratio $\lambda$ is 0.25 to 4. The contamination measure $\beta \leq 0.1$ keeps the linear surfactant model (assumed in most of the work) physically relevant. The boundary-integral solution requires extreme resolutions (tens of thousands of boundary elements per surface) achieved by multipole acceleration with special desingularizations, combined with flow-biased surfactant transport algorithms for numerical stability. The time-periodic regime is typically attained after a few squeezing cycles; the motion period is used in the extrapolation scheme to evaluate critical capillary numbers $Ca_{crit}$ demarcating squeezing from trapping. Due to Marangoni stresses, even light ( $\beta =0.05$ ) to moderate ( $\beta =0.1$ ) contaminations significantly reduce the average drop-phase migration velocity (up to 2.8 times, compared with clean drops), especially at small $\lambda =0.25$ . In contrast, $Ca_{crit}$ is weakly sensitive to contamination and levels off completely at $\beta =0.05$ . At $\lambda =0.25$ and $c_{em}=0.36$ , the average drop-phase velocities are much different for lightly and moderately contaminated emulsions, except for near-critical squeezing when they become the same. Nonlinear surfactant models (Langmuir, Frumkin) are used to validate the linear model.

Interfacial behavior and emulsion stability of lipid delivery system regulated by two-dimensional facial amphiphiles bile salts

Bile salts as two-dimension facial amphiphile effectively emulsify lipids at low concentrations to promote gut digestion. Hence, we select various bile salts sodium cholate (NaC), sodium glycocholate (NaGC) and sodium taurocholate (NaTC) to study the interfacial tension and rheological dilational modulus to illustrate the interfacial adsorption mechanism and interface film strength, which is closely related to emulsion stability. Unlike linear surfactant molecules, the interfacial behavior of bile salts contains into two stages. At the low concentration for the first stage, the rigid facial molecules adsorb at the lipid-water interface with the hydrophilic concave and hydrophobic convex surface. And the interfacial relaxation is mainly dominated by intermolecular interaction and diffusion exchange, resulting in that the adsorption layer is especially an elastic film. During the second stage, aggregates are gradually generated at the interface as the concentration increases, and the interfacial relaxation is mainly dominated by the rapid diffusion exchange between the adsorption film and the sublayer, leading to the faster formation of the adsorption film. The mechanism of facial amphiphile adsorbed at lipid-water interface indicates soft molecular membrane established at interfaces on account of intermolecular interaction, revealing that higher interfacial strength benefits emulsion stability. We also found that NaTC with excellent adsorption capacity can stabilize edible oil for 8 h to facilitate lipid digestion. Compared with linear surfactant, bile salts with great biocompatibility can form two-dimension adsorption layer to emulsify and stabilize lipids, which can be widely used in lipid delivery system.

Adsorption and aggregation properties of homogeneous polyoxyethylene alkyl ether- and ester-type nonionic surfactants with multi-branched double chains

Homogeneous polyoxyethylene (EO) alkyl ether- and ester-type nonionic surfactants with multi-branched double chains were newly synthesized. Their adsorption and aggregation properties were investigated through cloud point, surface tension, and small-angle X-ray scattering measurements, and compared to those of homogeneous EO alkyl ether- and ester-type nonionic surfactants with symmetric and asymmetric linear double chains as well as a conventional surfactant with a linear single chain. The surface tension at the critical micelle concentration for the multi-branched double-chain type decreased considerably to 27.9–28.8 mN m−1 despite having a large hydrophilic group of EO12 when multi-branched methyl groups with low surface energy were used as the hydrophobic groups of the surfactants. In the temperature vs. concentration phase diagrams, the regions of lamellar liquid crystals were more extensive for the linear double-chain surfactants because of the small interfacial curvature induced by the steric hindrance of the multi-branched chains.

The persistence length of linear surfactants modulates the self-assembly of reverse micelles and their diffusion in nonpolar solvents

The self-assembly of linear model surfactants into reverse micelles (RMs) in a nonpolar solvent is studied here for two surfactant lengths, through numerical simulations.

Кинетические и активационные параметры реакции биохимического разложения додецилсульфата натрия в природной воде

The method of laboratory modeling was used to determine the rate constants, half-transformation periods, temperature coefficient, and free activation energy and activation enthalpy of the reaction of biochemical decomposition of sodium dodecyl sulfate in the water of the Petrozavodsk Bay of Lake Onega at different temperatures. The reaction rate constants increase from 0.064 ± 0.005 to 0.089 ± 0.006 day -1 with an increase in temperature from 10 to 20 °C, and the half-life periods respectively decrease from 10.8 ± 0.8 to 7.8 ± 0.6 days. Kinetic and activation parameters make it possible to calculate the rate of decomposition of synthetic linear anionic surfactants in natural water under changes in environmental conditions.

Shape and Structure Formation of Mixed Nonionic-Anionic Surfactant Micelles.

Aqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant micelles; the intermicellar interactions are modelled by using a hard-sphere Percus–Yevick (HS-PY) or a rescaled mean spherical approximation (RMSA) structure factor. Choosing these specific nonionic surfactants allows for comparison of the effect of branched (Tween20) and linear (BrijL23) surfactant headgroups, both constituted of poly-ethylene oxide (PEO) groups. The nonionic–anionic surfactant mixtures are studied at various concentrations up to highly concentrated samples ( ≲ 0.45) and various mixing ratios, from pure nonionic to pure anionic surfactant solutions. The scattering data reveal the formation of mixed micelles already at concentrations below the critical micelle concentration of SDS. At higher volume fractions, excluded volume effects dominate the intermicellar structuring, even for charged micelles. In consequence, at high volume fractions, the intermicellar structuring is the same for charged and uncharged micelles. At all mixing ratios, almost spherical mixed micelles form. This offers the opportunity to create a system of colloidal particles with a variable surface charge. This excludes only roughly equimolar mixing ratios (X≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions.

First Approach to Measure Interfacial Rheology at High-Pressure Conditions by the Oscillating Drop Technique

An oscillating drop rheometer capable of operating under conditions of high pressure and high temperature has been built. The oscillating drop mechanism was able to support pressures as high as 1300 bar and successfully performed oscillations at constant pressure. Apparent elastic and viscous complex moduli were measured for a system of CO2 and synthetic seawater containing 100 ppm of a linear alkyl ethoxylate surfactant for different pressures and temperatures. The moduli had strong dependencies on both pressure and temperature. At temperatures of 40 and 80 °C, the apparent elastic modulus passed through a maximum for pressures between 100 and 300 bar. The harmonic distortion of the oscillations was calculated for all measurements, and it was found that drop oscillations below ca. 2.6 µL caused distortions above 10% due to a mechanical backlash of the motor.

Studying the Properties of PVdF-HFP Based Lithium Polymer Electrolytes Using non-ionic Surfactants as Plasticizers

In this study, two different non-ionic surfactants have been evaluated as a plasticizer in lithium polymer electrolytes and compared with an organic carbonate-based plasticizer. To that end, non-ionic surfactants with different molecular weight and structure have been selected (Triton� X-100 and Brij�L23) and compared with organic carbonates (EC:DEC1:1) as plasticizers in lithium polymer electrolytes. The effect of the plasticizer content, salt content and surfactant characteristics on properties such as ionic conductivity, thermal stability and electrochemical stability of lithium polymer electrolytes has been studied. The results obtained show that the non-ionic surfactants studied as plasticizers (Triton� X-100 and Brij�L23) give lithium polymer electrolytes with higher thermal and electrochemical stability than organic carbonates, thus making them promising plasticizers for lithium polymer electrolytes, especially for high voltage lithium-ion batteries. Surfactant structure could influence the ionic conductivity of the polymer electrolytes, with the linear surfactants being more suitable for this application.

Self – assembly of model surfactants as reverse micelles in nonpolar solvents and their role as interfacial tension modifiers

The self-assembly of linear surfactants into reverse micelles (RMs) in nonpolar solvents, and their efficiency in reducing the interfacial tension is studied using dissipative particle dynamic simulations. Given the importance of RMs as thickeners, among many other applications, their properties are studied here when formed in oil and in supercritical carbon dioxide (scCO2). Our simulations are found to be in agreement with experimental results of surfactant self-assembly in scCO2 that found viscosity increments of up to 90% with 10 wt % of surfactants. The role played by a small number of water molecules in RM formation is studied as well in both solvents, corroborating experiments reporting the enhancement of RM formation with the addition of a small quantity of water. The dynamics of water surfactant aggregation in nonpolar solvents is also discussed. Lastly, the performance of the model surfactant as an interfacial tension modifier is studied in detail. The results show that RMs are more easily formed in oil than in scCO2 and that the effectiveness of the surfactant in reducing the interfacial tension lies in its preference to adsorb at interfaces rather than self – association.

Molecular modeling and experimental testing on the comparative performance of macrocyclic and linear zwitterionic surfactants for the emulsified heavy oil recovery

One of the major problems in heavy oil recovery in Mexican carbonate reservoirs is related to the formation of highly stable and viscous water-in-oil emulsions, which impacts on decreasing in hydrocarbon production. This fact is derived from the presence of high amounts of asphaltenes in the oil, as well as from the high concentrations of divalent ions in the formation water. In order to develop a technological solution for this problem, in this work a theoretical/experimental methodology is presented, which allows the development of new surfactants with multifunctional capabilities, such as changes in rock wettability, interfacial tension and emulsion breaking up. The molecular modeling is used to study emulsions formation, as well as the demulsifying capability of two kinds of surfactants: branched geminal zwitterionic liquids and new zwitterionic macrocyclic oxo-aza-crown ethers. Spontaneous-imbibition studies were carried out in order to determine the capacity of these surfactants to increase the oil recovery factor. Both theoretical and experimental parts show that the new macrocyclic surfactants presented a better performance than the branched germinal zwitterionic surfactants, therefore, they constitute a potential technological solution to increase oil recovery factor in the mentioned reservoirs. Their emulsion breaking up capacity, allows to extract oil from the porous media and avoids formation of new emulsions in the extraction process.

Linear anionic surfactant (SDBS) destabilized anammox process through sludge disaggregation and metabolic inhibition

The increase of emerging contaminants, such as surfactants, is one of the major challenges to biological wastewater treatment. However, the potential impact of linear alkylbenzene sulphonates (LAS), a major class of anionic surfactants, on anammox process is unclear. The long-term effects of sodium dodecyl benzene sulfonate (SDBS, as a model LAS) on reactor performance, microbial community and sludge properties were investigated in this study. The presence of 5 mg L−1 SDBS promoted the release of extracellular microbial products from anammox granules and the wash-out of anammox population via effluent. Despite sludge disaggregation, the reactor performance was robust to the exposure of 5 mg L−1 SDBS due to functional redundancy. With the further increase of SDBS to 10 mg L−1, the metabolic activity of anammox biomass and the transcription and post-translation of hydrazine dehydrogenase were significantly decreased. The potential mechanism might be associated with the damage on cell membrane that induced the leakage of intracellular matrix. These results highlight the need to consider the potential risk of LAS to operation of anammox process in biological wastewater treatment plant.