Surfactants

Y. Nakama , in Cosmetic Science and Technology, 2017

15.2 Characteristics and Classification of Surfactants

Surfactants are substances that create self-assembled molecular clusters called micelles in a solution (water or oil phase) and adsorb to the interface between a solution and a dissimilar phase (gases/solids). To bear witness these two physical properties, a surfactant must accept a chemical construction with ii different functional groups with different affinity within the same molecule. Usually the molecules of the substances called surfactants have both an alkyl chain with eight–22 carbons. This chain is chosen a hydrophobic group, which does not show affinity to h2o (they are called hydrophobic groups since surfactants are oftentimes used in water systems, just when used in lipid systems they are chosen lipophilic groups). The surfactant molecules also have a functional group called the hydrophilic group that has affinity to water. This kind of structure with two opposing functions is called an amphiphilic construction.

Surfactants are classified into ionic surfactants and nonionic surfactants. Ionic surfactants are subclassified into anionic surfactants where the hydrophilic group dissociates into anions in aqueous solutions, cationic surfactants that dissociate into cations, and amphoteric surfactants that dissociate into anions and cations ofttimes depending on the pH. Nonionic surfactants are surfactants that exercise not dissociate into ions in aqueous solutions, and they are subclassified depending on the type of their hydrophilic group (Fig. xv.1). Common hydrophilic groups of ionic surfactants are carboxylate (–COO−), sulfate (–OSO3 −), sulfonate (SOthree −), carboxybetaine (–NR2CH2COO−), sulfobetaine (–North(CHthree)2C3HviSO3 −), and 4th ammonium (–RivN+). As an example, a soap molecule has a hydrocarbon chain every bit its lipophilic functional group that has analogousness to lipids (the lipophilic group) and a carboxylate anion as its functional grouping that has affinity to water (the hydrophilic group). In an aqueous solution, the carboxylate anion forms a structure with counterions such as Na+, M+, or Mgii+ (Fig. 15.1). The hydrophilic grouping of nonionic surfactants is unremarkably a polyoxyethylene group, merely there are likewise nonionic surfactants with glyceryl groups or sorbitol groups, and nonionic surfactants with these different hydrophilic groups are likewise used depending on the application.

Effigy 15.ane. Construction and classification of surfactants.

Surfactants are also classified depending on their solubility, such as hydrophilic surfactants that are soluble in water or hydrophobic (lipophilic) surfactants that are soluble in lipids. Ionic surfactants are generally hydrophilic surfactants, but nonionic surfactants tin can exist either hydrophilic or lipophilic, depending on the remainder of the hydrophilic grouping and lipophilic grouping. In other words, the solubility of nonionic surfactants depends on the balance between the hydrophilic grouping's chapters of attracting water and the lipophilic grouping's chapters of attracting oil. Hydrophilic-lipophilic residue (HLB) is an indicator that quantifies this relative balance. HLB was first proposed by Griffin 1 and currently several formulas to calculate HLB accept been reported. 2,3 Since HLB indicates the characteristics of nonionic surfactants, information technology is commonly used equally an indicator for choosing a surfactant for specific applications, such equally emulsifiers or cleansers, which are both mentioned later in this chapter (Fig. 15.two). Notwithstanding, since HLB is but an indicator based on experience, it can exist used every bit a reference to choose a surfactant for an application merely this is not enough in formulation development and that tin lead to many challenges. Knowing the characteristics of surfactants efficiently and quickly is vital in formulation development. In add-on to the HLB, there are ii indicators that subjectively show these characteristics: the deject point for nonionic surfactants and the Krafft point for ionic surfactants.

Effigy 15.2. Index for choosing surfactants.

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Ionic liquid–based surfactants for oil spill remediation

Mansoor Ul Haassan Shah , ... 1000. Moniruzzaman , in Ionic Liquid-Based Technologies for Environmental Sustainability, 2022

16.8 Last remarks and time to come perspectives

ILBS take immense capability to be used for oil spill remediation. The development in this area is based on the designer like properties of ILBS, which make them ideal in oil spill applications. All the same, long concatenation ILs possesses high toxic values. Therefore further studies will be helpful to overcome this problem and to produce more "surround-friendly" ILBS for oil spill application. Although some biobased ILs and fatty acid–based ILs are believed to be less toxic, the dispersion efficiency and their exact toxicity determinations are very crucial for future investigations. Furthermore, worldwide marketplace inquiry has constitute that the demand for ILBS is not available on commercial level, which results in high production costs. Hence, future researchers should focus on synthesizing/designing task-specific low price ILBS to enhance the economic feasibility of oil spill remediations using ILBS. Moreover, the economic factor of ILBS can exist overcome past developing mixed systems, that is, by combining ILBS with other surfactants. The surfactants that are to be combined with ILBS are easy to synthesize and should be sustainable. Therefore more than efforts are required to investigate the dispersion effectiveness as well the environmental effects of the mixed system containing ILs and other surfactants.

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Respiratory Disease Syndrome-Hyaline Membrane Disease

Jeffrey A. Whitsett , in xPharm: The Comprehensive Pharmacology Reference, 2007

Pathophysiology

Surfactant lipids and proteins are synthesized and secreted into the alveolus past type 2 epithelial cells, a procedure that is developmentally regulated and influenced by diverse hormones, including glucocorticoids Jobe and Ikegami (2000). Surfactant production increases with increasing gestational age in the normal neonate. The lack of lung maturity and associated surfactant deficiency cause respiratory distress syndrome (RDS). Pulmonary edema, alveolar capillary leak, pulmonary hemorrhage, and the presence of meconium in the airways can inactivate surfactant. Decreased surfactant activeness results in alveolar collapse, atelectasis, ventilation-perfusion abnormalities, decreased lung compliance, resulting in a decreased ventilation and pulmonary hypertension leading to respiratory failure. Surfactant maintains lung volumes and enhances the clearance of lung liquid. Surfactant replacement decreases the incidence of air leak and mortality that accompany RDS.

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Molecular Construction and Stage Behavior of Surfactants

1000. Miyake , Y. Yamashita , in Cosmetic Science and Technology, 2017

Abstract

Surfactants spontaneously construct a variety of self-organized structures in solvents, which noticeably depend on the chemical structures of surfactants equally well every bit interaction manners with the solvents. A phase diagram is a fundamental tool to requite an interpretation to surfactant backdrop and, in fact, can provide a great deal of authentic information on the structural graphic symbol of the surfactant including its solvation. This chapter introduces the primal concept of stage beliefs in a surfactant system, and thereby reviews the structural effects of surfactant molecules on stage behavior and physicochemical properties using a number of phase diagrams in different surfactant systems.

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Arginine-Based Surfactants: Synthesis, Aggregation Properties, and Applications

Aurora Pinazo , ... Ramon Pons , in Biobased Surfactants (Second Edition), 2019

Abstract

Surfactants are 1 of the most representative chemic products that are consumed in large quantities every twenty-four hours. Attributable to the trend toward greater environmental awareness and protection, there is a pressing need for high-performance surfactants that are biodegradable and biocompatible. Our grouping has developed new biocompatible surfactants derived from amino acids. Amongst them, arginine derivative surfactants constitute a novel class that can be regarded as alternative to conventional cationic surfactants due to their multifunctional properties. The renewable origin of the raw materials used for their synthesis makes them light-green surfactants. In this chapter, the synthesis, adsorption at equilibrium, aggregation, and biological properties of new surfactants derived from arginine amino acrid are described. Our results suggest that arginine surfactants have value as soft preservatives in corrective, food, and pharmaceutical formulations, as well equally being tools for cardinal research.

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Awarding of biosurfactant as a demulsifying and emulsifying agent in the formulation of petrochemical products

Farzad Raeisi , ... Hossein Esmaeili , in Green Sustainable Process for Chemical and Environmental Technology and Science, 2021

i Introduction

Surfactants are an essential or central part of diverse consumer and industrial formulations. Such organic amphiphilic molecules show exclusive authorization to adsorb in aqueous or nonaqueous solution at the self-aggregate, self-gather, interface, or in different phases. Over the past few years, environmental issues accompanied by increased consumer awareness have directed the primary product of environmentally benign surfactant molecules, mostly referred to every bit "dark-green surfactants," "biosurfactants," "natural surfactants," oleo chemical-based surfactants, etc. Such collections of the novel generation of ecologically sensitive surfactant molecules typically derived/developed renewable building blocks—direct or indirectly—may more often than not be named "sustainable surfactants," which are slowly gaining popularity in numerous fields of application. Surfactant molecules, with their amphiphilic character, establish exclusive backdrop of interfaces and self-assembling possessions. Such surface-active materials can be self-assembled in equally polar or nonpolar solvent systems. They are thus used in many industrial and consumer products as wetting agents, dispersants, emulsifiers, and foaming agents [1]. These surfactants were classified into 4 groups, based on their molecular structures, i.e., cationic [2], anionic [3], nonionic [4], and zwitterionic/amphoteric [5] surfactants. Although several robust and diverse molecular systems of the previously mentioned essential varieties take evolved, novel surfactant molecules are oft subclassified into several varieties, including polymeric [6] and gemini [seven] surfactants. Separately from these standard classes, there are numerous specific groups of surfactants too, such as stimuli-responsive [eight] and combination surfactants [9]. It is an exclusive and illustrious physicochemical property comparative to conventional surfactants. Common surfactants are usually fabricated thorough petrochemical feedstock or a hybrid of petrochemical and renewable feedstock. Yet, the pattern presented gives consumers a meliorate understanding and positive view of the surfactants generated using regenerative raw materials (Fig. ane) [10].

Fig. 1

Fig. 1. Representation cycle for surfactant manufacturing [11].

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The Physics of Aerosol*

Jean Berthier , in Micro-Drops and Digital Microfluidics (2d Edition), 2013

3.7.ii From partial wetting to full wetting

All surfactants are not every bit effective in changing droplet wettability. The morphology of the surfactant molecule at the nanoscopic scale is determining. Shen et al. [43] take simulated the event of flexible linear chain surfactants like alkyl bondage, and rigid T-shape surfactants like trisiloxane (Figure 3.80).

Figure iii.80. MD (molecular dynamics) numerical simulations of a droplet spreading on a substrate under the action of T-shape surfactants and flexible linear concatenation surfactants.

 Source: Reprinted with permission from Ref. [43] © 2005, American Chemic Social club.

T-shape surfactants work better than flexible linear surfactants because they facilitate the formation of a liquid motion-picture show. As shown in Figure 3.fourscore, at the bottom left corner, T-shape molecules rearrange between the liquid interface and the solid interface to class a "sandwich" laminating a water picture show.

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Micellar Solutions to Recover Diesel in Sand

Leticia A. Bernardez , Luiz R.P. de Andrade Lima , in The Role of Colloidal Systems in Environmental Protection, 2014

3 Surfactant-enhanced site remediation

Surfactant-enhanced aquifer remediation (SEAR) has been proposed every bit a ways of enhancing the removal of NAPL from contaminated sites. SEAR involves the injection of surfactant solutions to solubilize and mobilize NAPL constituents. The surfactant and contaminants are subsequently extracted through pumping wells. Diverse design approaches may be taken to SEAR, depending on the hydrogeological conditions and the physicochemical properties of the NAPL. The solubilization mechanism, which is at the heart of the SEAR process, is the germination in the groundwater of micelles, in which the molecules of the NAPL are dissolved and and so transported by the groundwater. In the field, SEAR works similarly to pump-and-treat operations except that dilute surfactant solutions are injected into the contaminated aquifer and withdrawn together with the solubilized NAPLs.

The recovery of NAPL so results from enhanced solubility in the micellar solution and/or mobilization of the remainder NAPL because the interfacial tension between the micellar solution and the NAPL is lower than that between water and the NAPL (AATDF, 1999).

Research directed at the evaluation and improvement of SEAR is currently active. Laboratory tests to screen various surfactant systems and to optimize the micellar solutions are being undertaken to make up one's mind whether solubilization or mobilization is nearly appropriate for the site. Several authors have successfully combined surfactants and surfactant and alcohols in a unmarried micellar washing solution for different contaminants. Optimized micellar solutions accept also been shown to recover diesel (Martel and Gélinas, 1996). In improver, column tests to assess the surfactant performance and the label of matrix-fluid interactions have been the focus of extensive research because they are essential prerequisites to field pilot testing.

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The Use of Surfactants to Raise Particle Removal from Surfaces

Michael L. Gratuitous , in Developments in Surface Contagion and Cleaning (Second Edition), 2016

thirteen.4 Summary

Surfactants can enhance particle removal from surfaces by modifying the particle-surface interaction forces. Adsorbed surfactant molecules can alter the van der Waals attractive forcefulness, electrostatic force, hydrophobic forcefulness, every bit well as provide a steric barrier to contact. The effect of surfactants on these forces can result in greatly enhanced particle removal efficiency.

Surfactant adsorption density and structure are important factors in determining removal enhancement performance associated with surfactants. Cleaning is generally most effective above the SAC, which for naturally hydrophilic surfaces allows for bilayer or multilayer level surfactant coverage that provides significant charge repulsion as well every bit a steric barrier. Adsorption below the monolayer level renders naturally hydrophilic substrates hydrophobic, which tends to reduce removal efficiency. In dissimilarity, naturally hydrophobic surfaces are likely to benefit from both sub-monolayer and multilayer coverages of surfactant that occur, respectively, below and above the SAC. Existing adsorption theory and bachelor formulas tin can assistance in the prediction of the SAC, which is an important parameter in predicting the operation of surfactants in particle removal enhancement. Equations are besides available to predict the effectiveness of surfactants in enhancing particle removal.

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Application of Microemulsions in Cleaning Technologies and Environmental Remediation

Edgar J. Acosta , ... David A. Sabatini , in Handbook for Cleaning/Decontamination of Surfaces, 2007

4.1.2. Fundamentals of SEAR Technologies

Surfactants are used in SEAR technologies to increase the contaminant solubility (SEAR solubilization) and/or reduce the oil–h2o interfacial tension to weaken the capillary forces that keep NAPLs trapped in porous media (SEAR mobilization) [ xv–17,143,144,154–156].

SEAR-solubilization techniques are unremarkably used to remove DNAPLs from aquifers. DNAPL-impacted sites can contain a number of components such as TCE, PCE; 1,one,1-trichloroethane, and other chlorinated solvents with densities that range from ane.1 to 1.6 thousand/ml. If these oils are displaced from the porous media as a "plumage of dense oil" they tend to sink deeper into the aquifer, making their removal more difficult. Similar to difficult surface cleaners, the SEAR-solubilization approach seeks to solubilize organic contaminants into the hydrophobic core of micelles, thereby increasing the apparent "aqueous solubility" of the contaminant [16,17,140,141]. The process of oil removal in SEAR-solubilization technology is simple in principle: the surfactant conception is continuously injected into the aquifer, then the surfactant micelles that encounter an NAPL–water interface solubilize the NAPL, and incorporate the solubilized NAPL into the aqueous phase. The surfactant solution loaded with NAPL is continuously extracted from the aquifer, the NAPL is then removed using different separation processes higher up ground, and the surfactant solution is and so re-formulated and re-injected into the aquifer. This semi-airtight continuous loop is monitored by measuring concentration of NAPL in the extracted surfactant solution to evaluate the need to change flow configuration or stop the surfactant flush. After the surfactant flush is completed, water is flushed through the system to remove whatever residuum surfactant from the aquifer and re-equilibrate the organisation. The concentration of NAPL in the extracted h2o is closely monitored to decide thereduction of this concentration with respect to the initial value. The success of a remediation applied science is evaluated in terms of the reduction of the aqueous NAPL concentration and the fraction of total NAPL removed (this is called source reduction). Likewise, the mass rest of the surfactant is an important parameter to determine the amount of surfactant retained in the aquifer. SEAR solubilization uses relatively large quantities of surfactants, typically the surfactant concentration ranges between 2 and eight% of anionic surfactants (e.thousand. sodium dihexyl sulfosuccinate), and/or nonionic surfactants (due east.thou. alkyl polyethylene glycols), and medium-chain alcohols (isopropanol, pentanol, etc.) [143,144].

SEAR mobilization is a technology that has been increasingly used for the removal of LNAPLs from the subsurface. In this approach, a low surfactant concentration (near CμC values) is required to reduce the oil–water interfacial tension to values near 0.001 mN/m, which in plough reduces the capillary forces, and the work of adhesion and cohesion of the oil. Under these atmospheric condition, the oil is easily displaced from the porous media by viscous forces arising from the flow of the surfactant conception. This oil mobilization produces oil lenses on top of the aquifer that can be hands nerveless using advisable menstruum configurations [157,158].

It is necessary to clarify that in nigh cases the oil is removed past a combination of mobilization and solubilization mechanisms; this is specially true in some of the first field demonstrations of the SEAR technology when it was not clear how to separate solubilization vs the mobilization effects.

Figure 7.xi shows a schematic of a typical SEAR remediation facility. First, the surfactant solution is contained in tank A, from here some salt, alcohol, water, or whatever other additive could exist added if needed using the stirred tank F. From tank F, the solution is pumped into the injection well(southward) B. The surfactant solution flows through the aquifer solubilizing and/or mobilizing the contaminant (dotted surface area) and the NAPL-laden surfactant solution is extracted from the aquifer through the extraction well(s) C. The extracted solution is then collected in tank D for equalization purposes and to let any complimentary phase of oil separate from the aqueous surfactant solution. The surfactant solution is so pumped through a packed belfry E, where the organic contaminant is air-stripped from the liquid solution. The aqueous surfactant solution may be full-bodied using ultrafiltration membranes (not shown in the schematic) and the surfactant solution is kept in holding tank A ready for re-injection [16,17,156,159]. The reuse of concentrated surfactant solutions is the central to reduce the uppercase price associated with this technology and maintain its toll effectiveness [fifteen].

Figure 7.11. Schematic of a SEAR remediation process.

 Adapted from Childs et al, [159]

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