# Surfactant
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{{Short description|Substance that lowers surface tension}}
{{Use dmy dates|cs1-dates=ll|date=July 2025}}
[[File:A lipid micelle.png|thumb|[Schematic](/source/Schematic) diagram of a [micelle](/source/micelle) of oil in aqueous suspension, such as might occur in an [emulsion](/source/emulsion) of oil in water. In this example, the surfactant molecules' oil-soluble tails project into the oil (blue), while the water-soluble ends remain in contact with the water phase (red).]]
A '''surfactant''' is a [chemical compound](/source/chemical_compound) that decreases the [surface tension](/source/surface_tension) or interfacial tension between two [liquid](/source/liquid)s, a liquid and a [gas](/source/gas), or a liquid and a [solid](/source/solid). The word ''surfactant'' is a [blend](/source/Blend_word) of "surface-active agent",[{{Cite book |url= https://books.google.com/books?id=1rCdNIzB78AC |title=Surfactants and Interfacial Phenomena |last1=Rosen |first1=M. J. |last2=Kunjappu |first2=J. T. |publisher=John Wiley & Sons |date=2012 |isbn=978-1-118-22902-6 |edition=4th |location=Hoboken, New Jersey |page=1 |quote=A surfactant (a contraction of '''''surf'''ace-'''act'''ive '''a'''ge'''nt''''') is a substance that, when present at low concentration in a system, has the property of adsorbing onto the surfaces or interfaces of the system and of altering to a marked degree the surface or interfacial free energies of those surfaces (or interfaces). |archive-url= https://web.archive.org/web/20170108051750/https://books.google.com/books?id=1rCdNIzB78AC&printsec=frontcover |archive-date=8 January 2017 |url-status=live }}] coined in 1950.[{{oed|surfactant}} – "A new word, Surfactants, has been coined by Antara Products, General Aniline & Film Corporation, and has been presented to the chemical industry to cover all materials that have surface activity, including wetting agents, dispersants, emulsifiers, detergents and foaming agents."] As they consist of a water-repellent and a water-attracting part, they are [emulsifier](/source/emulsifier)s, enabling water and oil to mix. They can also form foam, and facilitate the detachment of dirt.
Surfactants are among the most widespread and commercially important chemicals. Private households as well as many industries use them in large quantities as [detergents and cleaning agent](/source/Detergent)s, but also as emulsifiers, [wetting](/source/wetting) agents, [foaming agent](/source/foaming_agent)s, [antistatic](/source/antistatic) additives, and [dispersant](/source/dispersant)s.
Surfactants occur naturally in traditional plant-based detergents, e.g. [horse chestnuts](/source/horse_chestnuts) or [soap nuts](/source/soap_nuts); they can also be found in the secretions of some caterpillars. Some of the most commonly used anionic surfactants, linear alkylbenzene sulfates (LAS), are produced from [petroleum products](/source/petroleum_products). However, surfactants are increasingly produced in whole or in part from renewable [biomass](/source/biomass), like sugar, fatty alcohol from vegetable oils, by-products of biofuel production, and other biogenic material.[{{Cite web |title=Biobased Surfactants Market Report: Market Analysis |url= https://ceresana.com/en/produkt/biobased-surfactants-market-report-world |access-date=5 January 2024 |website=Ceresana Market Research}}]
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==Classification==
Surfactants are compounds with [hydrophilic](/source/hydrophilic) "heads" and [hydrophobic](/source/hydrophobic) "tails." The "heads" of surfactants are polar and may or may not carry an electrical charge. The "tails" of most surfactants are fairly similar, often consisting of a [hydrocarbon](/source/hydrocarbon) chain (linear or branched) and may comprise [aromatic units](/source/Aromatic_compound). Most commonly, surfactants are classified according to the polarity of their head group: A ''non-ionic'' surfactant has no charged groups in its head. The head of an ionic surfactant carries a net positive, or negative, charge. If the charge is negative, the surfactant is more specifically called ''anionic''; if the charge is positive, it is called ''cationic''. If a surfactant contains a head with two oppositely charged groups, it is termed [''zwitterionic''](/source/Zwitterion), or ''amphoteric''.
thumb|upright=1.2|Surfactant classification according to the composition of their head: non-ionic, anionic, cationic, amphoteric.
However, surfactants may also be classified based on chemical structure or based on their properties / their application.
=== Classification according to charge / polarity ===
==== Anionic: sulfate, sulfonate, and phosphate, carboxylate derivatives ====
[Anion](/source/Anion)ic surfactants contain anionic functional groups at their head, such as [sulfate](/source/organosulfate), [sulfonate](/source/sulfonate), [phosphate](/source/phosphate), and [carboxylate](/source/carboxylic_acid)s.
Prominent alkyl sulfates include [ammonium lauryl sulfate](/source/ammonium_lauryl_sulfate), [sodium lauryl sulfate](/source/sodium_lauryl_sulfate) (sodium dodecyl sulfate, SLS, or SDS), and the related alkyl-ether sulfates [sodium laureth sulfate](/source/sodium_laureth_sulfate) (sodium lauryl ether sulfate or SLES), and [sodium myreth sulfate](/source/sodium_myreth_sulfate).
thumb|alt=Sodium dodecylbenzenesulfonate|4-(5-Dodecyl) benzenesulfonate, a linear alkylbenzene sulfonate, one of the most common surfactants
Others include:
* [Alkylbenzene sulfonate](/source/Alkylbenzene_sulfonate)s
* [Docusate](/source/Docusate) (dioctyl sodium sulfosuccinate)
* [Perfluorooctanesulfonate](/source/perfluorooctanesulfonic_acid) (PFOS)
* [Perfluorobutanesulfonate](/source/Perfluorobutanesulfonic_acid)
* Alkyl-aryl ether phosphates
* Alkyl ether phosphates
[[File:sodium stearate.svg|thumb|[Sodium stearate](/source/Sodium_stearate), the most common component of most soap, which comprises about 50% of commercial surfactants]]
Carboxylates are the most common surfactants and comprise the carboxylate salts ([soap](/source/soap)s), such as [sodium stearate](/source/sodium_stearate). More specialized species include [sodium lauroyl sarcosinate](/source/sodium_lauroyl_sarcosinate) and carboxylate-based fluorosurfactants such as [perfluorononanoate](/source/perfluorononanoate), [perfluorooctanoate](/source/perfluorooctanoate) (PFOA or PFO).
==== Cationic head groups ====
Cationic surfactants are extensively described in this review.[{{Cite journal |last1=Gonçalves |first1=Rui A. |last2=Holmberg |first2=Krister |last3=Lindman |first3=Björn |date=1 April 2023 |title=Cationic surfactants: A review |url= |journal=Journal of Molecular Liquids |volume=375 |article-number=121335 |doi=10.1016/j.molliq.2023.121335 |issn=0167-7322}}]
pH-dependent primary, secondary, or tertiary [amine](/source/amine)s; primary and secondary amines become positively charged at pH < 10:[{{Cite web |title=Bordwell pKa Table (Acidity in DMSO) |url= http://www.chem.wisc.edu/areas/reich/pkatable/index.htm |date=2012 |first=Hans J. |last=Reich |publisher=University of Wisconsin |access-date=2 April 2013 |archive-date=27 December 2012 |archive-url= https://web.archive.org/web/20121227045833/http://www.chem.wisc.edu/areas/reich/pkatable/index.htm |url-status=live}}] [octenidine dihydrochloride](/source/octenidine_dihydrochloride).
Permanently charged [quaternary ammonium salts](/source/quaternary_ammonium_salts): [cetrimonium bromide](/source/cetrimonium_bromide) (CTAB), [cetylpyridinium chloride](/source/cetylpyridinium_chloride) (CPC), [benzalkonium chloride](/source/benzalkonium_chloride) (BAC), [benzethonium chloride](/source/benzethonium_chloride) (BZT), [dimethyldioctadecylammonium chloride](/source/dimethyldioctadecylammonium_chloride), and [dioctadecyldimethylammonium bromide](/source/DODAB) (DODAB).
==== Zwitterionic surfactants ====
[Zwitterion](/source/Zwitterion)ic ([ampholytic](/source/ampholytic)) surfactants have both cationic and anionic centers attached to the same molecule. The cationic part is based on primary, secondary, or tertiary [amine](/source/amine)s or quaternary ammonium cations. The anionic part can be more variable and include sulfonates, as in the [sultaines](/source/hydroxysultaine) [CHAPS](/source/CHAPS_detergent) (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) and [cocamidopropyl hydroxysultaine](/source/cocamidopropyl_hydroxysultaine). [Betaine](/source/Betaine)s such as [cocamidopropyl betaine](/source/cocamidopropyl_betaine) have a carboxylate with the ammonium. The most common biological zwitterionic surfactants have a phosphate anion with an amine or ammonium, such as the [phospholipids](/source/phospholipids) [phosphatidylserine](/source/phosphatidylcholine), [phosphatidylethanolamine](/source/phosphatidylethanolamine), [phosphatidylcholine](/source/phosphatidylcholine), and [sphingomyelin](/source/sphingomyelin)s.
[Lauryldimethylamine oxide](/source/Lauryldimethylamine_oxide) and [myristamine oxide](/source/myristamine_oxide) are two commonly used zwitterionic surfactants of the tertiary [amine oxide](/source/amine_oxide)s structural type.
==== Non-ionic ====
Non-ionic surfactants have covalently bonded oxygen-containing hydrophilic groups, which are bonded to hydrophobic parent structures. The water-solubility of the oxygen groups is the result of [hydrogen bonding](/source/hydrogen_bonding). Hydrogen bonding decreases with increasing temperature, and the water solubility of non-ionic surfactants therefore decreases with increasing temperature.
Non-ionic surfactants are less sensitive to water hardness than anionic surfactants, and they foam less strongly. The differences between the individual types of non-ionic surfactants are slight, and the choice is primarily governed having regard to the costs of special properties (e.g., effectiveness and efficiency, toxicity, dermatological compatibility, [biodegradability](/source/biodegradability)) or permission for use in food.[{{Cite journal |last=Chiappisi |first=Leonardo |date=December 2017 |title=Polyoxyethylene alkyl ether carboxylic acids: An overview of a neglected class of surfactants with multiresponsive properties |journal=Advances in Colloid and Interface Science |volume=250 |pages=79–94 |doi=10.1016/j.cis.2017.10.001 |pmid=29056232}}]
====== Special ethoxylated fatty esters and oils ======
====== Ethoxylated amines and/or fatty acid amides ======
* [Polyethoxylated tallow amine](/source/Polyethoxylated_tallow_amine)
* [Cocamide monoethanolamine](/source/Cocamide_monoethanolamine)
* [Cocamide diethanolamine](/source/Cocamide_diethanolamine)
===== Fatty acid esters of polyhydroxy compounds =====
====== Fatty acid esters of glycerol ======
* [Glycerol monostearate](/source/Glycerol_monostearate)
* [Glycerol monolaurate](/source/Glycerol_monolaurate)
====== Fatty acid esters of sorbitol ======
[Spans](/source/Sorbitan):
* [Sorbitan monolaurate](/source/Sorbitan_monolaurate)
* [Sorbitan monostearate](/source/Sorbitan_monostearate)
* [Sorbitan tristearate](/source/Sorbitan_tristearate)
[Tweens](/source/Polysorbate):
* [Tween 20](/source/Tween_20)
* [Tween 40](/source/Tween_40)
* [Tween 60](/source/Tween_60)
* [Tween 80](/source/Tween_80)
====== Fatty acid esters of sucrose ======
===== Alkyl polyglucosides =====
{{main|Alkyl polyglycoside}}[Alkyl polyglycosides](/source/Alkyl_polyglycoside) (APGs) are a class of non-ionic surfactants made from a [sugar](/source/sugar) (like [glucose](/source/glucose)) and a [fatty alcohol](/source/fatty_alcohol). They are produced from renewable resources, possess a high biodegradability and mildness. For these reasons, they are widely used in detergents, [cosmetics](/source/cosmetics), and other applications.[{{cite book |title=Alkyl Polyglycosides |publisher=Wiley-VCH |date=2008 |isbn=978-3-527-61468-4 |editor1-last=Hill |editor1-first=Karlheinz |editor2-last=von Rybinski |editor2-first=Wolfgang |editor3-last=Stoll |editor3-first=Gerhard}}][{{Cite journal |last1=von Rybinski |first1=Wolfgang |last2=Hill |first2=Karlheinz |date=1998 |title=Alkyl Polyglycosides—Properties and Applications of a new Class of Surfactants |journal=Angewandte Chemie |edition=International |volume=37 |issue=10 |pages=1328–1345 |doi=10.1002/(SICI)1521-3773(19980605)37:10<1328::AID-ANIE1328>3.0.CO;2-9 |pmid=29710912 |issn=1521-3773}}]
* [Decyl glucoside](/source/Decyl_glucoside)
* [Lauryl glucoside](/source/Lauryl_glucoside)
* [Octyl glucoside](/source/Octyl_glucoside)
=== Classification according to chemical structure ===
Most surfactants comprise "tails" based on saturated or unsaturated hydrocarbons. [Fluorosurfactant](/source/Fluorosurfactant)s have [fluorocarbon](/source/fluorocarbon) chains. [Siloxane surfactant](/source/Siloxane_surfactant)s have [siloxane](/source/siloxane) chains.
[[File:Gemini surfactant.png|thumb|Gemini amino acid-based surfactant (based on [cysteine](/source/cysteine))]]
Surfactant molecules have either one tail or two; those with two tails are said to be ''double-chained''.[{{cite web |title=Surfactant {{!}} Defination, Classification, Properties & Uses |url= https://www.esteem-india.com/What-makes-a-surfactant.php |website=www.esteem-india.com}}]
[Amino acid-based surfactant](/source/Amino_acid-based_surfactant)s are surfactants derived from an [amino acid](/source/amino_acid). Their properties vary and can be either anionic, cationic, or zwitterionic, depending on the amino acid used and which part of the amino acid is condensed with the alkyl/aryl chain.[{{cite journal |last1=Bordes |first1=Romain |last2=Holmberg |first2=Krister |date=28 March 2015 |title=Amino acid-based surfactants – do they deserve more attention? |journal=[Advances in Colloid and Interface Science](/source/Advances_in_Colloid_and_Interface_Science) |volume=222 |pages=79–91 |doi=10.1016/j.cis.2014.10.013 |pmid=25846628}}]
[Gemini surfactant](/source/Gemini_surfactant)s consist of two surfactant molecules linked together at or near their head groups. Compared to monomeric surfactants, they have much lower [critical micelle concentration](/source/critical_micelle_concentration)s.[{{cite web |access-date=5 July 2025 |title=Emulsions: making oil and water mix – AOCS |url= https://www.aocs.org/resource/emulsions-making-oil-and-water-mix/}}]
|-
|'''[Solubilizers](/source/Solubilizer)'''
|Help dissolve poorly soluble substances
|Perfume in water-based sprays
|-
|'''[Conditioners](/source/Conditioner_(chemistry))'''
|Deposit active ingredients on hair/skin
|Hair conditioners (often cationic surfactants)
|}
==Composition and structure==
File:MicelleV2.svg|Aggregate of anionic surfactants in water ([spherical micelle](/source/Micelle))
File:TensidOelV2.svg|Surfactant-oil droplets in water. The oil is dispersed in water and the surfactant is at the oil-water interface.
File:Oberflächenschicht Tensidlösung.svg|Surfactant molecules at the water surface (= air water interface)
File:TensidUndFeststoffe.svg|Solid and hydrophobic particles (e. g. dirt) are removed from a solid (e. g. a fabric) with the aid of a surfactant (e. g. during washing in the washing machine)
File:Schaumbläschen.svg|Foam bubbles: a "[soap bubble](/source/soap_bubble)"
[[Image:Micelle scheme-en.svg|thumb|upright=1.35|[Schematic](/source/Schematic) diagram of a [micelle](/source/micelle) – the [lipophilic](/source/lipophilic) tails of the surfactant ions remain inside the oil because they interact more strongly with oil than with water. The [polar](/source/Chemical_polarity) "heads" of the surfactant molecules coating the micelle interact more strongly with water, so they form a [hydrophilic](/source/hydrophilic) outer layer that forms a barrier between micelles. This inhibits the oil droplets, the hydrophobic cores of micelles, from merging into fewer, larger droplets ("emulsion breaking") of the micelle. The compounds that coat a micelle are typically [amphiphilic](/source/amphiphilic) in nature, meaning that micelles may be stable either as droplets of [aprotic](/source/aprotic) solvents such as oil in water, or as protic solvents such as water in oil. When the droplet is aprotic it is sometimes{{when|date= February 2019}} known as a reverse micelle.]]
Surfactants are (usually [organic](/source/Organic_compound)) compounds that are [amphiphilic](/source/amphiphilic), which means that this molecule each contains a [hydrophilic](/source/hydrophilic) "water-seeking" group (the ''head''), and a [hydrophobic](/source/hydrophobic) "water-avoiding" group (the ''tail'').[{{cite web |title=Bubbles, Bubbles, Everywhere, But Not a Drop to Drink |url= http://www.samuelfurse.com/2011/11/bubbles-bubbles-everywhere-but-not-a-drop-to-drink/ |work=The Lipid Chronicles |access-date=1 August 2012 |url-status=live |archive-url= https://web.archive.org/web/20120426082602/http://www.samuelfurse.com/2011/11/bubbles-bubbles-everywhere-but-not-a-drop-to-drink/ |archive-date=26 April 2012 |date=11 November 2011}}] As a result, a surfactant contains both a water-soluble component and a water-insoluble component. Surfactants diffuse in water and get [adsorb](/source/adsorb)ed at [interfaces](/source/Interface_(chemistry)) between air and water, or at the interface between oil and water in the case where water is mixed with oil. The water-insoluble hydrophobic group may extend out of the bulk water phase into a non-water phase such as air or oil phase, while the water-soluble head group remains bound in the water phase.
The hydrophobic tail may be either [lipophilic](/source/lipophilic) ("oil-seeking") or [lipophobic](/source/lipophobic) ("oil-avoiding") depending on its chemistry. [Hydrocarbon](/source/Hydrocarbon) groups are usually lipophilic, for use in soaps and detergents, while [fluorocarbon](/source/fluorocarbon) groups are lipophobic, for use in [repelling stains](/source/Stain_repellent) or reducing surface tension.
World production of surfactants is estimated at 15 million tons per year, of which about half are [soap](/source/soap)s. Other surfactants produced on a particularly large scale are linear [alkylbenzene sulfonates](/source/alkylbenzene_sulfonates) (1.7 million tons/y), [lignin sulfonate](/source/lignin_sulfonate)s (600,000 tons/y), [fatty alcohol](/source/fatty_alcohol) [ethoxylate](/source/ethoxylate)s (700,000 tons/y), and [alkylphenol](/source/alkylphenol) [ethoxylate](/source/ethoxylate)s (500,000 tons/y).[Kurt Kosswig "Surfactants" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, 2005, Weinheim. {{doi|10.1002/14356007.a25_747}}]
===Structure of surfactant phases in water===
{{main|Wetting solution}}
In the bulk aqueous phase, surfactants form aggregates, such as [micelles](/source/micelles), where the hydrophobic tails form the core of the aggregate and the hydrophilic heads are in contact with the surrounding liquid. Other types of aggregates can also be formed, such as spherical or cylindrical micelles or [lipid bilayer](/source/lipid_bilayer)s. The shape of the aggregates depends on the chemical structure of the surfactants, namely the balance in size between the hydrophilic head and hydrophobic tail. A measure of this is the [hydrophilic-lipophilic balance](/source/hydrophilic-lipophilic_balance) (HLB). Surfactants reduce the [surface tension](/source/surface_tension) of water by [adsorbing](/source/Adsorption) at the liquid-air interface. The relation that links the surface tension and the surface excess is known as the [Gibbs isotherm](/source/Gibbs_isotherm).
===Dynamics of surfactants at interfaces===
The dynamics of surfactant adsorption is of great importance for practical applications such as in foaming, emulsifying or coating processes, where bubbles or drops are rapidly generated and need to be stabilized. The dynamics of absorption depend on the [diffusion coefficient](/source/diffusion_coefficient) of the surfactant. As the interface is created, the adsorption is limited by the diffusion of the surfactant to the interface. In some cases, there can exist an energetic barrier to adsorption or desorption of the surfactant. If such a barrier limits the adsorption rate, the dynamics are said to be ‘kinetically limited'. Such energy barriers can be due to [steric](/source/steric) or [electrostatic repulsion](/source/electrostatic_repulsion)s.
The surface rheology of surfactant layers, including the elasticity and viscosity of the layer, play an important role in the stability of foams and emulsions.
===Characterization of interfaces and surfactant layers===
Interfacial and surface tension can be characterized by classical methods such as the
-pendant or [spinning drop method](/source/spinning_drop_method).
Dynamic surface tensions, i.e. surface tension as a function of time, can be obtained by the [maximum bubble pressure apparatus](/source/Maximum_bubble_pressure_method)
The structure of surfactant layers can be studied by [ellipsometry](/source/ellipsometry) or [X-ray reflectivity](/source/X-ray_reflectivity).
Surface rheology can be characterized by the oscillating drop method or shear surface rheometers such as double-cone, double-ring or magnetic rod shear surface rheometer.
==Applications==
Surfactants are widely used due to their ability to modify surface and interfacial properties, making them relevant in processes involving the interaction of hydrophobic and hydrophilic substances. Their amphiphilic nature—containing both hydrophilic and hydrophobic parts—enables them to bridge these otherwise immiscible components, thereby facilitating mixing and enhancing the efficiency of various physical and chemical transformations. This makes surfactants useful in numerous fields where control over interfacial interactions is relevant.
Surfactants play an important role as cleaning, [wetting](/source/wetting), [dispersing](/source/Dispersant), [emulsifying](/source/Emulsifier), [foaming](/source/foaming_agent) and [anti-foaming](/source/Defoamer) agents in many practical applications and products, including [detergent](/source/detergent)s, [fabric softener](/source/fabric_softener)s, [motor oil](/source/motor_oil)s, [emulsion](/source/emulsion)s, [soap](/source/soap)s, [paint](/source/paint)s, [adhesive](/source/adhesive)s, [ink](/source/ink)s, [anti-fog](/source/anti-fog)s, [ski wax](/source/ski_wax)es, snowboard wax, in flotation, washing and enzymatic processes, and [laxative](/source/laxative)s.
=== Food industry ===
Certain surfactants are used as [emulsifiers](/source/emulsifiers) or [foaming agents](/source/Foaming_agent) in food. Examples can be found in the [List of food additives](/source/List_of_food_additives).
The alkalization ([saponification](/source/saponification)) of cocoa fat in drinking cocoa powder serves to reduce the surface tension of the milk and to enable faster wetting or suspension of the semi-fat cocoa powder.
=== Personal care and homecare ===
Surfactants are used in [detergents](/source/Detergent), [washing-up liquids](/source/Dishwashing_liquid), [shampoos](/source/Shampoo), [shower gels](/source/Shower_gel), and similar products to increase the “solubility” of fat and dirt particles that adhere to laundry or the body in water.
[Fabric softeners](/source/Fabric_softener) can consist of cationic surfactants that prevent laundry from becoming stiff when dry.
=== Pharmaceuticals and cosmetics ===
[Emulsifiers](/source/Emulsifiers) are essential for producing [water-in-oil emulsions](/source/Water-in-oil_emulsion), e.g. for [skin creams](/source/Skin_Cream_(cosmetic)). They are also necessary for a wide range of suspensions to maintain liquid drug formulations.
=== Plant protection products ===
Plant protection products contain surfactants to improve wetting (spreading) on plants. The most common wetting agent is ethoxylated tallow amine. Trisiloxanes or polyoxyethylated fatty alcohols are also used.[[http://www.tstip.de/downs/Syngenta/ApplikationGrundlagen-Syngenta.pdf Syngenta: Applikationstechnik Ackerbau – Additive – Wichtige Additive.] (PDF; 0,9 MB) tstip.de, S. 11.] Agrochemical formulations that use surfactants include [herbicide](/source/herbicide)s (some), [insecticide](/source/insecticide)s, [biocide](/source/biocide)s (sanitizers).[{{cite journal |last1=Paria |first1=Santanu |date=2008 |title=Surfactant-enhanced remediation of organic contaminated soil and water |journal=Advances in Colloid and Interface Science |volume=138 |issue=1 |pages=24–58 |doi=10.1016/j.cis.2007.11.001 |pmid=18154747}}]
=== Medicine ===
Surfactants act to cause the displacement of air from the matrix of cotton pads and bandages so that medicinal solutions can be absorbed for application to various body areas. They also act to displace dirt and debris by the use of detergents in the washing of wounds[{{Cite journal |last1=Percival |first1=S.l. |last2=Mayer |first2=D. |last3=Malone |first3=M. |last4=Swanson |first4=T |last5=Gibson |first5=D. |last6=Schultz |first6=G. |date=2 November 2017 |title=Surfactants and their role in wound cleansing and biofilm management |journal=Journal of Wound Care |volume=26 |issue=11 |pages=680–690 |doi=10.12968/jowc.2017.26.11.680 |issn=0969-0700 |pmid=29131752}}] and via the application of medicinal lotions and sprays to surface of skin and mucous membranes.[{{Cite journal |last1=Mc Callion |first1=O. N. M. |last2=Taylor |first2=K. M. G. |last3=Thomas |first3=M. |last4=Taylor |first4=A. J. |date=8 March 1996 |title=The influence of surface tension on aerosols produced by medical nebulisers |journal=International Journal of Pharmaceutics |volume=129 |issue=1 |pages=123–136 |doi=10.1016/0378-5173(95)04279-2 |issn=0378-5173}}] Surfactants enhance remediation via soil washing, bioremediation, and phytoremediation.[{{Cite journal |last1=Bolan |first1=Shiv |last2=Padhye |first2=Lokesh P. |last3=Mulligan |first3=Catherine N. |last4=Alonso |first4=Emilio Ritore |last5=Saint-Fort |first5=Roger |last6=Jasemizad |first6=Tahereh |last7=Wang |first7=Chensi |last8=Zhang |first8=Tao |last9=Rinklebe |first9=Jörg |last10=Wang |first10=Hailong |last11=Siddique |first11=Kadambot H. M. |last12=Kirkham |first12=M. B. |last13=Bolan |first13=Nanthi |date=5 February 2023 |title=Surfactant-enhanced mobilization of persistent organic pollutants: Potential for soil and sediment remediation and unintended consequences |url= https://www.sciencedirect.com/science/article/pii/S0304389422019835 |journal=Journal of Hazardous Materials |volume=443 |issue=Pt A |article-number=130189 |bibcode=2023JHzM..44330189B |doi=10.1016/j.jhazmat.2022.130189 |issn=0304-3894 |pmid=36265382 |url-access=subscription}}]
Many [spermicide](/source/spermicide)s contain surfactants (such as [nonoxynol-9](/source/nonoxynol-9)).
=== Biochemistry ===
In solution, detergents help solubilize a variety of chemical species by dissociating aggregates and unfolding proteins. Popular surfactants in the biochemistry laboratory are [sodium lauryl sulfate](/source/sodium_lauryl_sulfate) (SDS) and [cetyl trimethylammonium bromide](/source/cetyl_trimethylammonium_bromide) (CTAB). Detergents are key reagents to [extract](/source/Liquid-liquid_extraction) protein by lysis of the cells and tissues: they disorganize the membrane's [lipid bilayer](/source/lipid_bilayer) (SDS, [Triton X-100](/source/Triton_X-100), [X-114](/source/Triton_X-114), [CHAPS](/source/CHAPS_detergent), [DOC](/source/Cholate), and [NP-40](/source/NP-40)), and solubilize proteins. Milder detergents such as [octyl thioglucoside](/source/octyl_thioglucoside), [octyl glucoside](/source/octyl_glucoside) or [dodecyl maltoside](/source/maltosides) are used to solubilize membrane proteins such as [enzymes](/source/enzymes) and [receptors](/source/Receptor_(biochemistry)) without [denaturing](/source/Denaturation_(biochemistry)) them. Non-solubilized material is harvested by centrifugation or other means. For [electrophoresis](/source/electrophoresis), for example, proteins are classically treated with SDS to denature the native [tertiary and quaternary structures](/source/protein_structure), allowing the separation of proteins according to their [molecular weight](/source/molecular_weight).
Detergents have also been used to decellularise organs. This process maintains a matrix of proteins that preserves the structure of the organ and often the microvascular network. The process has been successfully used to prepare organs such as the liver and heart for transplant in rats.[{{cite web |last=Wein |first=Harrison |date=28 June 2010 |title=Progress Toward an Artificial Liver Transplant – NIH Research Matters |url= http://www.nih.gov/researchmatters/june2010/06282010liver.htm |url-status=dead |archive-url= https://archive.today/20120805083144/http://www.nih.gov/researchmatters/june2010/06282010liver.htm |archive-date=5 August 2012 |publisher=National Institutes of Health (NIH) }}] [Pulmonary surfactant](/source/Pulmonary_surfactant)s are also naturally secreted by type II cells of the lung [alveoli](/source/Pulmonary_alveolus) in [mammals](/source/mammals).
=== Technology ===
==== Antistatic agents ====
Ionic surfactants also function as external antistatic agents to prevent electrostatic charging of plastic surfaces (ESD protection). Both anionic and cationic surfactants are used for this purpose[9].
==== Textile finishing ====
Perfluorinated surfactants, such as fluorotelomer alcohols (FTOH), are used as coating agents for textiles, carpets, and construction products to impart or enhance water and grease repellency. As members of the PFC group, however, they are subject to criticism because they are persistent and practically non-degradable in nature.
==== Cooling lubricants ====
Surfactants are employed in water-mixed cooling lubricants (water-in-oil emulsions) to provide effective cooling and lubrication during metal cutting operations.
==== Printer ink ====
Surfactants regulate the consistency of ink in inkjet printers. An insufficient amount of surfactants results in clumping of the color pigments, whereas an excessive amount renders the ink overly fluid during printing.
==== Paper recycling ====
In [paper recycling](/source/paper_recycling), surfactants facilitate the detachment of ink particles from paper fibers ([deinking](/source/deinking)) and assist in transporting the ink to the surface.
==== Oil and mining industry ====
Alkali surfactant polymers are used to mobilize oil in [oil well](/source/oil_well)s. Surfactants also play a key role in [froth flotation](/source/froth_flotation) processes for separating copper and other minerals from [ores](/source/Ore).
=== Fire fighting ===
Surfactants are used in [firefighting](/source/firefighting) (to make "wet water" that more quickly soaks into flammable materials[[https://www.techtimes.com/articles/293401/20230704/wet-water-outperforms-regular-firefighting-fire-wetting-agents.htm Better Than Water? How Wet Water Outperforms Regular Water in Firefighting]][[https://www.hngn.com/articles/250072/20230704/firefighters-turn-to-wet-water-to-fight-larger-more-complex-fires.htm Firefighters Turn to "Wet Water" to Fight Larger, More Complex Fires]]) and pipelines (liquid drag reducing agents).
"Wet water" provides the advantage of allowing the extinguishing water to penetrate burning materials such as wood or fabric more effectively, thereby enhancing its cooling capacity. Additionally, extinguishing water mixed with surface-active agents can be sprayed over greater distances at the same pumping capacity due to their flow-improving properties. Special foaming agents ([Aqueous Film Forming Foam](/source/Aqueous_Film_Forming_Foam), AFFF) for combating liquid fires contain perfluorinated surfactants that form a gas-tight liquid film between the burning material and the foam. This simultaneously imparts superior sliding properties to the foam blanket, thereby enabling the effective extinguishment of larger liquid fires.
=== Surfactants in droplet-based microfluidics ===
Surfactants play an important role in [droplet-based microfluidics](/source/droplet-based_microfluidics) in the stabilization of the droplets, and the prevention of the fusion of droplets during incubation.[{{Cite journal |last=Baret |first=Jean-Christophe |date=10 January 2012 |title=Surfactants in droplet-based microfluidics |url= https://pubs.rsc.org/en/content/articlelanding/2012/lc/c1lc20582j |journal=Lab on a Chip |volume=12 |issue=3 |pages=422–433 |doi=10.1039/C1LC20582J |pmid=22011791 |issn=1473-0189 |access-date=18 April 2020 |archive-date=14 February 2020 |archive-url= https://web.archive.org/web/20200214151429/https://pubs.rsc.org/en/content/articlelanding/2012/LC/C1LC20582J |url-status=live}}]
===Human body and nature===
{{further|Pulmonary surfactant}}
[[Image:1-Oleoyl-2-almitoyl-phosphatidylcholine Structural Formulae V.1.png|thumb|300px|[Phosphatidylcholine](/source/Phosphatidylcholine), found in lecithin, is a pervasive biological surfactant. Shown in {{color|#800000|red}} – [choline](/source/choline) and [phosphate](/source/phosphate) group; {{color|#000000|black}} – [glycerol](/source/glycerol); {{color|#008000|green}} – [monounsaturated fatty acid](/source/monounsaturated_fatty_acid); {{color|#000080|blue}} – [saturated fatty acid](/source/saturated_fatty_acid).]]
The human body produces diverse surfactants. [Pulmonary surfactant](/source/Pulmonary_surfactant) is produced in the [lung](/source/lung)s in order to facilitate breathing by increasing [total lung capacity](/source/total_lung_capacity), and [lung compliance](/source/lung_compliance). In [respiratory distress syndrome](/source/Respiratory_distress_syndrome%2C_adult) or RDS, [surfactant replacement](/source/Pulmonary_surfactant_(medication)) therapy helps patients have normal respiration by using pharmaceutical forms of the surfactants. One example of a pharmaceutical pulmonary surfactant is Survanta ([beractant](/source/beractant)) or its generic form Beraksurf, produced by [Abbvie](/source/Abbvie) and [Tekzima](/source/Tekzima) respectively. [Bile salts](/source/Bile_salts), a surfactant produced in the liver, play an important role in digestion.[{{cite journal |doi=10.1016/j.cis.2010.12.002 |pmid=21236400 |title=The role of bile salts in digestion |journal=Advances in Colloid and Interface Science |volume=165 |issue=1 |pages=36–46 |date=2011 |last1=Maldonado-Valderrama |first1=Julia |last2=Wilde |first2=Pete |last3=MacIerzanka |first3=Adam |last4=MacKie |first4=Alan}}]
Certain caterpillars (of the moth species [Spodoptera exigua](/source/Spodoptera_exigua), South East Asia) spit a surfactant-containing secretion at predators. This deters attacking ants, allowing the caterpillars to escape. The surfactants in the caterpillars' oral secretions reduce its surface tension. Instead of rolling off the ants' water-repellent skin like normal water, the secretion soaks the attackers. The affected ants then clean themselves, which gives the caterpillar enough time to escape.[{{Cite journal |last1=Rostás |first1=Michael |last2=Blassmann |first2=Katrin |date=22 February 2009 |title=Insects had it first: surfactants as a defence against predators |journal=Proceedings of the Royal Society B: Biological Sciences |volume=276 |issue=1657 |pages=633–638 |doi=10.1098/rspb.2008.1281 |issn=0962-8452 |pmc=2660939 |pmid=18986976}}]
== Safety and environmental risks ==
Most anionic and non-ionic surfactants are non-toxic, having [LD50](/source/LD50) comparable to [table salt](/source/NaCl). The toxicity of [quaternary ammonium compounds](/source/quaternary_ammonium_compounds), which are [antibacterial](/source/antibacterial) and [antifungal](/source/antifungal), varies. Dialkyldimethylammonium chlorides ([DDAC](/source/DDAC), [DSDMAC](/source/DSDMAC)) used as [fabric softener](/source/fabric_softener)s have high LD50 (5 g/kg) and are essentially non-toxic, while the [disinfectant](/source/disinfectant) alkylbenzyldimethylammonium chloride has an LD50 of 0.35 g/kg. Prolonged exposure to surfactants can irritate and damage the skin because surfactants disrupt the [lipid membrane](/source/lipid_membrane) that protects skin and other cells. Skin irritancy generally increases in the series non-ionic, amphoteric, anionic, cationic surfactants.[{{cite journal |last1=Metcalfe |first1=T. L. |last2=Dillon |first2=P. J. |last3=Metcalfe |first3=C. D. |title=Detecting the transport of toxic pesticides from golf courses into watersheds in the Precambrian Shield region of Ontario, Canada |journal=Environmental Toxicology and Chemistry |volume=27 |issue=4 |pages=811–8 |date=April 2008 |pmid=18333674 |doi=10.1897/07-216.1 |bibcode=2008EnvTC..27..811M |s2cid=39914076}}][{{Cite web |title=Simultaneous analysis of cationic, anionic and neutral surfactants from different matrices using LC/MS/MS {{!}} SHIMADZU (Shimadzu Corporation)|url= https://www.shimadzu.com/an/literature/lcms/apo112145.html|access-date=14 November 2021|website=www.shimadzu.com|archive-date=14 November 2021|archive-url= https://web.archive.org/web/20211114134903/https://www.shimadzu.com/an/literature/lcms/apo112145.html|url-status=live}}][{{cite journal |last1=Murphy |first1=M. G. |last2=Al-Khalidi |first2=M. |last3=Crocker |first3=J. F. |last4=Lee |first4=S. H. |last5=O'Regan |first5=P. |last6=Acott |first6=P. D. |title=Two formulations of the industrial surfactant, Toximul, differentially reduce mouse weight gain and hepatic glycogen in vivo during early development: effects of exposure to Influenza B Virus |journal=Chemosphere |volume=59 |issue=2 |pages=235–46 |date=April 2005 |pmid=15722095 |doi=10.1016/j.chemosphere.2004.11.084 |bibcode=2005Chmsp..59..235M}}]
Anionic surfactants can be found in soils as the result of [sewage sludge](/source/sewage_sludge) application, wastewater irrigation, and remediation processes. Relatively high concentrations of surfactants together with multimetals can represent an environmental risk. At low concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility.[{{cite journal |last1=Hernández-Soriano |first1=Maria del Carmen |last2=Degryse |first2=Fien |last3=Smolders |first3=Erik |title=Mechanisms of enhanced mobilisation of trace metals by anionic surfactants in soil |journal=Environmental Pollution |volume=159 |issue=3 |pages=809–16 |date=March 2011 |pmid=21163562 |doi=10.1016/j.envpol.2010.11.009 |bibcode=2011EPoll.159..809H}}][{{cite journal |last1=Hernández-Soriano |first1=Maria del Carmen |last2=Peña |first2=Aránzazu |last3=Dolores Mingorance |first3=Ma |title=Release of metals from metal-amended soil treated with a sulfosuccinamate surfactant: effects of surfactant concentration, soil/solution ratio, and pH |journal=Journal of Environmental Quality |volume=39 |issue=4 |pages=1298–305 |date=2010 |pmid=20830918 |doi=10.2134/jeq2009.0242 |bibcode=2010JEnvQ..39.1298H}}]
In the case of the [Deepwater Horizon oil spill](/source/Deepwater_Horizon_oil_spill), unprecedented amounts of [Corexit](/source/Corexit) were sprayed directly into the ocean at the leak and on the sea-water's surface. The apparent theory was that the surfactants isolate droplets of oil, making it easier for petroleum-consuming microbes to digest the oil. The active ingredient in Corexit is [dioctyl sodium sulfosuccinate](/source/dioctyl_sodium_sulfosuccinate) (DOSS), [sorbitan monooleate](/source/sorbitan_monooleate) (Span 80), and polyoxyethylenated sorbitan monooleate ([Tween-80](/source/Tween-80)).[{{cite web |url= http://emsa.europa.eu/opr-documents/opr-manual-a-guidelines/download/1166/719/23.html |title=European Maritime Safety Agency. Manual on the Applicability of Oil Dispersants; Version 2; 2009. |access-date=19 May 2017 |url-status=live |archive-url= https://web.archive.org/web/20110705151503/http://www.emsa.europa.eu/opr-documents/opr-manual-a-guidelines/download/1166/719/23.html |archive-date=5 July 2011 }}][{{cite book |url= https://www.nap.edu/read/736/chapter/1 |title=Using Oil Spill Dispersants on the Sea |author=((Committee on Effectiveness of Oil Spill Dispersants, National Research Council Marine Board)) |date=1989 |publisher=National Academies Press |doi=10.17226/736 |isbn=978-0-309-03889-8 |access-date=31 October 2015 |archive-date=3 January 2019 |archive-url= https://web.archive.org/web/20190103110128/https://www.nap.edu/read/736/chapter/1 |url-status=live}}]
===Biodegradation===
Because of the volume of surfactants released into the environment, for example laundry detergents in waters, their biodegradation is of great interest. Attracting much attention is the non-biodegradability and extreme persistence of [fluorosurfactant](/source/fluorosurfactant), e.g. [perfluorooctanoic acid](/source/perfluorooctanoic_acid) (PFOA).[USEPA: [http://www.epa.gov/opptintr/pfoa/pubs/pfoastewardship.htm "2010/15 PFOA Stewardship Program"] {{webarchive|url= https://web.archive.org/web/20081027061359/http://www.epa.gov/opptintr/pfoa/pubs/pfoastewardship.htm|date=27 October 2008}} Accessed 26 October 2008.] Strategies to enhance degradation include [ozone](/source/ozone) treatment and biodegradation.[{{cite journal |doi=10.1007/s10311-014-0466-2 |title=Surfactants: Toxicity, remediation and green surfactants |date=2014 |last1=Rebello |first1=Sharrel |last2=Asok |first2=Aju K. |last3=Mundayoor |first3=Sathish |last4=Jisha |first4=M. S. |journal=Environmental Chemistry Letters |volume=12 |issue=2 |pages=275–287 |bibcode=2014EnvCL..12..275R |s2cid=96787489}}][{{cite journal |doi=10.1016/j.envint.2005.07.004 |title=Fate, behavior and effects of surfactants and their degradation products in the environment |date=2006 |last1=Ying |first1=Guang-Guo |journal=Environment International |volume=32 |issue=3 |pages=417–431 |pmid=16125241 |bibcode=2006EnInt..32..417Y}}] Two major surfactants, [linear alkylbenzene sulfonate](/source/linear_alkylbenzene_sulfonate)s (LAS) and the alkyl phenol [ethoxylate](/source/ethoxylate)s (APE) break down under aerobic conditions found in [sewage treatment](/source/sewage_treatment) plants and in soil to [nonylphenol](/source/nonylphenol), which is thought to be an [endocrine disruptor](/source/endocrine_disruptor).[Mergel, Maria. "Nonylphenol and Nonylphenol Ethoxylates." Toxipedia.org. N.p., 1 November 2011. Web. 27 April 2014.][{{cite journal |last1=Scott |first1=M. J. |last2=Jones |first2=M. N. |title=The biodegradation of surfactants in the environment |journal=Biochimica et Biophysica Acta (BBA) - Biomembranes |volume=1508 |issue=1–2 |pages=235–51 |date=November 2000 |pmid=11090828 |doi=10.1016/S0304-4157(00)00013-7 |doi-access=free}}] Interest in biodegradable surfactants has led to much interest in "biosurfactants" such as those derived from amino acids.[{{cite journal |last1=Reznik |first1=G. O. |last2=Vishwanath |first2=P. |last3=Pynn |first3=M. A. |last4=Sitnik |first4=J. M. |last5=Todd |first5=J. J. |last6=Wu |first6=J. |last7=Jiang |first7=Y. |last8=Keenan |first8=B. G. |last9=Castle |first9=A. B. |last10=Haskell |first10=R. F. |last11=Smith |first11=T. F. |last12=Somasundaran |first12=P. |last13=Jarrell |first13=K. A. |title=Use of sustainable chemistry to produce an acyl amino acid surfactant |journal=Applied Microbiology and Biotechnology |volume=86 |issue=5 |pages=1387–97 |date=May 2010 |pmid=20094712 |doi=10.1007/s00253-009-2431-8 |s2cid=3017826}}] Biobased surfactants can offer improved biodegradation. However, whether surfactants damage the cells of fish or cause foam mountains on bodies of water depends primarily on their chemical structure and not on whether the carbon originally used came from fossil sources, carbon dioxide or biomass.