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| [[File:Dispersant Mechanism.jpg|thumb|Oil dispersant mechanism of action|alt=Color illustration of how oil dispersants work]]
| | This is a preview for the new '''MathML rendering mode''' (with SVG fallback), which is availble in production for registered users. |
| '''Oil dispersants''' are a mixture of [[surfactants]] and solvents that break up an [[oil spill]] into droplets. By breaking it up, microbes and the environment can more easily [[biodegrade]] the oil. A mixture of oil and water is normally unstable, but can be stabilized with the addition of surfactants. Surfactants improve interaction at the oil-water junction, decreasing surface energy. Dispersants have had negative environmental effects due to their toxicity; however, reformulated dispersants have been accepted by the [[United States Environmental Protection Agency]] (EPA).<ref>{{cite web|title=Dispersants|url=http://www.epa.gov/bpspill/dispersants.html}}</ref> | |
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| ==History==
| | If you would like use the '''MathML''' rendering mode, you need a wikipedia user account that can be registered here [[https://en.wikipedia.org/wiki/Special:UserLogin/signup]] |
| In 1967, the ''Torrey Canyon'' leaked oil onto the [[Torrey Canyon oil spill|English coastline]].<ref name=Clayton /> [[Alkylphenol]] surfactants were primarily used to break up the oil, but proved very toxic in the marine environment; all types of marine life were killed. This led to a reformulation of dispersants to be more environmentally sensitive. After the Torrey Canyon spill, new boat-spraying systems were developed.<ref name=Clayton /> Later reformulations allowed more dispersant to be contained (at a higher concentration) to be aerosolized.
| | * Only registered users will be able to execute this rendering mode. |
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| ==Theory==
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| ===Requirements===
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| There are five requirements for surfactants to successfully disperse oil:<ref name=Clayton/>
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| *Dispersant must be on the oil's surface in the proper concentration
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| *Dispersant must penetrate (mix with) the oil
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| * Surfactant molecules must orient at the oil-water interface (hydrophobic in oil and [[Hydrophile|hydrophilic]] in water)
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| * Oil-water interfacial surface tension must be lowered (so the oil can be broken up).
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| * Energy must be applied to the mix (for example, by waves)
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| The [[hydrophilic-lipophilic balance]] (HLB) is a coding scale from 0 to 20 for non-[[ion]]ic surfactants, and takes into account the chemical structure of the surfactant molecule. A zero value corresponds to the most [[Lipophilicity|lipophilic]] and a value of 20 is the most hydrophilic for a non-ionic surfactant.<ref name=Clayton>{{cite book|last=Clayton|first=John R.|title=Oil Spill Dispersants: Mechanisms of Action and Laboratory Tests|year=1992|publisher= C K Smoley & Sons|isbn=0-87371-946-8|pages=9-23}}</ref>[[File:Oil with Surfactant.jpg|thumb|left|Oil reacting with surfactant in water|alt=Illustration of oil reacting with surfactant in water]]
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| | :<math forcemathmode="mathml">E=mc^2</math> |
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| ==={{anchor|Dispersion Models}}Dispersion models===
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| Developing well-constructed models (accounting for variables such as oil type, salinity and surfactant) are necessary to select the appropriate dispersant in a given situation. Two models exist which integrate the use of dispersants: Mackay's model and Johansen's model.<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill Dispersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref> There are several parameters which must be considered when creating a dispersion model, including oil-slick thickness, [[advection]], resurfacing and wave action.<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill Dispersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref> A general problem in modeling dispersants is that they change several of these parameters; surfactants lower the thickness of the film, increase the amount of diffusion into the water column and increase the amount of breakup caused by wave action. This causes the oil slick's behavior to be more dominated by vertical diffusion than horizontal advection.<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill Dispersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref>
| | :<math forcemathmode="png">E=mc^2</math> |
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| One equation for the modeling of oil spills is:<ref name= "Tkalich"> Tkalich,P Xiaobo,C Accurate Simulation of Oil Slicks, Tropical marine science institute, Presented 2001 International Oil Spill Conference pp 1133-1135 http://www.iosc.org/papers_posters/00015.pdf</ref>
| | '''source''' |
| | :<math forcemathmode="source">E=mc^2</math> --> |
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| <math>(\frac {\partial h}{\partial t})\bigtriangledown (h(\vec {U} + (\frac {\vec {t}}{f}) - \bigtriangledown(E\bigtriangledown h) = R </math> | | <span style="color: red">Follow this [https://en.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering link] to change your Math rendering settings.</span> You can also add a [https://en.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering-skin Custom CSS] to force the MathML/SVG rendering or select different font families. See [https://www.mediawiki.org/wiki/Extension:Math#CSS_for_the_MathML_with_SVG_fallback_mode these examples]. |
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| | ==Demos== |
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| * ''h'' is the oil-slick thickness
| | Here are some [https://commons.wikimedia.org/w/index.php?title=Special:ListFiles/Frederic.wang demos]: |
| * <math>\vec {U}</math> is the velocity of ocean currents in the mixing layer of the water column (where oil and water mix together)
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| * <math>\vec {t}</math> is the wind-driven shear stress
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| * ''f'' is the oil-water friction coefficient
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| * ''E'' is the relative difference in densities between the oil and water
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| * ''R'' is the rate of spill propagation
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| Mackay's model predicts an increasing dispersion rate, as the slick becomes thinner in one dimension. The model predicts that thin slicks will disperse faster than thick slicks for several reasons. Thin slicks are less effective at dampening waves and other sources of turbidity. Additionally, droplets formed upon dispersion are expected to be smaller in a thin slick and thus easier to disperse in water.
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| The model also includes:<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill Dispersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref>
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| * An expression for the diameter of the oil drop | | * accessibility: |
| * Temperature dependence of oil movement | | ** Safari + VoiceOver: [https://commons.wikimedia.org/wiki/File:VoiceOver-Mac-Safari.ogv video only], [[File:Voiceover-mathml-example-1.wav|thumb|Voiceover-mathml-example-1]], [[File:Voiceover-mathml-example-2.wav|thumb|Voiceover-mathml-example-2]], [[File:Voiceover-mathml-example-3.wav|thumb|Voiceover-mathml-example-3]], [[File:Voiceover-mathml-example-4.wav|thumb|Voiceover-mathml-example-4]], [[File:Voiceover-mathml-example-5.wav|thumb|Voiceover-mathml-example-5]], [[File:Voiceover-mathml-example-6.wav|thumb|Voiceover-mathml-example-6]], [[File:Voiceover-mathml-example-7.wav|thumb|Voiceover-mathml-example-7]] |
| * An expression for the resurfacing of oil | | ** [https://commons.wikimedia.org/wiki/File:MathPlayer-Audio-Windows7-InternetExplorer.ogg Internet Explorer + MathPlayer (audio)] |
| * Calibrations based on data from experimental spills | | ** [https://commons.wikimedia.org/wiki/File:MathPlayer-SynchronizedHighlighting-WIndows7-InternetExplorer.png Internet Explorer + MathPlayer (synchronized highlighting)] |
| | ** [https://commons.wikimedia.org/wiki/File:MathPlayer-Braille-Windows7-InternetExplorer.png Internet Explorer + MathPlayer (braille)] |
| | ** NVDA+MathPlayer: [[File:Nvda-mathml-example-1.wav|thumb|Nvda-mathml-example-1]], [[File:Nvda-mathml-example-2.wav|thumb|Nvda-mathml-example-2]], [[File:Nvda-mathml-example-3.wav|thumb|Nvda-mathml-example-3]], [[File:Nvda-mathml-example-4.wav|thumb|Nvda-mathml-example-4]], [[File:Nvda-mathml-example-5.wav|thumb|Nvda-mathml-example-5]], [[File:Nvda-mathml-example-6.wav|thumb|Nvda-mathml-example-6]], [[File:Nvda-mathml-example-7.wav|thumb|Nvda-mathml-example-7]]. |
| | ** Orca: There is ongoing work, but no support at all at the moment [[File:Orca-mathml-example-1.wav|thumb|Orca-mathml-example-1]], [[File:Orca-mathml-example-2.wav|thumb|Orca-mathml-example-2]], [[File:Orca-mathml-example-3.wav|thumb|Orca-mathml-example-3]], [[File:Orca-mathml-example-4.wav|thumb|Orca-mathml-example-4]], [[File:Orca-mathml-example-5.wav|thumb|Orca-mathml-example-5]], [[File:Orca-mathml-example-6.wav|thumb|Orca-mathml-example-6]], [[File:Orca-mathml-example-7.wav|thumb|Orca-mathml-example-7]]. |
| | ** From our testing, ChromeVox and JAWS are not able to read the formulas generated by the MathML mode. |
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| The model is lacking in several areas: it does not account for evaporation, the topography of the ocean floor or the geography of the spill zone.<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill DIspersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref>
| | ==Test pages == |
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| Johansen's model is more complex than Mackay's model. It considers particles to be in one of three states: at the surface, [[entrainment|entrained]] in the water column or evaporated. The empirically based model uses probabilistic variables to determine where the dispersant will move and where it will go after it breaks up oil slicks. The drift of each particle is determined by the state of that particle; this means that a particle in the vapor state will travel much further than a particle on the surface (or under the surface) of the ocean.<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill DIspersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref> This model improves on Mackay's model in several key areas, including terms for:<ref name="Using Oil Dispersants">National Research Council Committee on Effectiveness of Oil Spill DIspersants: Using Oil Dispersants on the Sea, National Academy Press, 1989 pp 63-75</ref>
| | To test the '''MathML''', '''PNG''', and '''source''' rendering modes, please go to one of the following test pages: |
| | *[[Displaystyle]] |
| | *[[MathAxisAlignment]] |
| | *[[Styling]] |
| | *[[Linebreaking]] |
| | *[[Unique Ids]] |
| | *[[Help:Formula]] |
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| * Probability of [[entrainment]] – depends on wind | | *[[Inputtypes|Inputtypes (private Wikis only)]] |
| * Probability of resurfacing – depends on density, droplet size, time submerged and wind
| | *[[Url2Image|Url2Image (private Wikis only)]] |
| * Probability of evaporation – matched with empirical data
| | ==Bug reporting== |
| | | If you find any bugs, please report them at [https://bugzilla.wikimedia.org/enter_bug.cgi?product=MediaWiki%20extensions&component=Math&version=master&short_desc=Math-preview%20rendering%20problem Bugzilla], or write an email to math_bugs (at) ckurs (dot) de . |
| Oil dispersants are modeled by Johansen using a different set of entrainment and resurfacing parameters for treated versus untreated oil. This allows areas of the oil slick to be modeled differently, to better understand how oil spreads along the water's surface.
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| == Thermodynamics ==
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| === {{anchor|Non-Ionic Surfactants}}Non-ionic surfactants ===
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| To determine the [[Gibbs free energy]] of [[Micelle|micellization]], the change in chemical potential for the surfactant going from a single [[Solvation|solvated]] [[molecule]] to a micelle is measured. There are many approaches to this, one of which is the ''phase-separation model''. This model takes advantage of the fact that micellization resembles two phases separated by a [[monolayer]]. However, the model does not take into account changes in energy associated with the interactions of charges and is suitable only for describing non-ionic surfactants.<ref name="Butt"> Butt, Hans-Jürgen. Graf, Karlheinz. Kappl, Michael. "Physics and Chemistry of Interfaces". 2nd Edition. WILEY-VCH. pp 265-299. 2006.</ref> In the phase-separation model, there are two distinct phases: alpha(α) and beta(β). The [[surface tension]] between the two phases is described by the [[Laplace Equation]], which relates the change in pressure across two phases to the curvature and surface tension.
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| <math> \Delta P= \gamma (C_1 +C_2)</math>
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| where:
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| <math> \Delta P</math> is the change in pressure across the interface
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| <math>\gamma</math> is the surface tension
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| <math>C_1 </math>and <math>C_2</math> are the curvatures of the selected interface
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| The chemical potential, μ, at low concentrations can be described by the equation:<ref name=Butt />
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| <math>\mu _{sur} (micelle) = \mu ^0 _{sur} + RTln[S]</math>
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| When ''[S]'' (the concentration of surfactant) reaches the [[critical micelle concentration]], the chemical potential of the surfactant in the micelle is equal to the chemical potential of the surfactant when it is solvated.<ref name=Butt />
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| Thus, the Gibbs free energy of micelle formation is described by the equation:
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| <math>\Delta G^{mic} _m = \mu_{micelle} - \mu^{0} _{sur} = RTlnCMC</math>
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| The main factor driving the formation of micelles, the movement of [[aliphatic compound]]s out of water and into an environment where they can interact with other non-polar groups, is driven by [[Introduction to entropy|entropy]]. Although there is [[Order and disorder (physics)|ordering]] occurring by means of a phase separation, the entropy gained by the water molecules interacting with other water molecules is far greater in magnitude.<ref name=Butt />
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| === {{anchor|Ionic Surfactants}}Ionic surfactants === | |
| [[File:C-130_support_oil_spill_cleanup.jpg|thumb|U.S. Air Force C-130 plane releases dispersants over the [[''Deepwater Horizon'' oil spill]].|alt=Plane spraying dispersants over an oil spill]]
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| Describing the formation of micelles mathematically for ionic surfactants is far more difficult because of the repulsion that occurs between the head groups as the micelle is formed.<ref name=Butt /> The surfactant molecules must also be dehydrated prior to micelle formation (which decreases the shielding of each head group, thus increasing the repulsion between two molecules). For this reason, the [[critical micelle concentration]] (CMC) of ionic surfactants tends to be higher than that of their non-ionic counterparts.<ref name=Butt /> . When addressing ionic surfactants, one must consider the [[electric double layer]] that forms at the surface of the micelle.
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| <ref name="Rusanov"> Rusanov, A I. Thermodynamics of Ionic Micelles. Russian Chemical Reviews Vol 58(2) pp101-113 (1989)</ref> This double layer has the effect of stabilizing the micelle by shielding the like charges from each head group. Adding salt to ionic surfactants has the effect of drastically reducing the CMC. The salt increases the concentration of ions available to screen the charge of the ionic head groups, and will thus make it easier for [[particle aggregation]] to occur. Another method to reduce the CMC of an ionic micelle is to increase the length of the [[Alkane|alkyl]] chain, increasing the amount of [[Dispersion (chemistry)|dispersion interactions]] and thus making micelle formation more energetically favorable. <ref name=Butt />
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| Ionic micelles are very difficult to describe mathematically due to the repulsion occurring between all head groups, the number of variables and the fact that the electric potential felt by each head group is dependent on the other groups.
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| =={{anchor|Types of Surfactants}}Surfactant types==
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| There are four main types of surfactants, each with different properties and applications: [[anion]]ic, cationic, nonionic and [[zwitterion]]ic (or amphoteric). Anionic surfactants are compounds that contain an anionic polar group. Examples of anionic surfactants include [[sodium dodecyl sulfate]] and [[dioctyl sodium sulfosuccinate]].<ref name="Butler et. al." /> Included in this class of surfactants are sodium alkylcarboxylates (soaps).<ref name=Butt /> Cationic surfactats are similar in nature to anionic surfactants, except the surfactant molecules carry a positive charge at the hydrophilic portion. Many of these compounds are [[Quaternary ammonium cation|quaternary ammonium salts]], as well as [[cetrimonium bromide]] (CTAB). <ref name=Butt /> Non-ionic surfactants are non-charged and together with anionic surfactants make up the majority of oil-dispersant formulations.<ref name="Butler et. al." /> The hydrophilic portion of the surfactant contains polar [[functional groups]], such as -OH or -NH.<ref name=Butt /> Zwitterionic surfactants are the most expensive, and are used for specific applications.<ref name=Butt /> These compounds have both positively and negatively charged components. An example of a zwitterionic compound is [[phosphatidylcholine]], which as a lipid is largely insoluble in water.<ref name=Butt />
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| =={{anchor|HLB Values}}HLB values==
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| Surfactant behavior is highly dependent on the [[hydrophilic-lipophilic balance]] (HLB) value. In general, compounds with an HLB between one and four will not mix with water. Compounds with an HLB value above 13 will form a clear solution in water.<ref name="Butler et. al."> Using Oil Spill Dispersants. National Academy Press. pp 29-32 1989</ref> Oil dispersants usually have HLB values from 8–18.<ref name="Butler et. al." />
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| {{anchor|Table of HLB Values for Various Surfactants}}
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| {| class="wikitable" style="text-align: center"
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| |+ HLB values for various surfactants
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| ! Surfactant !! Structure !! Avg mol wt !! HLB
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| | Arkopal N-300 || C<sub>9</sub>H<sub>19</sub>C<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>30</sub>H || 1,550 || 17.0<ref name=Tiehm />
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| | Brij 30 || polyoxyethylenated straight chain alcohol || 362 || 9.7<ref name=Grimberg>{{cite journal|last=Grimberg|first=S.J.|coauthors=Nagel, J; Aitken, M.D.|title=Kinetics of phenanthrene dissolution into water in the presence of nonionic surfactants.|journal=Environ. Sci. Technol.|year=1995|month=June|volume=29|issue=6|pages=1480-1487|doi=10.1021/es00006a008}}</ref>
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| | Brij 35 || C<sub>12</sub>H<sub>25</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>23</sub>H || 1,200 || 17.0<ref name=Tiehm />
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| | Brij 56 || C<sub>16</sub>H<sub>33</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>10</sub>H || 682 || 12.9<ref name=Egan>{{cite journal|last=Egan|first=Robert|coauthors=Lehninger, A., Jones, M.A.|title=Hydrophile-Lipophile Balance and Critical Micelle Concentration as Key Factors Influencing Surfactant Disruption of Mitochondrial Membranes|journal=Journal of Biological Chemistry|date=January 26, 1976|year=1976|month=January|volume=251|series=14|pages=4442-4447}}</ref>
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| | Brij 58 || C<sub>16</sub>H<sub>33</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>20</sub>H || 1122 || 15.7<ref name=Egan />
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| | EGE Coco || ethyl glucoside || 415 || 10.6<ref name=Grimberg />
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| | EGE no. 10 || ethyl glucoside || 362 || 12.5<ref name=Grimberg />
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| | Genapol X-150 || C<sub>13</sub>H<sub>27</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>15</sub>H || 860 || 15.0<ref name=Tiehm />
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| | Tergitol NP-10 || nonylphenolethoxylate || 682 || 13.6<ref name=Grimberg />
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| | Marlipal 013/90 || C<sub>13</sub>H<sub>27</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>9</sub>H || 596 || 13.3<ref name=Tiehm>{{cite journal|last=Tiehm|first=Andreas|title=Degradation of polycyclic aromatic hydrocarbons in the presence of synthetic surfactants.|journal=Appl. Environ. Microbiol.|year=1994|month=January|volume=60|issue=1|pages=258-263|url=http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=8117081&retmode=ref&cmd=prlinks}}</ref>
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| | Pluronic PE6400 || HO(CH<sub>2</sub>CH<sub>2</sub>O)<sub>x</sub>(C<sub>2</sub>H<sub>4</sub>CH<sub>2</sub>O)<sub>30</sub>(CH<sub>2</sub>CH<sub>2</sub>O)<sub>28-x</sub>H || 3000 || N.A.<ref name=Tiehm />
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| | Sapogenat T-300 || (C<sub>4</sub>H<sub>9</sub>)<sub>3</sub>C<sub>6</sub>H<sub>2</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>30</sub>H || 1600 || 17.0<ref name=Tiehm />
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| | T-Maz 60K || ethoxylated sorbitan monostearate || 1310 || 14.9<ref name=Grimberg />
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| | T-Maz 20 || ethoxylated sorbitan monolaurate || 1226 || 16.7<ref name=Grimberg />
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| | Triton X-45 || C<sub>8</sub>H<sub>17</sub>C<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>5</sub>H || 427 || 10.4<ref name=Egan />
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| | Triton X-100 || C<sub>8</sub>H<sub>17</sub>C<sub>6</sub>H<sub>4</sub>(OC<sub>2</sub>H<sub>4</sub>)<sub>10</sub>OH || 625 || 13.6<ref name=Kim>{{cite journal|last=Kim|first=I.S.|coauthors=Park, J.S.; Kim, K.W.|title=Enhanced biodegradation of polycyclic aromatic hydrocarbons using nonionic surfactants in soil slurry|journal=Applied Geochemistry|year=2001|volume=16|issue=11-12|pages=1419-1428|url=http://www.sciencedirect.com/science/article/pii/S0883292701000439}}</ref>
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| | Triton X-102 || C<sub>8</sub>H<sub>17</sub>C<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>12</sub>H || 756 || 14.6<ref name=Tiehm />
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| | Triton X-114 || C<sub>8</sub>H<sub>17</sub>C<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>7.5</sub>H || 537 || 12.4<ref name=Egan />
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| | Triton X-165 || C<sub>8</sub>H<sub>17</sub>C<sub>6</sub>H<sub>4</sub>O(CH<sub>2</sub>CH<sub>2</sub>O)<sub>16</sub>H || 911 || 15.8<ref name=Egan />
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| | Tween 80 || C<sub>18</sub>H<sub>37</sub>-C<sub>6</sub>H<sub>9</sub>O<sub>5</sub>-(OC<sub>2</sub>H<sub>4</sub>)<sub>20</sub>OH || 1309 || 13.4<ref name=Kim />
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| |}
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| == {{anchor|Comparative Industrial Formulations}}Comparative industrial formulations ==
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| Two formulations of different dispersing agents for oil spills, DISPERSIT and Omni-Clean, are shown below. A key difference between the two is that Omni-Clean uses ionic surfactants and DISPERSIT uses entirely non-ionic surfactants. Omni-Clean was formulated for little or no toxicity toward the environment. DISPERSIT, however, was designed as a competitor with COREXIT. DISPERSIT contains non-ionic surfactants, which permit both primarily oil-soluble and primarily water-soluble surfactants. The partitioning of surfactants between the phases allows for effective dispersion.
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| {| class="wikitable" border="1"
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| ! colspan="4" style="background: #efefef;" | Omni-Clean OSD <ref>{{ cite patent
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| | country = US
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| | number = 4992213
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| | status = patent
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| | title = Cleaning composition, oil dispersant and use thereof
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| | pubdate = 1991-02-12
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| | fdate = 1989-06-23
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| | inventor = G. Troy Mallett, Edward E. Friloux, David I. Foster
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| }}</ref>
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| ! colspan="4" style="background: #efefef;" | DISPERSIT <ref>{{ cite patent
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| | country = US
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| | number = 6261463
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| | status = patent
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| | title = Water based oil dispersant
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| | pubdate = 2001-07-17
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| | fdate = 1999-03-4
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| | inventor = Savarimuthu M. Jacob, Robert E. Bergman, Jr.
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| | assign1 = U.S. Polychemical Marine Corp.
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| }}</ref>
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| ! Category !! colspan="2" |Ingredient !! Function !! Category !! colspan="2" |Ingredient !! Function
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| | Surfactant || [[File:Sodium_laurylsulfonate_V.1.svg|199x65px]] || Sodium lauryl sulfate || Charged ionic surfactant and thickener || Emulsifying agent || [[File:Oleic Acid Sorbitan Monoester.png|Oleic Acid Sorbitan Monoester|199x65px]] || Oleic acid sorbitan monoester || Emulsifying agent
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| | Surfactant || [[File:Cocamidopropyl betaine2.png|199x65px]] || Cocamidopropyl betaine || Emulsifying agent || Surfactant || [[File:Coconut oil monoethanolamide.png|199x65px]] || Coconut oil monoethanolamide || Dissolves oil and water into each other
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| | Surfactant || [[File:Nonoxynol-9.png|199x65px]] || Ethoxylated nonylphenol || Petroleum emulsifier & wetting agent|| Surfactant || [[File:Poly(ethylene glycol) monooleate.png|199x65px]] || Poly(ethylene glycol) monooleate || Oil-soluble surfactant
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| | Dispersant || [[File:Cocamide_DEA.png|199x65px]] || Lauric acid diethanolamide || Non-ionic viscosity booster & emulsifier || Surfactant || [[File:Polyethoxylated_tallow_amine.svg|199x65px]] || Polyethoxylated tallow amine || Oil-soluble surfactant
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| | Detergent || [[File:Diethanolamine.png|199x65px]] || Diethanolamine || Water-soluble detergent for cutting oil || Surfactant || [[File:Polyethoxylated linear secondary alcohol.png|199x65px]] || Polyethoxylated linear secondary alcohol || Oil-soluble surfactant
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| | Emulsifier || [[File:Propylene_glycol_chemical_structure.png|199x65px]] || Propylene glycol || Solvent for oils, wetting agent, emulsifier || Solvent || [[File:Dipropylene glycol methyl ether.png|199x65px]] || Dipropylene glycol methyl ether || Enhances solubility of surfactants in water and oil.
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| | Solvent || H<sub>2</sub>O || Water || Reduces viscosity || Solvent || H<sub>2</sub>O || Water || Reduces viscosity
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| |}
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| =={{anchor|Degradation and Toxicity}}Degradation and toxicity==
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| Both the degradation and the toxicity of dispersants depend on the chemicals chosen within the formulation. Compounds which interact too harshly with oil dispersants should be tested to ensure that they meet three criteria:<ref name=Mulkins>{{cite journal|last=Mulkins-Phillips|first=G. J.|coauthors=Stewart, J.E.|title=Effect of Four Dispersants on Biodegradation and Growth of Bacteria on Crude Oil|journal=Applied Microbiology|date=October|year=1974|volume=28|pages=547-552}}</ref>
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| * They should be biodegradable.
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| * In the presence of oil, they must not be preferentially utilized as a carbon source.
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| * They must be nontoxic to indigenous bacteria.
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| ==Applications==
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| ==={{anchor|Oil Treatment}}Oil treatment===
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| The effectiveness of the dispersant depends on the weathering of the oil, sea energy (waves), salinity of the water, temperature and the type of oil.<ref name=Fingas>{{cite book|last=Fingas|first=Merv|title=The Basics of Oil Spill Cleanup|year=2001|publisher=Lewis Publishers|isbn=1-56670-537-1|pages=120-125}}</ref> Dispersion is unlikely to occur if the oil spreads into a thin layer, because the dispersant requires a particular thickness to work; otherwise, the dispersant will interact with both the water and the oil. More dispersant may be required if the sea energy is low. The salinity of the water is more important for ionic-surfactant dispersants, since they will preferentially interact with the water more than the oil.
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| The [[viscosity]] of the oil is another important factor; viscosity can retard dispersant migration to the oil-water interface and also increase the energy required to shear a drop from the slick. Viscosities below 2,000 centi[[poise]] are optimal for dispersants. If the viscosity is above 10,000 centipoise, no dispersion is possible.<ref name=NRC>{{cite book|last=National Research Council (U.S.)|title=Using Oil Spill Dispersants on the Sea|year=1989|publisher=National Academy Press|location=Washington, D.C.|pages=54}}</ref>
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| =={{anchor|Methods of Use}}Methods of use==
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| Dispersants are delivered in concentrated, dilute solutions and are aerosolized by aerial spraying (typically by an aircraft or boat). Sufficient dispersant with droplets in the proper size are necessary; this can be achieved with an appropriate pumping rate. Droplets larger than 1,000 µm are preferred, to ensure they are not blown away by the wind. The ratio of dispersant to oil is typically 1:20.<ref name=Fingas />
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| == {{anchor|Oil Spills and Dispersants Used}}Oil spills and dispersants used ==
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| === {{anchor|Deep Water Horizion}}''Deepwater Horizon'' ===
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| During the Deepwater Horizon oil spill, an estimated 1.84 million gallons of oil dispersants were used in an attempt to reduce the amount of surface oil and mitigate the damage to wildlife. Nearly half (771,000 gallons) of the dispersants were applied directly at the wellhead.<ref name="Gov't Commission">National Commission on the BP Deepwater Horizon Oil Spill and Offshore DrillingTHE USE OF SURFACE AND SUBSEA DISPERSANTS DURING THE BP DEEPWATER HORIZON OIL SPILL http://www.oilspillcommission.gov/sites/default/files/documents/Updated%20Dispersants%20Working%20Paper.pdf accessed 5/23/2012</ref> The primary dispersant used was [[Corexit]], which was controversial due to its toxicity relative to other dispersants.
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| ==={{anchor|Exxon Valdez}}''Exxon Valdez''===
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| {{Main|Exxon Valdez oil spill}}
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| Dispersants were also used during the Exxon Valdez oil spill, although their use was far less effective. Alaska had fewer than 4,000 gallons of dispersants available at the time of the incident, and no aircraft with which to dispense them. The dispersants introduced were relatively ineffective (due to insufficient wave action to mix the oil and water), and their use was shortly abandoned. <ref name="epa">EPA: Learning Center: Exxon Valdez. http://www.epa.gov/oem/content/learning/exxon.htm accessed 5/23/2012</ref>
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| ==References==
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| {{Reflist}}
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| [[Category:Oil spills]]
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| [[Category:Environmental issues]]
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| [[Category:Environmental chemistry]]
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