Dispersant

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A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their settling or clumping. [1]

Contents

Dispersants are widely used to stabilize various industrial and artisanal products, such as paints, ferrofluids, and salad dressings. The plasticizers or superplasticizers, used to improve the workability of pastes like concrete and clay, are typically dispersants. The concept also largely overlaps with that of detergent, used to bring oily contamination into water suspension, and of emulsifier, used to create homogeneous mixtures of immiscible liquids like water and oil. Natural suspensions like milk and latex contain substances that act as dispersants.

Applications

Automotive

Automotive engine oils contain both detergents and dispersants. Metallic-based detergents prevent the accumulation of varnish like deposits on the cylinder walls. They also neutralize acids. Dispersants maintain contaminants in suspension.

Dispersants added to gasoline prevent the buildup of gummy residues.

Bio-dispersing

Dispersants are used to prevent formation of biofouling or biofilms in industrial processes. It is also possible to disperse bacterial slime and increase the efficiency of biocides.

Concrete and stucco

Dispersants are used as plasticizers or superplasticizers in concrete formulations to lower the use of water while retaining the needed slump (flow) property. A lower water content makes the concrete stronger and more impervious to water penetration. [2]

Similarly, dispersants are used as plasticizers in the gypsum slurry during wallboard manufacture, to reduce the amount of water used. The lower water usage allows lower energy use to dry the wallboard. [3]

Detergents

Dispersing is the principal goal in the use of detergents, which the liquid bath is water (detergents also are used as emulsifiers in some applications). Laundry detergents encase dirt and grime in miscelles, which naturally disperse.

Oil drilling

Dispersants in oil drilling aid in breaking up solids or liquids as fine particles or droplets into another medium. This term is often applied incorrectly to clay deflocculants. Clay dispersants prevent formation of "fish-eye" globules. For dispersing (emulsification) of oil into water (or water into oils), surfactants selected on the basis of hydrophilic-lipophilic balance (HLB) number can be used. For foam drilling fluids, synthetic detergents and soaps are used, along with polymers, to disperse foam bubbles into the air or gas.

Oil spill

Dispersants can be used to dissipate oil slicks. [4] They may rapidly disperse large amounts of certain oil types from the sea surface by transferring it into the water column. They will cause the oil slick to break up and form water-soluble micelles that are rapidly diluted. Then effectively spread throughout a larger volume of water than the surface from where the oil was dispersed. They can also delay the formation of persistent oil-in-water emulsions. However, laboratory experiments showed that dispersants increased toxic hydrocarbon levels in fish by a factor of up to 100 and may kill fish eggs. [5]

Dispersant Corexit 9527 was for example used to disperse an oil slick in the Gulf of Mexico in 1979 (Ixtoc) [6] over one thousand square miles of sea. The same dispersant was also used in an attempt to clean up the Exxon Valdez oil spill [4] in 1989, though its use was discontinued as there was not enough wave action to mix the dispersant with the oil in the water. During the Deepwater Horizon oil spill in 2010, unprecedented amounts of the dispersants Corexit 9500 and 9527 were used (approximately 7 million liters). [7]

Process industry

In the process industry dispersing agents are added to process liquids to prevent unwanted deposits by keeping them finely dispersed. They function in both aqueous and nonaqueous media.

Surface coating

In order to provide optimal performance, pigment particles must act independently of each other in the coating film and thus must remain well dispersed throughout manufacture, storage, application, and film formation. Unfortunately, colloidal dispersions such as the pigment dispersions in liquid coatings are inherently unstable, and they must be stabilized against the flocculation that might occur.

See also

Related Research Articles

An emulsion is a mixture of two or more liquids that are normally immiscible owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid is dispersed in the other. Examples of emulsions include vinaigrettes, homogenized milk, liquid biomolecular condensates, and some cutting fluids for metal working.

<span class="mw-page-title-main">Surfactant</span> Substance that lowers the surface tension between a liquid and another material

Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word "surfactant" is a blend of surface-active agent, coined c. 1950. As they consist of a water-repellent and a water-attracting part, they enable water and oil to mix; they can form foam and facilitate the detachment of dirt.

<span class="mw-page-title-main">Oil spill</span> Release of petroleum into the environment

An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into the ocean or coastal waters, but spills may also occur on land. Oil spills may be due to releases of crude oil from tankers, offshore platforms, drilling rigs and wells, as well as spills of refined petroleum products and their by-products, heavier fuels used by large ships such as bunker fuel, or the spill of any oily refuse or waste oil.

In polymer chemistry, emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomers, and surfactants. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer are emulsified in a continuous phase of water. Water-soluble polymers, such as certain polyvinyl alcohols or hydroxyethyl celluloses, can also be used to act as emulsifiers/stabilizers. The name "emulsion polymerization" is a misnomer that arises from a historical misconception. Rather than occurring in emulsion droplets, polymerization takes place in the latex/colloid particles that form spontaneously in the first few minutes of the process. These latex particles are typically 100 nm in size, and are made of many individual polymer chains. The particles are prevented from coagulating with each other because each particle is surrounded by the surfactant ('soap'); the charge on the surfactant repels other particles electrostatically. When water-soluble polymers are used as stabilizers instead of soap, the repulsion between particles arises because these water-soluble polymers form a 'hairy layer' around a particle that repels other particles, because pushing particles together would involve compressing these chains.

<span class="mw-page-title-main">Plasticizer</span> Substance added to a material to make it softer and more flexible

A plasticizer is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture.

<span class="mw-page-title-main">Ixtoc I oil spill</span> Oil spill disaster in the Gulf of Mexico

Ixtoc 1 was an exploratory oil well being drilled by the semi-submersible drilling rig Sedco 135 in the Bay of Campeche of the Gulf of Mexico, about 100 km (62 mi) northwest of Ciudad del Carmen, Campeche in waters 50 m (164 ft) deep. On 3 June 1979, the well suffered a blowout resulting in the largest oil spill in history at its time. To-date, it remains the second largest oil spill in history after the Deepwater Horizon oil spill.

<span class="mw-page-title-main">2-Butoxyethanol</span> Chemical compound

2-Butoxyethanol is an organic compound with the chemical formula BuOC2H4OH. This colorless liquid has a sweet, ether-like odor, as it derives from the family of glycol ethers, and is a butyl ether of ethylene glycol. As a relatively nonvolatile, inexpensive solvent, it is used in many domestic and industrial products because of its properties as a surfactant. It is a known respiratory irritant and can be acutely toxic, but animal studies did not find it to be mutagenic, and no studies suggest it is a human carcinogen. A study of 13 classroom air contaminants conducted in Portugal reported a statistically significant association with increased rates of nasal obstruction and a positive association below the level of statistical significance with a higher risk of obese asthma and increased body mass index.

Superplasticizers (SPs), also known as high range water reducers, are additives used for making high-strength concrete or to place self-compacting concrete. Plasticizers are chemical compounds enabling the production of concrete with approximately 15% less water content. Superplasticizers allow reduction in water content by 30% or more. These additives are employed at the level of a few weight percent. Plasticizers and superplasticizers also retard the setting and hardening of concrete.

<span class="mw-page-title-main">Defoamer</span> Chemical additive that reduces and hinders the formation of foam in liquids

A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed.

<i>Deepwater Horizon</i> oil spill Oil spill in the Gulf of Mexico

The Deepwater Horizon oil spill was an environmental disaster which began on 20 April 2010, off the coast of the United States in the Gulf of Mexico on the BP-operated Macondo Prospect, considered the largest marine oil spill in the history of the petroleum industry and estimated to be 8 to 31 percent larger in volume than the previous largest, the Ixtoc I oil spill, also in the Gulf of Mexico. Caused in the aftermath of a blowout and explosion on the Deepwater Horizon oil platform, the United States federal government estimated the total discharge at 4.9 MMbbl. After several failed efforts to contain the flow, the well was declared sealed on 19 September 2010. Reports in early 2012 indicated that the well site was still leaking. The Deepwater Horizon oil spill is regarded as one of the largest environmental disasters in world history.

<span class="mw-page-title-main">Corexit</span> Oil dispersant

Corexit is a product line of oil dispersants used during oil spill response operations. It is produced by Nalco Holding Company, an indirect subsidiary of Ecolab. Corexit was originally developed by the Standard Oil Company of New Jersey. Corexit is typically applied by aerial spraying or spraying from ships directly onto an oil slick. On contact with the dispersant, oil that would otherwise float on the surface of the water is emulsified into tiny droplets and sinks or remains suspended in the water. In theory this allows the oil to be more rapidly degraded by bacteria (bioremediation) and prevents it from accumulating on beaches and in marshes.

Dispersit SPC 1000 or Dispersit is a dispersant used for oil spills, produced by U.S. Polychemical Corporation.

Following is a Timeline of the Deepwater Horizon oil spill for May 2010.

Paint has four major components: pigments, binders, solvents, and additives. Pigments serve to give paint its color, texture, toughness, as well as determining if a paint is opaque or not. Common white pigments include titanium dioxide and zinc oxide. Binders are the film forming component of a paint as it dries and affects the durability, gloss, and flexibility of the coating. Polyurethanes, polyesters, and acrylics are all examples of common binders. The solvent is the medium in which all other components of the paint are dissolved and evaporates away as the paint dries and cures. The solvent also modifies the curing rate and viscosity of the paint in its liquid state. There are two types of paint: solvent-borne and water-borne paints. Solvent-borne paints use organic solvents as the primary vehicle carrying the solid components in a paint formulation, whereas water-borne paints use water as the continuous medium. The additives that are incorporated into paints are a wide range of things which impart important effects on the properties of the paint and the final coating. Common paint additives are catalysts, thickeners, stabilizers, emulsifiers, texturizers, biocides to fight bacterial growth, etc.

<span class="mw-page-title-main">Oil dispersant</span> Mixture of emulsifiers and solvents used to treat oil spills

An oil dispersant is a mixture of emulsifiers and solvents that helps break oil into small droplets following an oil spill. Small droplets are easier to disperse throughout a water volume, and small droplets may be more readily biodegraded by microbes in the water. Dispersant use involves a trade-off between exposing coastal life to surface oil and exposing aquatic life to dispersed oil. While submerging the oil with dispersant may lessen exposure to marine life on the surface, it increases exposure for animals dwelling underwater, who may be harmed by toxicity of both dispersed oil and dispersant. Although dispersant reduces the amount of oil that lands ashore, it may allow faster, deeper penetration of oil into coastal terrain, where it is not easily biodegraded.

Macroemulsions are dispersed liquid-liquid, thermodynamically unstable systems with particle sizes ranging from 1 to 100 μm, which, most often, do not form spontaneously. Macroemulsions scatter light effectively and therefore appear milky, because their droplets are greater than a wavelength of light. They are part of a larger family of emulsions along with miniemulsions. As with all emulsions, one phase serves as the dispersing agent. It is often called the continuous or outer phase. The remaining phase(s) are disperse or inner phase(s), because the liquid droplets are finely distributed amongst the larger continuous phase droplets. This type of emulsion is thermodynamically unstable, but can be stabilized for a period of time with applications of kinetic energy. Surfactants are used to reduce the interfacial tension between the two phases, and induce macroemulsion stability for a useful amount of time. Emulsions can be stabilized otherwise with polymers, solid particles or proteins.

<span class="mw-page-title-main">Gulf killifish</span> Species of fish

The Gulf killifish is one of the largest members of the genus Fundulus; it is capable of growing up to 7 inches (18 cm) in length, whereas the majority of other Fundulus reach a maximum length of 4 inches (10 cm). Therefore, F. grandis is among the largest minnows preyed upon by many sport fish, such as flounder, speckled trout, and red drum. Fundulus derives from the Latin meaning "bottom," and grandis means "large". The Gulf killifish is native to the Gulf of Mexico from Texas to Florida and the eastern coast of Florida and the Caribbean Sea in the Atlantic Ocean. Threats to the survival of the Gulf killifish include extreme changes in salinity, changes in temperatures, and toxic events such as the hypoxic dead zone in Louisiana and the Deepwater Horizon oil spill. The Gulf killifish is currently being used to test the effects of oil and oil dispersants on the physiology of marine species affected by these substances. This is significant to conservation biology, because with the continued extraction of oil and other natural resources from North American waters, it has become increasingly important to understand the risks and consequences in worst-case scenarios, such as the Deepwater Horizon oil spill, and the lasting effects on the marine ecosystem.

Health consequences of the <i>Deepwater Horizon</i> oil spill

The Health consequences of the Deepwater Horizon oil spill are health effects related to the explosion of the Deepwater Horizon offshore drilling rig in the Gulf of Mexico on April 20, 2010. An oil discharge continued for 84 days, resulting in the largest oil spill in the history of the petroleum industry, estimated at approximately 206 million gallons. The spill exposed thousands of area residents and cleanup workers to risks associated with oil fumes, particulate matter from Controlled burns, volatile organic compounds (VOCs), polycylic aromatic hydrocarbons (PAHs), and heavy metals.

<i>Deepwater Horizon</i> oil spill response Containment and cleanup efforts

The Deepwater Horizon oil spill occurred between 10 April and 19 September 2010 in the Gulf of Mexico. A variety of techniques were used to address fundamental strategies for addressing the spilled oil, which were: to contain oil on the surface, dispersal, and removal. While most of the oil drilled off Louisiana is a lighter crude, the leaking oil was of a heavier blend which contained asphalt-like substances. According to Ed Overton, who heads a federal chemical hazard assessment team for oil spills, this type of oil emulsifies well. Once it becomes emulsified, it no longer evaporates as quickly as regular oil, does not rinse off as easily, cannot be broken down by microbes as easily, and does not burn as well. "That type of mixture essentially removes all the best oil clean-up weapons", Overton said.

<span class="mw-page-title-main">GuLF Study</span>

The GuLF Study, or Gulf Long-term Follow-up Study, is a five-year research project examining the human-health consequences of the Deepwater Horizon oil spill in April 2010. The spill followed an explosion on a drilling rig leased by BP, the British oil company, and led to the release of over four million barrels of oil into the Gulf of Mexico, 48 miles off the coast of Louisiana in the United States.

References

  1. Pirrung, Frank O.H.; Quednau, Peter H.; Auschra, Clemens (2002). "Wetting and Dispersing Agents". CHIMIA International Journal for Chemistry. 56 (5): 170–176. doi: 10.2533/000942902777680496 .
  2. Superplasticizers Archived June 12, 2010, at the Wayback Machine . Fhwa.dot.gov. Retrieved on 2010-10-27.
  3. Gypsum wallboard, and method of making same - Patent 5879446. Freepatentsonline.com. Retrieved on 2010-10-27.
  4. 1 2 "Spill Response - Dispersants". International Tanker Operators Pollution Federation Limited. Archived from the original on 2013-11-14. Retrieved 2010-05-03.
  5. "Spill Response - Dispersants Kill Fish Eggs". Journal Environmental Toxicology and Chemistry. 10 April 2009. Retrieved 2010-05-21.
  6. Jernelöv, Arne; Lindén, Olof (1981). "Ixtoc I: A Case Study of the World's Largest Oil Spill". Ambio. 10 (6): 299–306. ISSN   0044-7447. JSTOR   4312725.
  7. The use of surface and subsea dispersants during the BP Deepwater Horizon oil spill (Working Paper). Washington, DC, USA: National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling. Published 2011. Available from: https://purl.fdlp.gov/GPO/gpo184