A dispersant or a dispersing agent is a substance, typically a

surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...

, that is added to a

suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspend ...

of solid or liquid particles in a liquid (such as a

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

emulsion An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...

) to improve the separation of the particles and to prevent their

settling Settling is the process by which particulates move towards the bottom of a liquid and form a sediment. Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a uniform manner in the direction e ...

or clumping. Dispersants are widely used to stabilize various industrial and artisanal products, such as

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

ferrofluid Ferrofluid is a liquid that is attracted to the poles of a magnet. It is a colloidal liquid made of nanoscale ferromagnetic or ferrimagnetic particles suspended in a carrier fluid (usually an organic solvent or water). Each magnetic particle ...

s, and

salad dressing A salad dressing is a sauce for salads. Used on virtually all '' leafy salads'', dressings may also be used in making salads of beans (such as three bean salad), noodle or pasta salads and antipasti, and forms of potato salad. Salad dressings ...

s. The

plasticizer A plasticizer ( UK: plasticiser) 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. Plasticiz ...

s or

superplasticizer Superplasticizers (SPs), also known as high range water reducers, are additives used in making high strength concrete. Plasticizers are chemical compounds that enable the production of concrete with approximately 15% less water content. Superplast ...

s, used to improve the workability of pastes like

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

and

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

, are typically dispersants. The concept also largely overlaps with that of

detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...

, used to bring oily contamination into water suspension, and of

emulsifier An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...

, used to create homogeneous mixtures of immiscible liquids like water and oil. Natural suspensions like

milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digestion, digest solid food. Immune factors and immune ...

and

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...

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 Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...

prevent the buildup of gummy residues.

Bio-dispersing

Dispersants are used to prevent formation of

biofouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that ...

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

s in industrial processes. It is also possible to disperse

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

l slime and increase the efficiency of

biocides A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US Environmental Protection Agency (EPA) uses a slig ...

Concrete and stucco

Dispersants are used as

s or

s in

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. Similarly, dispersants are used as plasticizers in the

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

slurry during

wallboard Drywall (also called plasterboard, dry lining, wallboard, sheet rock, gypsum board, buster board, custard board, and gypsum panel) is a panel made of calcium sulfate dihydrate (gypsum), with or without additives, typically extruded between thick ...

manufacture, to reduce the amount of water used. The lower water usage allows lower energy use to dry the wallboard.Gypsum wallboard, and method of making same - Patent 5879446
Freepatentsonline.com. Retrieved on 2010-10-27.

Detergents

Dispersing is the principal goal in the use of detergents, which the liquid bath is water (detergents also are used as

s in some applications). Laundry detergents encase dirt and grime in miscelles, which naturally disperse.

Oil drilling

Dispersants in

oil drilling An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may ...

aid in breaking up

solids Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ri ...

liquids A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...

as fine particles or

droplets A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant d ...

into another medium. This term is often applied incorrectly to clay

deflocculant Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from p ...

s. Clay dispersants prevent formation of "fish-eye" globules. For dispersing (emulsification) of

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

into

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

(or water into oils),

s selected on the basis of

hydrophilic-lipophilic balance The hydrophilic–lipophilic balance (HLB) of a surfactant is a measure of its degree of hydrophilicity or lipophilicity, determined by calculating percentages of molecular weights for the hydrophilic and lipohilic portions of the surfactant mo ...

(HLB) number can be used. For foam drilling fluids, synthetic

s and

soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...

s are used, along with

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

s, to disperse foam bubbles into the air or gas.

Oil spill

Dispersants can be used to dissipate

oil slick 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 th ...

s. They may rapidly disperse large amounts of certain oil types from the

sea surface The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

by transferring it into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

. They will cause the oil slick to break up and form water-soluble

micelle A micelle () or micella () (plural micelles or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension (also known as associated collo ...

s 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 emulsion An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...

s. However, laboratory experiments showed that dispersants increased toxic hydrocarbon levels in fish by a factor of up to 100 and may kill fish eggs. Dispersant was used in an attempt to clean up the

Exxon Valdez oil spill The ''Exxon Valdez'' oil spill occurred in Prince William Sound, Alaska, on March 24, 1989. ''Exxon Valdez'', an oil supertanker owned by Exxon Shipping Company bound for Long Beach, California struck Prince William Sound's Bligh Reef, west o ...

though its use was discontinued as there was not enough wave action to mix the dispersant with the oil in the water. Dispersant

Corexit Corexit (often styled 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 Compa ...

9500 was used on the

Deepwater Horizon oil spill The ''Deepwater Horizon'' oil spill (also referred to as the "BP oil spill") was an industrial disaster that began on 20 April 2010 off of the coast of the United States in the Gulf of Mexico on the BP-operated Macondo Prospect, considered ...

. Dispersant Corexit 9527 was used to disperse an oil slick in the Gulf of Mexico in 1979 ( Ixtoc), used over one thousand square miles of sea.

Process industry

In the

process industry Industrial processes are procedures involving chemical, physical, electrical or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy ind ...

dispersing agents are added to process liquids to prevent unwanted

deposits A deposit account is a bank account maintained by a financial institution in which a customer can deposit and withdraw money. Deposit accounts can be savings accounts, Transaction account#Current accounts, current accounts or any of several othe ...

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

coating A coating is a covering that is applied to the surface of an object, usually referred to as the Substrate (materials science), substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquid ...

s are inherently unstable, and they must be stabilized against the

flocculation Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from pr ...

that might occur.

References

{{Authority control Colloidal chemistry Fouling Process chemicals Oil spill remediation technologies Solvents Heterogeneous chemical mixtures