The main difference between anionic surfactants and nonionic surfactants is that anionic surfactants have a negatively charged functional group, whereas nonionic surfactants have no net charge.
Surfactants are chemical substances that reduce the surface tension of a particular liquid when added to it. They increase the spreading and wetting properties. They are known as surface active agents. Surfactant molecules together form micelles, which are spherical in shape. Surfactant molecules contain a hydrophilic head and a hydrophobic tail. Moreover, we can group surfactants according to the properties of the functional groups present in the surfactant molecules. Anionic surfactants and nonionic surfactants are two such groups.
Key Areas Covered
1. What are Anionic Surfactants
– Definition, Nature, Features
2. What are Nonionic Surfactants
– Definition, Nature, Features
3. Difference Between Anionic and Nonionic Surfactants
– Comparison of Key Differences
Key Terms
Anionic Surfactants, Nonionic Surfactants, Surfactants
What are Anionic Surfactants
Anionic surfactants are surfactants that carry a negatively charged head in their molecules. This means their surfactant molecules have a negatively charged functional group as the head of the molecule. Examples of such functional groups are sulfates, carboxylates, phosphates, and sulfonates. In fact, anionic surfactants are the most popular surfactants. Some of the most popular anionic surfactants include sodium lauryl sulfate, ammonium lauryl sulfate, sodium laureth sulfate, ammonium laureth sulfate, potassium cocoate, and sodium stearate. Moreover, a wide range of oils and raw fats produce anionic surfactants.
Figure 1: Sodium Stearate
Anionic surfactants are mostly used to remove oily residue. They are commonly found in every cleaning agent. They are also used in body washes, kitchen cleaners, and laundry detergents. However, these anionic surfactants can also cause skin irritations.
Anionic surfactants create a lot of foam when mixed. The negative charge helps to lift and suspend soils in micelles. Anionic surfactants are used in many different industries because of their unique properties. Some of these include solubilization, emulsification, dispersion, foaming, detergency, and wetting.
What are Nonionic Surfactants
Nonionic surfactants are surfactants that have got no net charge. Nonionic surfactants are very soluble. This solubility is due to their hydrogen bonding. Hydrogen bonding decreases with an increase in temperature; therefore, the solubility of nonionic surfactants decreases with increasing temperature. When the temperature is increased, a milky, cloudy emulsion called a cloud point is formed. This property is important for the determination of the optimum use of nonionic surfactants at high temperatures. We apply this concept to detergents.
Figure 2: Surfactant Classification
Nonionic surfactants do not produce foam. They also do not contain dissociable ions. In other words, they do not separate into ions in water even though they contain a hydrophilic head and hydrophobic tail. They are available in a variety of chemical types. The main classes of nonionic surfactants are castor oil ethoxylates, amine ethoxylates, fatty acid esters and their ethoxylates, alcohol ethoxylates, and ethylene oxide propylene oxide copolymer. They are the second most used type of surfactant after anionic surfactants, but they are less effective than nonionic surfactants. Since they have no net charge on them, they are more stable than other surfactant types. Due to this feature, they are less susceptible to the effect of strong electrolyte inorganic salts, alkalis, and acids.
Difference Between Anionic and Nonionic Surfactants
Definition
Anionic surfactants are surfactants that carry a negatively charged head in their molecules, while nonionic surfactants are surfactants that have got no net charge on them.
Nature
Moreover, anionic surfactants are less mild in nature, whereas nonionic surfactants are comparatively milder than anionic surfactants. Generally, anionic surfactants are more effective than nonionic surfactants.
Foam Formation
Anionic surfactants produce a lot of foam, whereas nonionic surfactants do not produce foam.
Popularity
While anionic surfactants are the most popular surfactants in use, nonionic surfactants are the second most used type of surfactants.
Examples
Sodium lauryl sulfate, sodium laureth sulfate, ammonium lauryl sulfate, ammonium laureth sulfate, potassium cocoate, and sodium stearate are some popular anionic surfactants, while castor oil ethoxylates, amine ethoxylates, and fatty acid esters are examples of nonionic surfactants.
Conclusion
In brief, surfactants are chemicals that reduce the surface tension in liquids. They are of different types depending on the nature and structure of the molecule. Anionic and nonionic surfactants are two of the most common types of surfactants. The main difference between anionic surfactants and nonionic surfactants is that anionic surfactants have a negatively charged functional group, whereas nonionic surfactants have no net charge.
Reference:
1. “Anionic Surfactant – Overview.” Science Direct.
2. “Non-ionic Surfactants.” Stockmeier.
Image Courtesy:
1. “Sodium stearate” By User:Innerstream – Own work (Public Domain) via Commons Wikimedia
2. “TensideHyrophilHydrophob” By Roland.chem (CC BY-SA 3.0) via Commons Wikimedia
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