Working of Surfactants

Surfactants have a hydrophobic and hydrophilic nature. For this reason, they are categorized as amphiphilic. Surfactants diffuse in a compound and reduce the surface tension between that compound and another compound with which the original compound interacts. This is one of the common properties of surfactants and is utilized in soaps and detergents. The word surfactant was coined in and originates from the word surface-active agent. Some of the most common applications of surfactants include detergents, emulsifiers, foaming agents, etc. 

Working Of Surfactants

The main principle or mechanism behind the working of surfactants is a micelle formation. Surfactants have hydrophilic ends and hydrophobic ends. When immersed in water the hydrophilic end faces towards the water while the hydrophobic end faces towards the center of the structure. This kind of formation results in various shapes of micelles like spherical, cylindrical etc. The shape of the Micelle depends on the nature of the surfactant. When there is oil or dirt, the hydrophobic part of the structure gets attached to it. This dirt or oil is removed from the surface. Synthetic surfactants are formed when the magnesium /calcium ions of surfactants are replaced with other components. This is done to increase the efficiency of the surfactant. Magnesium or calcium ions in a surfactant produce useless scrum when used in hard water thus wasting resources. For this reason, those ions are replaced and based on what components the magnesium or calcium get replaced there are four kinds of surfactants – anionic, cationic, zwitterionic and nonionic.

Types Of Surfactants

1. Anionic surfactants – if the hydrophilic end of a surfactant carries a negative charge it is an anionic surfactant. Such surfactants when mixed with water produce anions that are negatively charged. These surfactants attach to positively charged particles in water. Thus, micelle is formed around the positively charged particle-like dirt and oil and they are removed from clothes or other surfaces. Examples of anionic surfactants include alkyl ether sulfate and phosphate esters. Their application includes detergents, soaps, body washes etc.

2. Cationic surfactants – if the hydrophilic end of a surfactant carries a positive charge it is a cationic surfactant. The specific use of cationic surfactant is that it can be used in an acidic environment. The positive nature of cationic surfactants is also able to break across cell membranes. This makes them useful in the production of antimicrobials. However, they have weaker cleaning power as compared to anionic surfactants. Examples of cationic surfactants include benzalkonium chloride and quaternary ammonium compounds. This type of surfactant is used in bacteriostats and fabric softeners.

3. Zwitterionic surfactants-These surfactants have two charges on the molecule, positive and negative. These surfactants improve the efficiency of other surfactants. They also reduce unwanted side effects of some surfactants like irritation of the skin, hair fall etc. These surfactants have an overall neutral charge. The positive ions of a zwitterion are mostly quaternized ammonium or phosphonium ions. Examples are erucyl amidopropyl betaine and lecithin.

4. Nonionic Surfactant –it is neutral in nature and does not have any charge on the hydrophilic end. This no-charge nature of it makes it useful in the production of emulsifying oils. A feature that makes this surfactant special is its cloud point. The temperature at which the surfactant and cleaning solution operates from each other is called cloud point. Nonionic surfactants are mild in nature. Some examples of such surfactants are ethoxylated alcohol and alkoxylated fatty acids. They are commonly used in the removal of grease dish soap etc.

Conclusion 

Surfactants are compounds that reduce surface tension between various compounds. Surfactants function on the basis of micelle formation. Based on their molecular structure there are four main types of surfactants. They are anionic,cationic,zwitterionic and nonionic. Surfactants are used in various products like fabric conditioners, detergents, antibacterial agents, shampoos etc. Surfactants also have harmful effects on the environment and humans in the long run. Surfactants have low biodegradability. This means that earthworms or other microorganisms can’t consume it and it does not get destroyed fast. Surfactants thus end up staying in the environment for a long period of time. Due to their toxic nature they lead to depleting aquatic life and microorganism during their presence in the environment.