surfactant

Surfactants are compounds that reduce the surface or interfacial tension between two phases, such as air and water or oil and water. They are typically amphiphilic, possessing both a hydrophobic tail and a hydrophilic head, which drives their adsorption at interfaces and their ability to modify wetting, spreading, emulsification, and dispersion. At low concentrations, surfactants align at interfaces; above a characteristic concentration called the critical micelle concentration, they self-assemble into micelles that solubilize hydrophobic substances and enable color and odor stabilization, among other effects.

Surfactants are commonly grouped by the charge of their hydrophilic head: anionic, cationic, nonionic, and zwitterionic. Examples include sodium dodecyl sulfate (anionic), cetyltrimethylammonium bromide (cationic), alkyl phenol ethoxylates (nonionic), and betaine-type surfactants (zwitterionic).

Applications include detergents and cleaners, cosmetics and personal care products, food additives (emulsifiers and thickening agents), pharmaceuticals, and industrial processes such as emulsification in paint, polymerization, and mineral flotation. They also serve in enhanced oil recovery and foaming or defoaming systems.

Manufacturing and formulation involve several routes, including sulfonation and alkoxylation. Some common classes are anionic sulfonates and sulfates, cationic ammonium salts, nonionic alkyl phenol ethoxylates, and zwitterionic betaines; ethoxylation or propoxylation tailors hydrophilic balance.

Safety and environmental considerations: Biodegradability and aquatic toxicity vary widely. Regulatory guidelines favor readily biodegradable surfactants and proper wastewater treatment to minimize ecological impact.