Surfactants are a special class of organic compounds whose amphiphilicity makes them prone to form various aggregates. Surfactants can reduce the interfacial tension between the two phases. Characteristic parameters include critical micelle concentration (cmc), hydrophilic-lipophilic balance (HLB), chemical structure, hydrophilic headgroup charge, etc. The surface activity of surfactants makes them excellent emulsifiers, dispersants and foaming agents. As active ingredients in soaps and detergents, surfactants (like sodium lauryl ether sulfate(SLES), alkylphenol ethoxylates (APE), and LABSA) are often used for cleaning purposes, separating oily substances from certain substrates.
Excellent Performances of Surfactants
Numerous reviews and scientific reports describe the wide range of applications of surfactant micelles in pharmaceuticals, detergents, cosmetics, coatings, food science, nanotechnology, optoelectronics, bioremediation, oil recovery, chemical reactions, and drug delivery.
Surfactants are widely used in industry as adhesives, flocculants, wetting agents, foaming agents, demulsifiers and penetrating agent. The petroleum industry has always had a great demand for surfactants, including for oil washing and tertiary oil recovery, demulsification, etc.
At present, with the growth of market demand and concern for environmental issues, as a substitute for chemical surfactants, a class of biodegradable surfactants derived from microorganisms has emerged, called biosurfactants. Biosurfactants have attracted extensive attention in the fields of medicine and industry because of their excellent physicochemical properties, harmlessness, biocompatibility, and chemical diversity.
The suitability of a particular surfactant for the reaction depends primarily on the nature of the aggregates formed. Aggregate structures of amphiphilic molecules are widely used in nanocatalytic reactors for organic reactions. In addition, surfactants have been successfully used to synthesize and stabilize metal nanoparticles. In most cases, monomeric surfactants participate in metal nanoparticle-catalyzed reactions in the form of aggregates, where metal nanoparticles are stabilized by amphiphiles, polymeric micelles, or dendrimers.
Applications of Surfactants in Various Fields
The use of surfactants in the global market has experienced steady growth over the past few years. The global surfactants market is in a transition phase: diversification or consolidation. The application of different types of surfactants in different fields is introduced as follows.
Cosmetics
The use of surfactants in pharmaceuticals has received intense attention over the past few decades. Surfactants have been studied as pharmaceutical excipients for many years due to their unique functional properties. Synthetic surfactants have been widely used in the petroleum, food and pharmaceutical industries as emulsifiers and wetting agents. Surfactants are used in the preparation of ointments, cold creams, cleansers, vanishing creams, and shaving creams so that they can be easily removed from the skin when washed with water. Many reviews, books and recently published articles have highlighted the use of surfactants.
Detergents and Cleaners
The role of detergents is primarily to clean the surface of a substance by removing hydrophobic oily molecules (such as non-covalently bound lipids) and dust particles, since water alone cannot remove greasy dirt from a cloth. Surfactants are usually used to remove these greasy soils from the cloth surface because surfactants can effectively solubilize these oily molecules by forming micelles.
Bioremediation
Bioremediation refers to the process of biological transformation of organic compounds by living microorganisms. It is a widely adopted new technology for waste treatment that can remove or neutralize environmental pollutants in contaminated sites. Compared with the earlier established chemical method, surfactant-assisted bioremediation technology is a more effective and convenient method for removing toxic heavy metals.
