Surfactants are amphiphilic compounds, which results in the peculiar properties of these molecules, such as adsorption at interfaces, formation of micelles in solution and the decrease of surface tension. Industrial surfactants are a diverse group of chemicals with cleaning and/or solubilization properties. Generally, they consist of a polar head group (either charged or uncharged), which is well solvated in water, and a non-polar hydrocarbon tail, which is not easily dissolved in water.
Stabilisers: Industrial surfactants (being the mixtures of several individual compounds) can be used as stabilisers of emulsion liquid membranes (ELMs). The extraction and separation of organic compounds has become of a great interest in industrial process. Typically, substances produced in aqueous media have to be separated from impurities or by-products. From this point of view, emulsion liquid membranes (ELMs) turned out to be an effective and inexpensive method with potential application for this goal. Various types of substances have successfully been recovered by means of this technique, including organic acids, antibiotics and amino acids. However, as any technique, ELMs exhibits some drawbacks, such as membrane rupture, swelling and membrane instability. To ensure long-term stability and to avoid the membrane rupture, it is necessary to use a proper emulsion stabiliser. Such a substance reduces interfacial tension between water and oil phase, thus ensuring the formation of the stable emulsion droplets. Usually, this reduction is achieved by the application of surface-active compounds. A significant number of surfactants have been used for stabilisation of ELMs such as Paranox 100 or CR-500 for amino acid extraction.
Figure1. Surfactant used as stabilizer in reconfigurable microfluidic droplets
Textile dyeing: Industrial surfactants play an important role in the textile industry and the dyeing of textile is an obvious application. The added surfactants serve to support the uniform dispersion of the dyes in the dyeing media and proper penetration of the dyeing solution into the fibre matrix. Proper fixing of the dye on the surface enables uniform depth colouration of the textiles. Surfactants containing both hydrophilic and hydrophobic moieties play a useful role in textile processing by wetting the fibre surface quickly, uniformly and ideally in water medium. Further, these are used as leveling agents, dispersants and wetting agents in the dyeing process. The surfactants can form a complex with ionic dyes or they can facilitate the absorption of nonionic dyes. The interactions of the dyes with surfactants are of great importance for improving dyeing processes.
Figure 2. Surfactant properties in textile operations
Pharmaceutical: Industrial surfactant plays an important role in pharmaceutical production. The applications of surfactants are used in pharmaceutical manufacture, including the solubilization and emulsification functions. For example, lecithin is used as an emulsifier in pharmaceutical preparation and microemulsion is used as a kind of basic drug dosing system.