Surfactant detergent and decontamination mechanism

Surfactant detergent and decontamination mechanism
Washing and decontamination is a very important application field of surfactants. Even in industrialized countries, surfactants used as various detergents still account for about 40% of the total production of surfactants. Detergency itself is a comprehensive process involving wetting, emulsification, foaming, dispersion, solubilization and other colloidal and interfacial chemical phenomena.

Overall, the process of detergent decontamination is quite complex, involving not only the colloid and interface chemistry centered on surfactants, but also mechanical and hydrodynamic effects, and the mechanism of the detergent decontamination process is still not very clear.
Simply put, detergent decontamination is the process of removing dirt from a solid surface immersed in a medium (usually water). In this process, the surfactant is usually adsorbed to the solid substrate and dirt surface, thus weakening the adhesion of dirt and solid surface, and then with the help of mechanical and water flow, so that the dirt from the solid surface separation and emulsification, dispersion, solubilization in the medium, removed by rinsing. In daily life often need to clean the solids are: clothing, tableware, tables, floors, bathrooms and human skin (bathing) and so on. Research has shown that regardless of the decontamination mechanism, the adsorption of surfactants on the substrate and dirt surface is the basis of the decontamination action. The basic process of detergent decontamination will be described, with emphasis on the effect of surfactant adsorption on the decontamination process.

Decontamination Mechanism
Basic decontamination process
Dirt is an extremely complex mixture, in terms of dirt on clothing, its sources are: ① human secretion (mainly sebum); ② atmospheric dust; ③ industrial and civil organic and inorganic pollutants. Dirt can usually be divided into two categories: liquid dirt and solid dirt. The former is dominated by a variety of grease, also known as oil, the latter is carbon black and a variety of inorganic substances. More often than not, liquid dirt and solid dirt are combined together, i.e. forming a mixture of oil and grease pollution with solid pigments. On the other hand the dirt on tables and cutlery is mainly liquid oils and protein-based dirt, and they are also found on children’s clothing.

Dirt adheres to solid surfaces by van der Waals gravitational and electrostatic forces. Washing involves weakening the adhesion and separating the two by the action of surfactants. The decontamination process can be expressed as:
Solid – dirt + detergent – solid – detergent + dirt – detergent
The whole process takes place in a medium (usually water). Under the action of the detergent, the dirt is separated from the solid surface and emulsified, solubilized, dispersed (suspended) in the medium and removed by rinsing.
The dirt removal process involves the following aspects: ① wetting of the solid surface and liquid dirt coiling; ② solubilization, emulsification and dispersion of dirt by surfactants; ③ formation of mixed phases (liquid/liquid, solid/liquid, gas/liquid dispersion system) and so on. In the washing process from the solid surface of the detached dirt may still be re-deposited on the solid surface, especially in the multi-cycle washing process. Therefore, the detergent must have good resistance to dirt redeposition.

Translated with DeepL.com (free version)