Surface-active substances: general information
Surface-active substances - compounds,which affect the value of surface tension. In the process of interaction of liquid molecules between them, cohesive forces are formed. This force will be different in the surface and inner (deep) layers. Considering the state of the liquid, it is easy to establish that the particles that are directed into the system are surrounded from different sides by the same molecules that affect them. Equal to all forces that act on such a molecule, is equal to zero. Therefore, liquids have the smallest surface for a given volume. This clearly manifests itself in the spherical form of droplets. The presence of impurities of various compounds in liquids determines the magnitude of the surface tension.
The structure of SAW molecules
Particles of fatty acids and alcohols consist of twoparts that have different properties, so these compounds are very often called diphyper structures. One part of the molecule is represented by a hydrocarbon chain, and the other by different functional groups (amino group, hydroxyl, carboxyl, sulfo group). The longer the hydrocarbon chain, the more pronounced the hydrophobic properties of the particles, they will weaker interact with water.
Surfactants (surfactants)Organic origin: bile acids, proteins, soaps, alcohols, ketones, aldehydes, tannins, ketones, etc. Surface-inactive substances do not affect the surface tension (starch, glucose, fructose).
Non-ionic surfactants(NPC) are high-molecular bio-compounds that do not form ions in water. In water bodies, these substances come with industrial (chemical, textile, petroleum), household (using a variety of synthetic household detergents) and also sewage from agricultural land (herbicides, fungicides, insecticides, and folios in quality of emulsifiers).
Surface-active substances are foundvarious applications in the national economy. In the agricultural sector, they are used to prepare emulsions, as well as wettable powders in the practice of protecting plants against parasites. Research is being conducted on the use of surfactants in order to reduce the evaporation of moisture from the soil surface. If you pour soil with mixtures of such a composition, an ultrathin film forms on its surface, which prevents evaporation of moisture, but at the same time it perfectly passes air and atmospheric precipitation. If you treat fruits and vegetables with surfactant solution, they remain juicy and fresh for a long time. When surfactants are added to feeds, the weight gain of animals and birds increases by approximately 20% compared to the animals in the control group.
Surface-active substances: harm and benefit
Surface tension is of great importancefor processes of absorption of nutrients in the intestine. For example, fats, as well as lipids in the food tract, come in droplets. The latter are emulsified in the small intestine with the help of bile acids. Only after this, these fats are hydrolyzed by lipolytic enzymes. Very often, soap is added to the insecticides (surfactants). The manipulation allows insecticides to interact better with the insect body surface. However, surfactants have not only a positive, but also a negative impact on the body. For example, shampoo contains very harmful foaming agents (SAAs), such as sodium and ammonium lauryl sulfate, ammonium and sodium laureth sulfate. There is an opinion that these components have a carcinogenic effect.
