From Big Medical Encyclopedia

SORPTION (Latin sorbere to absorb, soak up) — absorption by solids and liquids of substances from the environment.

Villages widely use in a wedge, and medical biochemistry, during the receiving pharmaceuticals, during the cleaning of many foodstuff and waters, and also in biotechnology, pharmacology, chemistry. The Soviet scientists successfully improve sorption methods of purification of blood and a lymph — hemosorption (see t. 10, additional materials) and a limfosorbtion (see), applied for the purpose of a detoxication of an organism by elimination of toxins directly from blood and a lymph at a renal and liver failure, a serious poisoning and nek-ry other diseases.

In biol. systems the large role is played by S. of certain substances on surfaces of cells and various cellular organellas, on membranes and biopolymers. Binding of carbonic acid of a hloroplas-tama at photosynthesizing organisms, binding of oxygen erythrocytes, absorption in intestines, early stages of interaction of viruses with cells when a certain receptor on a surface of a virus interacts with a complementary receptor on a surface of sensory cells, fixation by immunocompetent cells (T - or V-lymphocytes) on the surface of erythrocytes (see Rosetting tests), bacteria, etc. can be examples of biological S. Effect of many medicines is based on absorption of substances, harmful to an organism, by them.

The phenomenon With, is explained by property of many solids and liquids possessing a certain stock of free superficial energy to aim to reduce this energy under existing conditions to the minimum values due to interaction with surrounding gases, couples or substances dissolved in liquids. It is accepted to designate the absorbing body the terms «sorbent» or «absorber», and the absorbed substance — «сорбтив» or «sorbate». Distinguish several types of S. depending on extent of participation in this process of an absorber and the mechanism of absorption. If absorption of substance from solution or mix of gases happens in all volume of an absorber, then this type of S. is called absorption (see), an absorber by absorbent, and the absorbed substance absorbtivy or absorbate. Distinguish a separate type of absorption — the occlusion representing absorption of substance from a gaseous fluid a firm or liquid sorbent. If absorption of substance or gas a solid or liquid is limited to a surface layer of a sorbent, process is called adsorption (see), an absorber adsorbent, and the adsorbed substance adsorbtivy or an adsorbate. The most widespread adsorbents in biol. and medical chemistry the silica gels, zeolites, active coals possessing thanks to considerable porosity very big absorption surface are. The surface falling on 1 g of a sorbent (in sq.m/g) — a so-called specific surface — is its important characteristic.

A special type of S. is the capillary condensation consisting in a condensation of the absorbed steam in liquid in a time and capillaries of firm sorbents. Capillary condensation plays an important role in a water relationships of soils.

Usually occluded substance enters weak not covalent interactions with a sorbent; at adsorption between adsorbent and an adsorbate hydrogen bindings are often formed (see the Molecule). The absorbed substance thanks to interaction with a sorbent can strongly be kept by it and therefore properties of the absorbed substances and connections can strongly differ from their properties in a stand-at-ease. So, the water molecules adsorbed by particles of the soil, fabrics and organellas biol. objects and biopolymers, are oriented in the adsorption layer thus that form a hydrated cover or a so-called bound water, properties a cut significantly differ from physical properties of usual water, (see). There is a special kind of S. when the absorbed substance enters chemical interaction with an absorber, i.e. so-called chemisorption. The page such can or be limited to a surface layer of substance (e.g., formation of films of oxides on the surface of nek-ry metals), or to extend to all volume of an absorber.

Different types of S. are characterized by different speeds. The largest saturating speed is inherent to adsorption as it is limited to a surface layer of substance, on speed capillary condensation is close to it. The smallest speed is observed at absorption, the cut is the limiting factor slow diffusion rate of molecules of the absorbed bulk material of an absorber. Therefore in liquid sorbents the absorption rate sharply increases during the hashing.

Most idiosyncrasy biol. The page is the selectivity determined by high degree of stereospecificity in interaction of many sorbents and sorbates possessing a certain complementary configuration. In this case certain sites of a macromolecular or supramolecular sorbent carry out a role of a receptor at absorption and binding of certain substances or even coarse particles.

Bibliography: Kireev V. A. Course of physical chemistry, page 500, M., 1975; V. K. Smiths and Ust-Kachki fl-ets in V. F. Physical and colloid chemistry, page 177, M., 1976.

T. I. Tikhonenko.