dialysis (rus. диализ) — removal of low-molecular impurities from colloidal systems and solutions of high-molecular compounds with use of semi-permeable membranes.

Description

The simplest device for dialysis, a dialyzer, is a pouch or sleeve made of semipermeable material, filled with the liquid to be purified and immersed in a solvent (a dispersion medium). Cylindrical vessels with a semipermeable membrane instead of a bottom are often used in place of a pouch. Diffusion processes are the basis of dialysis; therefore, it proceeds very slowly. Dialysis may be accelerated by increasing the ratio of the membrane area to the volume of the liquid to be dialyzed, by increasing the temperature, by agitation, by creating a pressure difference across the membrane.

Dialysis in an electric field (electrodialysis) accelerates the removal of electrolytes from dialyzed systems by dozens of times. A simple electrodialyzer consists of three chambers separated by membranes. The liquid to be purified is poured into the central chamber, and electrodes immersed in solvent are located in the side flow chambers. The ions in the stationary electrical field move directly to the corresponding electrodes, penetrating through the membrane from the central chamber into the side chambers. Multichamber electrodialyzers are used for higher performance.

Dialysis and electrodialysis are used in many industrial processes, in physicochemical and biological research, and in medicine. The method, which was called vivi-diffusion, was used in 1913 by the American scientist D. Abel to study the components of the blood of a living organism. The animal’s blood passed from an artery into a vein through colloidal tubes placed in a glass cylinder filled with physiologic solution. The Abel’s unit formed the basis for the design of the artificial kidney, which is used for hemodialysis.

Modern technologies allow producing dialysis membranes with a pore diameter of 20 nanometres. One examples of such a membrane is a track-etched membrane, obtained from interaction between a polymer film and ions accelerated in a charged particle accelerator.

Illustrations

Blood plasma filtration (plasmapheresis) machine Hemofenix-M, whose filtering elements are prod
Blood plasma filtration (plasmapheresis) machine Hemofenix-M, whose filtering elements are produced using track membranes with pores up to 100 nm in diameter.

Author

  • Zaitsev Dmitry D.

Source

  1. Dialysis // Great Soviet Encyclopedia 3 ed. (in Russian), 1969–1978. /http://bse.sci-lib.com/article027066.html (reference date 12.12.2011).

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