What Is a Colloid?

Colloid, also known as colloidal dispersion, is a relatively homogeneous mixture. The colloid contains two substances in different states, a dispersed phase and a continuous phase. A part of the dispersoid is composed of tiny particles or droplets. The dispersion system with a diameter of 1-100 nm is colloid; the colloid is a kind of dispersed particle with a diameter between the coarse dispersion system and the solution. A dispersion-like system, which is a highly dispersed heterogeneous heterogeneous system.

Divided into:

1. Agricultural production: the fertilizing effect of soil. Many substances in the soil, such as clay humus, often exist in the form of colloids.

2. Medical health: hemodialysis, serum

1.

Colloids are usually purified by dialysis. ^[3]

Dialysis is also called dialysis. Principle: The process of removing small molecules or ions as impurities from sols by using the properties of semi-permeable membranes that can penetrate small molecules and small ions but cannot penetrate colloidal particles. ^[5]

During the dialysis, the colloidal solution is placed in a dialysis machine composed of a semi-permeable membrane, and the dispersion medium (usually water) of the colloidal solution is periodically replaced outside the device to achieve the purpose of purifying the colloid. The application of a DC electric field during dialysis can often accelerate the diffusion of small ions from the inside of the membrane to the outside of the membrane, which is electrodialysis.

A method for separating particles of different solutes by using the selective permeability of a semi-permeable membrane. The dialysis of charged particles (such as ions, colloidal particles, etc.) in solution under the action of an electric field is called electrodialysis. Electrodialysis is widely used in chemical industry, light industry, metallurgy, papermaking, seawater desalination, environmental protection and other fields; in recent years, it has been more widely used in the purification and research of amino acids, proteins, serum and other biological products. There are many types of electrodialyzers, W. Bory's three-chamber type is representative, and its structure is shown in the figure. The electrodialyzer consists of three chambers: anode chamber, intermediate chamber and cathode chamber. The middle DD is a well-sealed semi-permeable membrane, E is a sheet or rod electrode such as Pt, Ag, Cu, etc., F is a glass tube connected to the middle chamber. For washing, S is a pH meter. Electrodialysis is essentially a desalination technique. The positive and negative ion exchange membranes in the electrodialyzer have selective permeability. A salt-containing solution is placed in the device. Under the action of direct current, the positive and negative ion membranes migrate to the anode and the anode, respectively. Finally, in the intermediate chamber between the two membranes, the salt concentration is reduced, and the anion and anode chambers are concentration chambers. The electrodialysis method can dilute, concentrate, separate or prepare certain electrolytic products from electrolyte solutes or certain substances. In practical applications, more than a hundred pairs of exchange membranes are usually used to improve the separation efficiency. During the electrodialysis process, factors such as the permeability of the ion-exchange membrane, the diffusion of ion concentration, the transmission of water, and polarization ionization will affect the separation efficiency.