Enrichment and drying technology series one.

1. Enrichment technology
concentrate from a low concentration solution to remove water or solvent into a high concentration solution.
chemical and
are often concentrated after extraction and before crystallization in the preparation process of chemical, biological and chemical products.
heating
and decompression evaporation are the most commonly used methods, and some separation purification methods can also play a concentrated role.
For example, ion exchange method and adsorption method so that the thin solution through the ion exchange column or adsorption column, the solution is adsorbed, and then with a small amount of excerption liquid thick excerption, division collection, can make the desired concentration of the substance increased several times to dozens of times. Ultrafiltration uses semi-permeable membrane to intercept the properties of large molecules, which is suitable for concentrating biological large molecules. In addition, the methods of precipitation agent, solvent extraction, affinity and layering can also achieve the purpose of concentration. Evaporation concentration is highlighted below.
evaporation is the process by which the water or solvent molecules on the surface of the solution obtain more dynamic energy than the attraction between the molecules in the solution and enter human space from the liquid surface. The solution can be concentrated by removing water or solvent from the solution by evaporation.
the following factors affect evaporation:
(1) heating increases the humidity of the solution, increases molecular momentum, and accelerates evaporation.
(2) to increase the evaporation area can increase the evaporation.
(3) pressure is inversely related to evaporation. Decompression evaporation is an ideal enrichment method. Decompression increases evaporation at low temperatures, thereby reducing the damage caused by heating to the substance.
(1) normal pressure evaporation
at normal pressure heating so that the solvent evaporation, and finally the solution is concentrated. The method of normal pressure evaporation is simple, but only suitable for concentrating heat-resistant substances and recovering solvents. A condensation tube should be installed between the
the receiver
condense the solvent's steam. The liquid container should be distilled with round bottom, the amount of liquid should not exceed 1/2 of the volume of the distillation bottle, so as not to boil when the solution mist droplets are taken away by steam or the solution flushed out of the distillation bottle.
a small amount of glass beads or broken magnets before heating so that the solution does not overheat and boil. Boiling can easily cause the liquid to burst out or cause the pressure inside the distillation bottle to increase sharply and break. When operating, first turn on the cooling water, avoid direct heating, to choose a suitable hot bath. The temperature of the hot bath is 20-30 degrees C higher than the solvent boiling point, the temperature is too high to make the evaporation speed too fast, the steam pressure in the distillation bottle exceeds the atmospheric pressure and then easily flushes the plug away, escapes a large amount of steam, and even makes the distillation bottle crack.
(2) decompression evaporation
is usually carried out at room temperature or low temperature. By reducing the pressure on the liquid surface of the concentrate, the boiling point is reduced, and the evaporation method is suitable for concentrating heat-volatile substances, especially biomolecules such as
proteins
, enzymes,
nucleic acids
and so on. When the container containing the concentrate is connected to the
surge pump
and the pressure is reduced, the evaporation rate of the solution surface increases with the increase of the vacuum, thus accelerating the evaporation and concentration of the liquid.
laboratory commonly used decompression concentrator for rotary evaporator, its operation is: first add the liquid sample to the round bottom
sam
container, the mouth of the bottle received a vacuum tube, the bottle body water bath heating; At first the decompression is slow, and when heated to a certain temperature, the solvent evaporates in large quantities. If there are too many bubbles, the valve should be opened immediately to reduce the vacuum.
2.
drying
technology
drying is the process of removing wet solids, pastes, concentrates and water or solvents from liquids. Water content of bio-chemical products can easily cause decomposition and degeneration, affecting quality. Drying improves the stability of the product, making it conform to specified standards for easy analysis, research, application and preservation.
according to the original aggregation state of water, drying can be divided into three ways: liquid is removed directly, drying from liquid and evaporation from solid state by bypassing liquid phase - sublimation. The last two generally require a certain amount of energy. Usually, according to the characteristics of energy supply, that is, according to the way of heating, drying is divided into contact, flow, radiation drying.
contact with drying, heat is transmitted to the material to be dried by heating the surface (metal plates, rollers), at which point moisture is evaporated into the air around the material. When the heat is flowing dry, the heat necessary for the drying process is transmitted by the gas drying medium, which takes the role of the heat carrier and medium, transferring moisture from the material to the surrounding medium. When radiation is dry, i.e. infrared dry, heat is transmitted from the radiation source in the form of electromagnetic waves, and the temperature of the radiation source is usually above 700 degrees C.
summary, the main factors affecting drying are:
(1) evaporation area:
evaporation area is large, conducive to drying, drying efficiency and evaporation area in direct ratio. If the thickness of the material increases, the evaporation area decreases, it is difficult to dry, which will cause the temperature to rise so that some of the materials block, moldy and bad.
.