Several common methods for separation and purification of mixtures

Separation and purification of mixtures.

1.Physical methods.

1) Filtration: It is the solubility of each component of the mixture in the same solvent.

A method of separating insoluble solids from solutions. Such as the purification of coarse salt.

2) Evaporation concentration: It is a method used to separate solutes dissolved in solvents. Such as the separation of NaCl. in table salt solution

3) Crystallization and recrystallization.

It is a method to separate purified substances by using the solubility of each component in a mixture in a certain solvent with different temperatures. Such as the separation of NaCl and Kno3 mixtures. Recrystallization is actually a repeated operation of dissolution and crystallization.

4) Distillation and fractionation.

It is a method of separating substances by taking advantage of the properties of several miscible liquids with large differences in their respective boiling points. Such as the separation of various fractions from petroleum, and then the separation of C2H5OH and H2O mixtures.

Decanting: Separation of dense and insoluble solids from liquids.

Separation of sand and water.

Filtration: Separation of insoluble solids from liquids.

Purified drinking water.

Dissolution and filtration: Separation of two solids, one soluble in a solvent and the other insoluble.

Separate salt and sand.

Centrifugal separation: Separation of insoluble solids from liquids.

Separation of mud and water.

Crystallization: Separation of dissolved solutes from solution.

Extraction of table salt from seawater.

Dispensing: Separation of two immiscible liquids.

Separation of oil and water.

Extraction: The addition of an appropriate solvent to dissolve and separate a component of the mixture.

With heptane. Extraction of iodine from aqueous solutions.

Distillation: Separation of solvents and non-volatile solutes from solution.

Pure water is obtained from seawater.

Fractionation: Separation of two liquids that are miscible with large differences in boiling points.

separation of oxygen and nitrogen from liquid air;

Petroleum refining.

Sublimation: Separating two solids, only one of which can be sublimated.

Separation of iodine and sand.

Adsorption: Removal of gaseous or solid impurities from the mixture.

Activated charcoal is used to remove colored impurities from brown sugar.

Chromatography: Separation of solutes in solution.

Separation of different colored substances in black ink.

1.Fractional crystallization

This method is often used to heat the evaporation solution to control the density of the solution and crystallize a part of the solute. After repeated operations, the purpose of separation and purification can be achieved.

2.Step-by-step precipitation method

This method often selects appropriate reagents or adjusts pH to precipitate a certain part of the solution. After repeated operations, the purpose of separation and purification can also be achieved.

3.Selective redox method

Use a suitable oxidant or reducing agent to oxidize or reduce some components in the mixture, and further achieve the purpose of separation and purification.

4.Absorption, adsorption method

Absorb certain components of the mixture with suitable reagents, such as caustic soda to absorb carbon dioxide from the gas mixture. Or use suitable substances to adsorb some components in the mixture, such as adsorbing certain gases with activated carbon, so as to achieve the purpose of separation and purification.

5.Liquid-liquid solvent extraction

Select appropriate solvents to dissolve and absorb some components in the mixture, so as to achieve the purpose of separation and purification.

6.Distillation

The condensation temperature of the vapor of the mixed solution is controlled, so that the components with different boiling points are condensed and precipitated step by step, so as to achieve the purpose of separation and purification.

1.No new impurities can be introduced. That is, the substance after separation and purification should be pure, and no other substances can be mixed into it.

2.The state of the substance after separation and purification remains unchanged.

3.The experimental process and operation method are simple and easy. That is, the selection of separation and purification methods should follow the principle of physics before chemistry, simple before complex.

When iron and copper filings are mixed together, they can be separated by magnets.

When processing rice into rice in rural areas, sieves are often used to separate rice from bran;

Gauze bags are commonly used to separate tofu residue from soybean milk in rural areas;

When washing rice, the pouring method is often used to separate the washing water from the rice;

When there is more oil mixed in the water and stratified, the upper layer of oil can be gradually sucked out with a straw.

Sodium chloride and ammonium chloride are heated.

Extracted with aqua regia (cyanide)**.

Principles and requirements for separation and purification:

1) Principles to be followed in the selection of separation and purification methods.

No increase: Refers to the inability to introduce new impurities.

Undiminished: It means that the dust should be removed to reduce the loss of the separated and purified substances as much as possible.

Easy separation: It refers to the use of reagents to remove impurities, which requires that the product after the reaction is easy to separate from the purified substance.

Easy to recover: It means that the isolate or purified substance should be easily recovered.

2) The separation and purification operation process should follow the "three musts".

The impurity removal reagent must be excessive;

Excess reagents must be removed (because excess reagents will eliminate new impurities);

The best way to remove impurities must be selected.

The principle of substance separation and purification: two "no" and two "easy".

1) Do not increase [do not add new impurities].

2) Do not reduce [do not reduce the purified substance].

3) Easy to separate [easy separation of purified substances and impurities].

4) Easy to restore [the purified substance is easy to return to its original composition state].

1.Physical methods.

1) Filtration: It is a method to separate insoluble solids from solutions by using the difference in solubility of each component of the mixture in the same solvent. Such as the purification of coarse salt.

2) Evaporation concentration: It is a method used to separate the solute dissolved in the solvent. Such as the separation of NaCl. in table salt solution

3) Crystallization and recrystallization: It is a method to separate and purify substances by using the different properties of the solubility of each component in a mixture in a certain solvent with different temperature changes. Such as the separation of NaCl and Kno3 mixtures.

Recrystallization is actually a repeated operation to dissolve limbs and crystals.

4) Distillation and fractionation: It is a method of separating substances by using the properties of several miscible liquids with large differences in their respective boiling points. For example, the separation of the fractions of each rubber species from petroleum, and then the separation of C2H5OH and H2O mixtures.

Principles and requirements for separation and purification:

1) Principles to be followed in the selection of separation and purification methods.

No increase: Refers to the inability to introduce new impurities.

Undiminished: It means that the loss of the substances to be separated and purified should be reduced as much as possible.

Easy separation: It means that if the reagent is used to remove impurities, the product after the reaction is required to be easily separated from the purified substance.

Easy to recover: It means that the isolate or purified substance should be easily recovered.

2) The separation and purification operation process should follow the "three musts".

The impurity removal reagent must be excessive;

Excess reagents must be removed (because excess reagents can bring new impurities);

The best way to remove impurities must be selected.