Muối tinh khiết natri clorua có nguồn gốc từ đâu? Các phương pháp sản xuất muối như thế nào?

Pure salt is a popular type of salt and extremely familiar to people. We use salt in every meal every day and it is also a common ingredient in many industries. How to create pure salt is probably something that many people wonder about. So in this article, hockinhdoanh.edu.vn will help you learn about salt, how to produce it and important applications of salt in practice.

Refer to 99% sodium chloride product here

1. What is pure salt Sodium Chloride (NaCl)?

Pure salt (also known as table salt, salt, sodium chloride, rock salt or halide) is a compound with the chemical formula NaCl. Sodium chloride mainly creates salinity in the oceans and extracellular fluids of many multicellular organisms.

Where does pure salt come from?

1.1. Origin of pure salt NaCl

NaCl salt partly comes from volcanic craters or rocks on the sea floor. However, the majority of salt originates on land.

Fresh water from rains is not 100% pure -> It dissolves CO2 in the atmosphere before falling to the ground -> Rainwater flows over the ground to reach drainage lines in the area -> Acidity of water Rain breaks down rocks, captures ions in rocks and carries them out to sea -> About 90% of these ions are sodium or chlorine -> These two types of ions combine to create salt.

1.2. Physical properties of pure salt

• NaCl salt is a colorless or white crystalline solid
• Melting point: 801 degrees Celsius, boiling point 1413 degrees Celsius, density 2.16g/cm3
• Solubility in water 35.9g/ml (25 degrees Celsius).
• Crystal structure: Each atom has 6 neighboring atoms creating an octahedral structure. This distribution is called closed cubic coupling.

NaCl is a colorless or white crystalline solid

1.3. Chemical properties of pure salt

• NaCl is a strong electrolyte, completely dissociating in water, creating positive and negative ions.
• Sodium Chloride is a salt of a fairly strong base and a strong acid so it is neutral -> therefore relatively chemically inert.
• Reaction with Ag+ salt (exchange reaction): NaCl + AgNO3 -> AgCl + NaNO3
• Reaction with water: Application to produce HCl.

2. So what is industrial pure salt used for?

2.1. In industry and production

Every year, about 200 million tons of pure salt are consumed for industry:

• People use salt to protect leather in the shoe and leather industry.
• Salt is also used to increase the whiteness of rubber.
• In the oil and gas industry, salt is an important ingredient in fluids used to drill oil wells.
• Pure salt is the starting material for making chemicals used in other industries such as copper, steel, aluminum, preparing Javel water,… by electrolysis of molten water, electrolysis of NaCl solution with a membrane.

Application of pure salt NaCl in industry and production

2.2. In agriculture and farming

• In livestock farming, people use salt to balance the physiological processes of livestock and poultry to help them grow quickly and reduce disease.
• Salt is used as a trace element mixed with organic fertilizers to help increase the effectiveness of fertilizers.
• People also use salt to classify seeds by weight.

2.3. Sodium Chloride in food

Sodium Chloride is an extremely important ingredient and is commonly used as a spice and food preservative:

• People use salt to marinate fresh foods such as fish, shrimp… to maintain freshness and avoid spoilage and rancidity before processing.
• NaCl has a clear effect in deodorizing food, as well as keeping fruits from turning brown.
• Controls the fermentation process and enhances food flavor.

Use salt to marinate fresh foods such as fish, shrimp… to maintain freshness

2.4. Sodium Chloride in medicine

• Pure salt is used to disinfect wounds, treat colds and to mix serum, antidotes and some other medicines to treat human diseases.
• It is an essential element for human life because the main components of salt are sodium and chlorine
• The two elements play an important role in balancing fluids in the body, ensuring cells function normally.
• Provides mineral salts for the body lacking water.
• Salt has the effect of detoxifying, purifying the body, beautifying the skin, treating sore throats, whitening teeth, curing bad breath,…

2.5. Pure salt in family life

• Pure salt is used to keep flowers fresh longer, clean cutting boards, and clean glassware.
• Helps clean refrigerators, greasy pans, irons, remove wine stains on clothes…
• Eliminates shoe odor, repels ants.
• Soaking clothes in cold water mixed with salt helps clothes last longer.

2.6. Application of Sodium Chloride in traffic

In cold countries, people use large amounts of salt to melt ice and snow on roads. With a concentration of 23.3% and the lowest temperature of -21.2 degrees Celsius, salt can melt ice. The best temperature for salt to melt ice is 0 degrees Celsius.

In the US, nearly 40% of salt production is used for this work.

Use pure salt to melt ice on roads

3. How to produce quality NaCl pure salt?

3.1. In the laboratory

• Acid reacts with base

HCl + NaOH → NaCl + H20

Na2Cr2O7 + 14HCl→ 2NaCl + 2CrCl3 + 3Cl2 + 7H20

• Bubble chlorine gas into the alkaline solution

2NaOH (cold, dilute) + Cl2 → NaCl + NaClO + H20

5NaOH (hot) + 3Cl2 → NaClO3 + 3H20 + 5NaCl

• Chlorine repels bromine and iodine from bromide and iodide salts

2NaBr + Cl2→ 2NaCl + Br2

2NaI + Cl2 → 2NaCl + I2

• Hydrolysis of oxygen-containing compounds that are unstable to heat such as NaClO3

2NaClO3 (MnO2 catalyst, heating) → 2NaCl + 3O2

• Gently heat the saturated mixture of NH4Cl and NaNO2

3.2. In industry

Method for producing pure salt

3.2.1 Extraction from sea water

Today, people mainly produce table salt (NaCl) by concentrating a solution containing NaCl. Seawater is the most common solution containing NaCl. Therefore, the main method for producing table salt in our country is seawater concentration. Because of that, many Vietnamese people still call table salt sea salt.

Sea salt produced in different regions has different crystal colors due to differences in sea water composition and soil conditions.

3.2.2. Production of sea salt by surface evaporation method

• Production of sea salt by sand drying method:

Sand has a large specific area, taking advantage of this property of sand, people have used sand to increase the open surface area of ​​sea water so that a large amount of fresh water evaporates when producing table salt from sea water. Therefore, in the production of sea salt by sand drying method, sand is called a medium for evaporation.

To get sea water to produce salt, sand-drying salt fields often take advantage of the tidal height to get self-flowing water through the welcome gate, also known as the tide gate.

When seawater evaporates fresh water through drying sand (a process carried out in a field, also known as a sand drying yard), seawater gradually increases in concentration, until the concentration of seawater in the drying sand layer reaches a state of saturated and then supersaturated with NaCl, the salt is separated in solid form and adheres to the sand grains (people call this process the process of salt agglomeration on drying sand).

The crystallization process when producing sea salt using the sand drying method only takes place within one day (in the morning, the water is put out to dry in the crystallization box, in the evening the salt is collected).

Producing sea salt by sand drying method usually produces sea salt products with a NaCl content of about 80% by volume. Producing sea salt by sand drying method in our country has low yield and quality of sea salt products (only used for daily life requirements). This method retains almost all the substances and trace compounds contained in the original seawater composition.

Production of pure salt by sand drying method

• Production of sea salt by water drying method:

In fact, there are many areas where natural freshwater evaporation conditions are favorable and stable for a long time. In these areas, to produce sea salt, people just need to expose sea water to dry in treated fields. on the water permeability of field plots.

The process of drying seawater in the field will gradually increase the concentration of seawater (NaCl content gradually increases). Sea water gradually reaches a saturated state and then when it is too saturated, the salt is separated in solid form.

First, the salt crystal seeds are formed from supersaturated water, then the salt crystal seeds gradually grow larger as the drying process continues, so the salt crystals are formed from the salt crystal seeds that gradually grow larger. to maturity.

Many salt crystals are formed to create a salt layer. The thickness of the salt layer depends on how long or short the salt crystallization time is (long or short salt crystallization cycle).

Production of table salt by water drying method

3.2.3. Production of pure salt by forced evaporation method

• Open pot concentration method

Put water that is nearly saturated or saturated with NaCl salt into a salt cooking pot. In Vietnam, these pots are usually made of corrugated iron, then use charcoal to heat and evaporate the fresh water.

The advantage of this method is that it can create many types of salt products, solve the problem of poor quality salt, does not require high technology and helps salt makers easily be proactive in salt production.

However, this method uses coal to burn, so it is expensive, pushing up salt prices while the salt yield is low. Using coal as fuel also causes negative effects on the environment, especially the air environment.

• Vacuum evaporation method

Put water that is nearly saturated or saturated with NaCl into the salt cooker, and use saturated steam to provide energy to evaporate the fresh water.

This method also creates many different types of salt of good quality and increases autonomy in production. However, this production requires high technical requirements and consumes artificial energy such as saturated steam, so the price is quite high and the salt output produced is not high.

3.2.4. Electrodialysis method

In the electrodialysis tank, negative and positive ion exchange membranes with high selectivity for Na+ and Cl- are installed alternately. Under the effect of this exchange membrane, when the electrodialysis tank works, high concentration salt water and fresh water will be separated into two separate compartments.

3.3. Mining rock salt

The 250-year-old salt mine under the sea is mesmerizingly beautiful

Conduct deep drilling into the ground, where a significant salt reservoir is discovered, 1-2m away, then pump water into the drill hole to extract the salt reservoir, and organize a road to collect water with high salinity. Concentrate this water to collect salt.

3.4. Refining sodium chloride salt

Salt created from the above methods contains many mechanical and chemical impurities. To obtain a cleaner NaCl product, it is necessary to refine it again.

4. Where to buy NaCl pure salt to ensure reputation and quality?

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