1. Foundry Industry

Bentonite for casting is a major user of bentonite, with an annual consumption of 1.1 million tons.

 

Bentonite is mainly used in clay bonded sand for casting, as it has characteristics such as strong adhesion, high plasticity, good detachment, excellent permeability, and stable physical and chemical properties under high temperature and wet conditions. The production of castings using clay bonded sand as a molding material is a long-standing process method. In today's booming development of various chemical bonded sand, clay wet molding sand is still an important molding material. Its wide range of application and high consumption are incomparable to any other molding material.

 

Modern new technologies such as high-pressure molding, injection molding, air impact molding, static pressure molding, and shock free vacuum pressure molding are all based on the use of clay green sand, which has a strong ability to adapt to molding conditions. There are two main types of bentonite used in casting: sodium bentonite and calcium sodium bentonite. Sodium bentonite is processed from natural sodium bentonite or artificial sodium bentonite, and is popular in the casting industry due to its good reusability and high wet compression strength.

 

Due to its good plasticity, it can prevent sand inclusion, scarring, chipping, and sand mold collapse in castings. In addition, it has strong formability and high cavity strength, making it easy for the metal industry to cast wet or dry molds. It is an optional sand binder for castings. Calcium sodium bentonite is processed from natural calcium sodium bentonite and is a commonly used molding sand binder for lightweight castings. It is popular among users for its practicality and convenient sand cleaning of castings.

 

Compared with other binders, bentonite has an important characteristic that it has a certain degree of heat resistance. As long as the heating temperature is not too high, bentonite with free water removed can still restore its adhesion ability as long as water is added. The bonding ability of bentonite can only be demonstrated after adding water. The loss of bonding ability of bentonite is also related to its dehydration. So far, it is believed that the water in the bentonite has three forms: one is free water, that is, the water adsorbed by the bentonite particles. When heated to more than 100 ℃, free water can be removed, and the bentonite with free water removed will not affect the bonding ability; The two types of water are firmly bound water. When heated for a long time at 110 ℃, bentonite can completely remove free water, but it will not remove firmly bound water.

 

Bentonite that has completely removed free water and is heated at higher temperatures (such as 200 ℃, 300 ℃) will continue to lose weight, indicating that there is still water loss. After being heated and dehydrated in this way, bentonite can fully restore its bonding ability by adding water; The three types of water are lattice water, also known as structural water. Lattice water can only be partially or completely removed at a relatively high temperature. After the lattice water of bentonite is removed, it loses its bonding ability and becomes dead clay.

 

The temperature at which different bentonite loses its bonding ability varies. According to Differential thermal analysis experiment, generally speaking, the failure temperature of natural sodium bentonite is 638 ℃, and that of calcium bentonite is 316 ℃. Artificial activated sodium bentonite has different activation conditions and failure temperatures, but they are all lower than natural sodium bentonite.

 

2 drilling mud

Bentonite for drilling mud is the second largest user of bentonite, with an annual consumption of 700000 tons.

 

Bentonite is a kind of clay mineral with Montmorillonite as the main component. It has strong water absorption and can absorb water equivalent to 8 times of its own volume. The volume expansion is 10~30 times. It is suspended and gelled in aqueous solution. When conducting oil and gas drilling and other tasks, mud should be used to cool the drill bit, remove debris, protect the wellbore, and balance ground pressure. Bentonite has good dispersibility and large slurry output, making it an ideal material for manufacturing drilling mud.

 

The important technical requirements for bentonite used as drilling mud are suspension properties, wet sieve analysis, and moisture content.

 

The important role of bentonite in drilling makes its usage very large. It is understood that on average, about 8 tons of bentonite are used for each well being mined.

　

3 Iron ore pellets

Bentonite used in iron ore pellets is the third largest user of bentonite, with an annual consumption of 450000 tons.

 

Bentonite used in iron ore pellets is one of the important additives in modern metallurgical industry. Concentrated iron powder is mixed with an appropriate amount of bentonite and water, and then rolled into a ball shape in a pelletizer. It is then dried, preheated, and roasted to form high-strength pellets for smelting.

 

4. Active clay and granular clay

Activated clay is a chemical product processed from bentonite, which has various functions of activated carbon and is much cheaper than activated carbon.

 

Therefore, various mineral oils widely used in the petroleum industry, animal and vegetable oils in the oil and fat industry, solid and liquid paraffin, fatty acids, waste oil regeneration, ethanol and benzene decolorization and refining. It can also be used for clarification of wine and juice, purification of sugar juice in the sugar industry, catalyst carrier in the chemical industry, and addition of powder pesticides.

 

There are about 40 manufacturers of activated clay in China, with an annual output of approximately 420000 tons.

 

The larger production unit has a capacity of 50000 t/a. The production areas of activated clay are mainly concentrated in Northeast, North China, East China, and other regions, accounting for over 70% of the country's production. At present, the demand for activated clay in China is about 650000 tons/a, and approximately 40000 tons are imported annually.

 

Granular white clay is made of activated white clay as the main raw material, through scientific formula and chemical treatment. Its appearance is amorphous small particles. It has higher specific surface area and particle strength than activated white clay, stable performance, good selectivity, and high adsorption capacity. It is widely used in the petrochemical industry for aromatics purification, Jet fuel refining, and also used in the refining of lubricating oil, base oil, diesel oil and other oil products to remove residual olefins Impurities such as gum, asphalt, alkaline nitrides, etc.

 

At present, domestic granular clay is mainly used to replace American TONSIL granular clay for olefin removal in aromatics complex, Jet fuel, solvent oil refining, pure benzene refining, which can remove a small amount of nitrogen compounds, resins, pigments, etc. Granular clay is sometimes called oil filter silica gel. The use of oil filter silica gel can effectively remove acids, oil sludge, bio colloids, and insulating materials. It can also remove water, impurities, and chromatographic analysis of hydrocarbon gases. It can be used for sewage treatment, filtration of toxic gases, and catalytic cracking in the petrochemical oil industry.

 

5 Desiccants

Bentonite desiccants have adsorption activity, static dehumidification, and odor removal effects. It is widely used for dry air storage of Optical instrument, electronic products, medical care, food packaging, military products and civilian products in products that cannot be sealed by oil seal and vapor phase. Compared with silica gel, it has the advantages of low price, fast adsorption speed, and low preparation cost.

 

Compared with other types of desiccants currently available on the market, it not only has fast adsorption speed, high adsorption capacity, and is non-toxic, odorless, non corrosive, and environmentally friendly, but also is particularly suitable for food packaging and has no harm to human health.

 

The export volume of bentonite desiccant is relatively large.

 

6 cat litter (granular bentonite)

Cat litter (granular bentonite) is made from natural bentonite and is refined through high-temperature drying. It has a white and beautiful color, strong adsorption, and small specific gravity. It is durable and suitable for household pet cleaning and hygiene.

 

Cat litter (granular bentonite) has a large export volume.

 

7 Sewage treatment

Using bentonite as animal gasket material to treat wastewater and odor can make animal feces easy to disperse and clean. Due to the harmful effects of sewage and odor generated by captive animal farms, slaughterhouses, and aquatic processing plants on the environment, bentonite can be scattered in these places to recover fertilizers.

 

Bentonite can be used as a clarifier for turbid water, a waterproof agent for polluted water, and a sewage treatment agent. Bentonite is used to treat printing and dyeing wastewater, gas washing wastewater, monosodium glutamate factory and other wastewater and wastes, with a removal rate of 99. 5%. Spreading bentonite upstream of the reservoir can cause unclean substances to flocculate and settle at the bottom of the reservoir for biological purification and treatment.

 

8 Construction Engineering

Utilizing the lubricity, bonding sealing, thickening, and cementitious properties of bentonite to make slurry, it is used for lining wall anti-seepage in various soil operations, such as partition wall construction, grouting, caisson, pile driving, soil anti-seepage, cement and concrete construction additives, solid water transportation, sewage treatment, and tunnel shield lubrication.

 

Paving the river with a bentonite impermeable layer can divert limited water to distant areas. The waterproof layer of bentonite can be directly laid with natural sodium based bentonite powder, or it can be mixed and compacted with local soil. Bentonite can also be sandwiched between two layers of fabric to form a waterproof (permeable) blanket (board), which can quickly build water storage tanks, water storage kilns, and water conveyance channels.

 

Bentonite can be used as a waterproof material, such as corrugated cardboard filled with bentonite as a waterproof board, two layers of non-woven fabric with bentonite sandwiched between them as a waterproof felt, and one layer of non-woven fabric and one layer of plastic board with bentonite sandwiched between them as a double waterproof board. This material has been widely used in underground projects such as subways, dam bottoms, and landfill sites.

 

Bentonite has a high degree of water tightness and self repair and restoration function, and its waterproofing has compactness (sodium bentonite forms a diaphragm under water pressure, with a thickness of about 5mm, which is equivalent to 100 times the compactness of 30cm thick clay) Good water retention performance (when sodium bentonite reacts with water, it has an expansion force of 3-6 times, which can repair cracks on the surface of concrete within 2mm) and waterproof performance (sodium bentonite will not age or corrode).

 

Bentonite is harmless to the human body and has environmental protection properties. Easy construction. No heating or pasting required, unaffected by temperature. At the same time, the construction period is short, and compared to other waterproof materials, the construction is relatively soft and simple. Use only nails and washers. After construction, there is no need for special inspection, and if waterproof defects are found, they are also easy to repair.

 

9 Food

As a food additive and emulsifier in food, it can be used as a calcium supplement and weight loss food.

 

Bentonite can clarify fruit juice and sugar juice. Bentonite can soften Water softening. Bentonite is used to clarify wine by fixing nitrogen without precipitation, reducing the formation of acetaldehyde and hydrogen sulfide, and eliminating all foreign odors.

 

10 Coatings

Bentonite is used as a multifunctional white coating in the papermaking industry. It also acts as an anti pitch adsorbent in pulps, a retention agent in machinery, and a rheological regulator in pulp.

 

Bentonite can also be used to produce coatings. As a viscosity regulator and white mineral filler in coatings, it can partially or completely replace titanium dioxide powder; It can also partially replace polyvinyl alcohol and be used as a binder for non-woven fabrics and gypsum board particles.

 

Bentonite can modify oxidized starch adhesive, which not only increases the solid content of the adhesive, reduces water content, but also blocks and fills the gaps in paper fibers (especially straw pulp paper), reduces water permeability, and thus improves the initial adhesion and drying speed of the adhesive.

 

Experiments have shown that bentonite has good effects and low prices, making it an ideal fast drying agent.