What Is Bentonite?

Bentonite is a non-metallic mineral with montmorillonite as the main mineral component. The montmorillonite structure is a 2: 1 type crystal structure composed of two silicon-oxygen tetrahedrons sandwiched with a layer of aluminum-oxygen octahedron. There are certain cations such as Cu, Mg, Na, K, etc. in these layered structures, and the interaction between these cations and the montmorillonite unit cell is very unstable, and it is easy to be exchanged by other cations, so it has good ion exchangeability. It has been applied in more than 100 departments in 24 fields of industrial and agricultural production abroad, with more than 300 products, so people call it "universal soil".

Bentonite is also called bentonite, bentonite or bentonite. China has a long history of developing and using bentonite. It turned out to be a detergent. (Since the open-pit mine in Renshou, Sichuan, hundreds of years ago, the locals call it bentonite). It is really widely used but only a hundred years old. The earliest discovery in the United States is that in the ancient formations of Wyoming, the yellow-green clay was able to swell into a paste after adding water. Later, people called this clay as a bentonite. In fact, the main mineral component of bentonite is montmorillonite, whose content is 85-90%. Some properties of bentonite are also determined by montmorillonite. Montmorillonite can be in various colors such as yellow-green, yellow-white, gray, white and so on. It can be compact or loose soil. It has a slippery feel when rubbed with fingers. The volume of the small block swells several times to 20-30 times after adding water. It is suspended in water and paste when there is little water. . The nature of montmorillonite is related to its chemical composition and internal structure.

Foreign name: bentonite
Alias: Bentonite bentonite
CAS number: 1302-78-9

Density: 2 ~ 3g / cm3
Boiling point: 381.8 ° C at 760 mmHg
Flash point: 184.7 ° C

Bentonite classification

When the interlayer cation is Na +, it is called sodium-based bentonite; when the interlayer cation is Ca2 +, it is called calcium-based bentonite; when the interlayer cation is H +, it is called hydrogen-based bentonite (active clay, natural bleaching clay-acid white clay); When called organic bentonite.

Activated white clay

Activated clay is an adsorbent made of clay (mainly bentonite) as raw material, treated with inorganic acid, rinsed with water, and dried. The appearance is milky white powder, odorless, odorless, non-toxic, strong adsorption performance, can adsorb Colored substances, organic substances. It is easy to absorb moisture in the air. If it is left for a long time, it will reduce the adsorption performance. However, when it is heated above 300 degrees Celsius, it starts to lose crystal water, which changes the structure and affects the fading effect. Activated clay is insoluble in water, organic solvents and various oils. It is almost completely soluble in hot caustic soda and hydrochloric acid. Its relative density is 2.3 to 2.5, and it has very little swelling in water and oil.

Natural bleaching earth

That is, the white clay that is naturally produced and has bleaching properties is white, white-gray clay with montmorillonite, sodalite, and quartz as the main components. It is a kind of bentonite.

It is mainly the product of the decomposition of glassy volcanic rocks. It does not swell after absorbing water. The pH value of the suspension is different from weakly acidic and alkaline bentonite; its bleaching performance is worse than that of activated clay. Colors are generally light yellow, green and white, gray, turquoise, brown, milky white, pink, and blue. Pure white rarely. The density is 2.7-2. 9g / cm. Apparent density is often lower due to porosity. The chemical composition is similar to that of ordinary clay. The main chemical composition is alumina, silica, water, and a small amount of iron, magnesium, and calcium. No plasticity and high adsorption. Because it contains a lot of hydrous silicic acid, it is acidic to litmus. It is easy to crack in water and has a large water content. Generally, the finer the detail, the higher the decoloring power.

During the quality evaluation in the exploration stage, it is necessary to determine its bleaching performance, acidity, filtration performance, oil absorption and other items ^[1]

Organic bentonite

Organic bentonite is an inorganic mineral / organic ammonium complex. It uses bentonite as a raw material and uses the lamellar structure of montmorillonite in bentonite and its characteristics of being able to swell and disperse into colloidal clay particles in water or organic solvents. Technology made by inserting an organic covering agent. Organic bentonite can form gels in various organic solvents, oils, and liquid resins. It has good thickening, thixotropic, suspension stability, high temperature stability, lubricity, film formation, water resistance and chemical stability. It has important application value in the coating industry. It is also widely used in paint and ink, aviation, metallurgy, chemical fiber, petroleum and other industries.

Bentonite

Bentonite ore is a multi-purpose mineral. Its quality and application field mainly depend on the content and type of montmorillonite and its chemical properties. Therefore, its development and utilization must be different for different mines and for different functions. Such as the production of activated clay, calcium-based to sodium-based drilling drilling grouting for oil drilling, instead of starch for spinning, printing and dyeing slurry, building materials with internal and external wall coatings, preparation of organic bentonite, synthesis of 4A zeolite with bentonite, production Silica and more.

Difference between calcium and sodium

The type of bentonite cations determines the type of bentonite. When the interlayer cation is Na +, it is called sodium bentonite; when the interlayer cation is Ca +, it is called calcium-based bentonite. Sodium montmorillonite (or sodium bentonite) has better properties than calcium . However, calcareous soils are far more widely distributed in the world than sodium soils. Therefore, in addition to strengthening the search for sodium soils, it is necessary to modify calcareous soils to make them into sodium soils. ^[2]

Bentonite properties

Brief Introduction of Bentonite

Bentonite is a kind of clay rock, also known as montmorillonite clay rock.

Bentonite Contains a small amount of illite, kaolinite, halloysite, chlorite, zeolite, quartz, feldspar, calcite, etc .; generally white, light yellow, light gray, light green, pink, brown due to changes in iron content Red, brick red, gray-black, etc .; waxy, earthy or greasy; some of the bentonite are loose like soil, and some are dense and hard. The main chemical components are silica, alumina, and water, and it also contains elements such as iron, magnesium, calcium, sodium, and potassium. The content of Na2O and CaO has a significant impact on the physical and chemical properties and process performance of bentonite. Montmorillonite minerals are monoclinic, usually soil-like blocks, white, sometimes with light red, light green, light yellow and other colors. The gloss is dull. The hardness is 1 to 2, and the density is 2 to 3 g / cm3. According to the type, content and interlayer charge of the montmorillonite exchangeable cations, bentonite can be divided into sodium-based bentonite (alkaline soil), calcium-based bentonite (alkaline soil), natural bleaching soil (acid soil or acid white clay) Among them, calcium-based bentonite includes calcium-sodium and calcium-magnesium. Bentonite has strong hygroscopicity and swellability. It can absorb 8 to 15 times its own volume of water, and its volume expansion can reach several times to 30 times. It can be dispersed into gel and suspension in aqueous medium. This medium solution It has a certain viscosity, thixotropy and lubricity; it has strong cation exchange capacity; it has a certain adsorption capacity for various gases, liquids and organic substances, and the maximum adsorption capacity can reach 5 times its own weight; Blends of water, mud or fine sand have plasticity and cohesiveness; surface-active acid bleaching clay (active clay, natural bleaching clay-acid clay) can adsorb colored ions.

Bentonite adsorption

Adsorption is a natural phenomenon in which all solid matter is present. The phenomenon that we gather certain molecules on the surface of bentonite is called the adsorption of bentonite. This adsorption has been widely used in industry. For example, drilling mud often uses the adsorption characteristics of bentonite minerals to adjust mud parameters for different purposes. For example, when adding fluid loss reducer, one end of the polymer is adsorbed on the surface of the bentonite particles, and the other end is dissolved in water to make the bentonite particles and water molecules. There is an indirect connection. A bridging effect is formed, which reduces the free water in the mud, changes the performance parameters of the mud, and reduces the filtration loss rate.

Bentonite adsorption can be divided into three types: physical adsorption, chemical adsorption and ion exchange adsorption.

l) Physical adsorption. Physical adsorption is produced by the intermolecular attraction between the adsorbent and the adsorbate, which is often referred to as the van der Waals force. Physical adsorption is a reversible adsorption process, and the adsorption speed and desorption speed show dynamic equilibrium under certain conditions. The main reason for the physical adsorption is that the surface molecules of bentonite have surface energy. Due to the high dispersion of bentonite in water, the phenomenon of physical adsorption is very obvious.

2) Chemical adsorption. Chemisorption is generated by the chemical bonding force between the adsorbent and the adsorbate. Chemisorption is generally irreversible. The application of chemical treatment agents in drilling mud is a typical example of chemisorption. For example, the addition of iron chromium lignin sulfonate to bentonite mud is the integrated adsorption of chromium ions on the edges of bentonite crystals. This chemisorption is significantly more stable than physisorption. Therefore, the bentonite mud treated with iron chromium lignin sulfonate has higher temperature resistance and can be used as a high temperature resistant mud system for geothermal and ultra-deep wells.

3) Ion exchange adsorption. Bentonite mineral crystals are generally negatively charged, so the equivalent of oppositely charged cations must be adsorbed on the surface of the bentonite particles. The adsorbed cations can exchange with the cations in solution. This effect is called ion exchange adsorption. The characteristics of ion exchange adsorption are: exchange of ions of the same number with each other, and exchange of isoelectricity. The reaction of ion exchange adsorption is reversible. The speed of adsorption and desorption is affected by the ion concentration, and this effect conforms to the law of mass action.

The factors affecting the adsorption of bentonite minerals are:

1) The effect of bentonite type. The adsorption capacity of sodium bentonite is obviously stronger than that of other types of bentonite minerals such as calcium.

2) The effect of the particle size of the bentonite particles. According to the theory of solid adsorption, the adsorption capacity of pulverized bentonite minerals is significantly improved. The finer the pulverized minerals, the stronger the adsorption effect.

3) The influence of solution medium. According to the electric double layer theory, bentonite mineral crystals are negatively charged, and ion exchange occurs when the electric double layer is formed. If the ion concentration in the solution is too high, it will compress the double layer of bentonite particles, inhibit the dispersion and diffusion of bentonite, and even cause the bentonite to agglomerate and coalesce.

Bentonite swelling

Bentonite swells when it encounters water. The main reason for this natural phenomenon is that the crystal layer spacing of the bentonite mineral is increased, water molecules enter the crystal layer of the mineral, and the reason for the expansion of the bentonite is the cation exchange effect of the bentonite mineral. Swellability has a great relationship with the properties of bentonite and the content of montmorillonite. The expansion of sodium bentonite is significantly stronger than that of calcareous bentonite. In addition, the expansion of bentonite with higher purity and high content of montmorillonite is stronger. Therefore, in practical application, if we mainly want to use the expansibility of bentonite minerals, we must first choose sodium bentonite ore when considering the type of bentonite mineral, and secondly consider sodium bentonite with high montmorillonite content. In mechanical casting and iron ore pellet work, the expansion requirements are high. A large amount of calcareous bentonite cannot meet the requirements for use. Therefore, the calcareous bentonite needs to be modified before use.

The degree of dispersion of sodium bentonite is higher than that of calcium bentonite, and the water absorption of sodium bentonite is high and the expansion factor is large. The reasons why sodium bentonite and calcium bentonite absorb water and swell have different results are:

1) The cations can bind the bentonite particles together, which restricts the dispersion of the bentonite particles. Polyvalent ions have a higher charge density than monovalent ions, and a stronger electrostatic attraction between the particles makes the ability of the bentonite particles to bind together. Therefore, the dispersibility of calcareous bentonite is weaker than that of sodium bentonite.

2) The negative charge generated by the montmorillonite lattice replacement must absorb the oppositely charged ions to balance the electrical properties of the solution. These oppositely charged ions exist in the form of hydrated ions, and negatively charged montmorillonite particles adsorb hydrated cations to form an electric double layer. The thickness of the electric double layer is inversely proportional to the square of the counter ion valence, that is, the cation valence is high, the hydration film is thin, and the expansion factor is low; while the cation valence is low, the hydration film is thick, and the expansion factor is high.

3) The thickness of adsorbed water by the sodium bentonite crystal layer is three layers, and the thickness of adsorbed water by the calcium bentonite crystal layer is four layers. Under the action of polar water molecules, due to the small electrostatic attraction, a large interlayer distance can be generated between the sodium bentonite crystal layers, while calcareous bentonite has a large electrical attraction between the crystal layers, and polar water molecules It is not easy to enter between the crystal layers. Therefore, the distance between the calcareous bentonite crystal layers is significantly smaller than that of sodium bentonite, which is manifested in that calcium bentonite is more difficult to disperse in water and has a lower expansion factor than sodium bentonite. In fact, the swellability of montmorillonite is controlled by its chemical composition. Montmorillonite containing many sodium ions can swell continuously until it becomes a gel state. Montmorillonite with a lot of calcium ions can only expand from the dry state to the water-containing state with a limit. After we understand the deep-seated reasons that affect the swelling properties of swelling, we can artificially and effectively control the swelling properties of bentonite minerals to achieve the best results.

Bentonite pulping properties

The pulping rate is the dispersion of bentonite particles in water to form a suspension, and the apparent viscosity of this suspension is 15 * 10-3Ps · s. The cubic number of bentonite pulping per ton is an important indicator for measuring the quality of bentonite. Generally, The pulping performance of sodium bentonite is better than calcium bentonite. The formula for calculating the pulp selection rate is:

Paddle ratio (m3 / t) = volume of water (mL) / mass of soil (g) + 1 / density of soil Generally, when the apparent viscosity is tested, the apparent viscosity is prepared at 10 ~ 25 (* 10-3 Pa · s) Three cups of mud in the range, stand still for 16 hours after stirring, and then stir, test the viscosity, then mark the three points on the single logarithmic coordinate paper, connect them, and obtain the apparent viscosity on the coordinates of 15 * Dosage at 10-3 Pa · s.

Bentonite application

The properties of montmorillonite are closely related to the type of exchangeable cations between the layers. According to the type of the main exchangeable cations between the layers, montmorillonite is usually divided into calcium montmorillonite and sodium montmorillonite.

Montmorillonite has adsorptive and cation exchange properties, which can be used to remove toxins from cooking oil, purification of gasoline and kerosene, and waste water treatment; due to its good water-swelling properties, and its dispersion and suspension and pulping properties, it is used for drilling mud, Flame retardant (suspended fire extinguishing); can also be used as a filler in the paper industry, which can optimize coating properties such as adhesion, hiding power, water resistance, scrub resistance, etc .; because of good adhesion, it can be used instead of starch Yarn sizing in the textile industry is both grain-saving and lint-free, and it does not emit a strange smell after the paddle.

In general, sodium montmorillonite (or sodium bentonite) has better properties than calcium.

Bentonite (montmorillonite) can be used as purification and decolorizing agent, binder, thixotropic agent, suspending agent, stabilizer, filler, feed, catalyst, etc. due to its good physical and chemical properties. It is widely used in agriculture, light industry and cosmetics , Medicine and other fields, so montmorillonite is a widely used natural mineral material.

Bentonite can be used as waterproof material, such as bentonite waterproof blanket, bentonite waterproof board and its supporting materials. It can be laid by mechanical fixing method. It should be used in underground environment with PH value of 4 to 10. The environment with high salt content should use modified bentonite, and it should be used after passing the test.

Bentonite composition

In 1898, American geologist Knighl discovered a greenish-yellow water-swelling clay material near the Rocky Mountain River in Wyoming, USA. Because of its origin: "Fort Beton", it was named Bentonite. Bentonite is also called bentonite or bentonite. The main mineral functional component of bentonite is montmorillonite, with a high grade content of 85-90%. Some properties of bentonite are also determined by montmorillonite.

Montmorillonite can be in various colors such as yellow-green, yellow-white, gray, white and so on. It can be compact or loose soil. It has a slippery feel when rubbed with fingers. The small block swells after adding water, and becomes suspended in water. Montmorillonite has adsorption and cation exchange properties, and can be used to remove petroleum toxins, purify gasoline and kerosene, and treat wastewater.

Development status of bentonite

Exploration research shows that China's bentonite reserves rank first in the world, with complete varieties and wide distribution, covering 26 provinces and cities, and its output and exports are among the highest in the world. According to incomplete statistics, the current annual output of bentonite in China has exceeded 3.5 million tons, and the total reserves account for 60% of the world's total. So far, it has accumulated proven reserves of more than 5.087 billion tons, and its remaining reserves are more than 7 billion tons.

More than 100 bentonite deposits have been mainly distributed in Xinjiang, Guangxi, Inner Mongolia and the three provinces of Northeast China. Among them, the reserves of bentonite deposits in Xinjiang and Buksaier Mongolia Autonomous County have exceeded 2.3 billion tons, which are currently proven reserves. The largest bentonite mining area in the country. According to the Xinjiang Geological and Mineral Department, there are 7 bentonite deposits in Hebuxel Mongolian Autonomous County, including 4 large deposits (Ulan Yingge, Riyuelei, South of Delun Mountain, and Southwest of Delun Mountain). The geological reserves of bentonite deposits in Wulanyingge mining area are 572.8 million tons, of which the on-table C-D grade bentonite ore reserves are 22.948 million tons, and off-balance-sheet D-grade reserves are 2.48 million tons, accounting for 13.74% of the nation's same-grade bentonite reserves . The geological reserves of bentonite deposits in Riyuelei mining area are 800 million tons, and the geological reserves of bentonite deposits in south and south of Delun Mountain are 210 million tons and 0.8 million tons, respectively.

Experts estimate that the prospective reserves of bentonite deposits in Wulanyinge area are expected to exceed 5 billion tons. Guangxi has Ningming, Tiandong, Chongzuo, Guiping, Hengxian and other places. The largest reserve is Ningming, which is 640 million tons, followed by Tiandong, which has 40 million tons, and the total reserves are more than 1.1 billion tons. . Inner Mongolia's Ningcheng, Xinghe, Huolin, Guyang and other places have very rich bentonite deposits, and the largest reserve is Chifeng Ningcheng, which exceeds 1 billion tons. The rest are distributed in Jiangsu, Sichuan (Nanchong) Hebei, Hubei, Shandong, Anhui, Zhejiang, Jiangxi, Henan, Shaanxi and Gansu. It can be seen that the high concentration of bentonite ore resources is conducive to the establishment of large-scale enterprise groups, the establishment of large-scale production bases, and the development of specialization, large-scale, and intensive development.

According to forecasts, the amount of bentonite ore resources in China has exceeded 8 billion tons, laying a resource foundation for the development and research of new products, market development, and improvement of competitiveness. However, the degree of development and utilization of bentonite in China is very low, and the cumulative mining volume is less than 1% of the proven reserves. In the international market, it is a situation of "low out and high advance", that is, exporting low-level products (raw ore, foundry, drilling, low-grade activated clay, etc.), and importing high-level products (detergent for fabric detergent, high-grade organic soil, etc.).

According to incomplete statistics, China's annual output and sales of bentonite products are about 6 million tons. The industry is characterized by the small scale of the company (a handful of companies with an annual output of more than 10,000 tons), the low level of technology, the competition is not fierce due to the resource-based industry, and the production, sales and prices have increased year by year.

Preparation and application of bentonite

Method and process

1.Semi-wet method for producing highly effective activated clay

2. Catalytic acid treatment of sepiolite and bentonite

3. Preparation method of antifouling bentonite 4. New method of comprehensive utilization of waste white clay residue

4. Compound Chinese herbal medicine bentonite feed additive

5.Methods for improving pollution resistance of montmorillonite clay

6. Modified bentonite and its application 8. Modified bentonite composition

7. Dry production method of organic bentonite

8. Waste white clay treatment method containing denitrifying agent and waste oil

9. Recycling process of granular white clay for aviation coal decolorization

10.Synthetic octahedra montmorillonite clay

11. Preparation method of activated clay

12.Production method of activated clay

13.Activated white clay production method 2

14. Method for producing activated clay 3

15. Process for producing P-type washing zeolite by alkaline activated bentonite

16. Grafted bentonite super absorbent material and its manufacturing method

17. Manufacturing method of lithium bentonite suspension agent

18.Production method of lithium bentonite

(Two) equipment selection

1. Classified impact mill, this equipment has the advantages of adjustable particle size and large output;

2. Ring mill. This equipment is suitable for intensive production lines. The adjustable particle size of crushed bentonite is wide and the output is large.

Introduction to Bentonite Technology

Bentonite foreign technology

The United States has been a leader in the study of bentonite in the world, and many of the standards for domestic bentonite products are based on American standards. Some European countries, Japan, and South Korea also have more advanced technologies on some products. Compared with foreign countries, domestic products and market development are relatively slow, and products are mainly conventional products. This has a lot to do with the domestic environment, policies and the status of resources.

Bentonite domestic technology

In the early days, the research and development of domestic bentonite was mainly concentrated in Zhejiang, and relatively high-end domestic products were also concentrated in this production. The enterprises are represented by Zhejiang Huate and Zhejiang Fenghong. In recent years, many domestic universities and research institutes have made great progress in the research of bentonite, and have a series of bentonite deep processing technologies. More representative are Wuhan University of Technology, China University of Mining and Technology, China University of Geosciences, Suzhou Non-Mining Institute, and Zhengzhou Institute.

China Non-metallic Minerals Corporation's strategic minerals are bentonite. There are bentonite companies in Xinjiang, Hubei, and Beijing. The products cover metallurgy, steel, drilling, building waterproofing and other fields. Its technology center develops new products based on its own companies. It has a large number of scientific research results and independent intellectual property rights in environmental protection, new waterproofing, purification and other technologies. With its unique advantages and technical expertise, it has formed a new research and development base in North China.

How to identify bentonite

In the visual inspection, the high-quality bentonite is pure white, usually gray or light yellow-white, and it is often light green, light green, rose red and other colors due to water absorption or containing impurities. After air-drying, it is still pure white, gray or light yellow-white. The section was uneven after being opened by hand, but was jelly-like. Oily luster, slippery touch. Can absorb water and swell, and can become colloid. After long-term air-dried water is lost, it can become loose again. Bentonite can absorb or absorb various colors due to its strong ion exchange force. Mix it with grease to make it smoother. Its fine powder and water suspension have good dispersion (divergence) and are not easy to settle. Types of natural bentonite are mainly divided into calcium, sodium, hydrogen, hectorite and so on based on the relative content of cations of montmorillonite. Among them, the clay based on montmorillonite is called calcium-based bentonite. Most of the bentonite mines in China mainly produce calcium-based bentonite. Calcium-based bentonite is cheaper and easier to obtain than sodium-based bentonite, so we use calcium-based soil in broiler and laying hen experiments. Feed the chicken with bentonite additives, because the palatability is good, and the chicken loves to eat.
However, it is not accurate enough to rely on the naked eye and other sensory evaluations. There is no uniform national standard for the identification of bentonite in China. Most mines implement the Ministry of Machinery's "Ministry Standards for Foundry Bentonite and Clay" (1997) and enterprise standards. The main measures are blue absorption, moisture, colloidal media, pass rate, wet pressure strength, expansion coefficient, pH, etc. The measurement methods and standards are omitted here.

Bentonite Industry Index

The general industrial requirement for the quality of bentonite ore is measured by the content of montmorillonite in the ore:

Boundary grade: 40%;

Industrial average grade: 50% o

The content of montmorillonite is generally converted by the amount of blue absorption.

M = B / K'100

Relative content of montmorillonite in M-bentonite ore,%:

BBlue absorption, mg equivalent / 100 g sample:

Kconversion factor, 150.

Available thickness: 1-2m;

Stone removal thickness: 1m. ^[3]