Bentonite & Talc Powder
Bentonite is a nonmetallic mineral with montmorillonite as its main mineral component. Montmorillonite structure is a 2:1 crystal structure composed of two silico-oxygen tetrahedrons sandwiched by a layer of alumino-oxygen octahedrons. Some cations exist in the layered structure formed by montmorillonite cells, such as Cu, Mg, Na, K, etc., and the interaction between these cations and montmorillonite cells is very unstable. It is easy to be exchanged by other cations, so it has good ion exchange property. Foreign countries have been used in 24 fields of industrial and agricultural production in more than 100 departments, there are more than 300 products, so people called “universal soil”.
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Description
Brief Introduction
Bentonite is a kind of clay rock, also known as montmorillonite clay rock, often bentonite contains a small amount of illite, kaolinite, alloxite, chlorite, zeolite, quartz, feldspar, calcite, etc. Generally white, light yellow, because of iron content changes and light gray, light green, pink, brown red, brick red, gray black, etc.; Having a waxy, earthy or greasy sheen; Some bentonites are loose like soil, while others are dense and hard. The main chemical components of bentonite are silicon dioxide, aluminum oxide and water, but also contain iron, magnesium, calcium, sodium, potassium and other elements. The content of Na2O and CaO has a great influence on the physical and chemical properties of bentonite and the technological performance. Montmorillonite minerals belong to the monoclinic crystalline system, which is usually an earth-like block, white, sometimes with light red, light green, light yellow and other colors. The luster is dull. Hardness 1~2, density 2~3g/cm3. According to the type, content and interlayer charge of exchangeable cations of montmorillonite, bentonite can be divided into sodium bentonite (alkaline soil), calcium bentonite (alkaline soil), natural bleached soil (acid soil or acid white soil), among which calcium bentonite also includes calcium sodium base and calcium magnesium base. Bentonite has strong moisture absorption and expansion, can absorb 8~15 times of its own volume of water, volume expansion can reach several times to 30 times; In the water medium can disperse into gelling and suspension, the medium solution has a certain viscosity, thixotropy and lubricity; Strong cation exchange ability; It has certain adsorption capacity for various gases, liquids and organic substances, with the maximum adsorption capacity up to 5 times its own weight; Its admixture with water, mud or fine sand has plasticity and bonding property. Acid bleached soils with surface activity (active bleached soils, natural bleached soils – acid bleached soils) can absorb nonferrous ions.
Adsorbability
Adsorption is a natural phenomenon in the existence of all solid substances. The phenomenon that we gather certain molecules on the surface of bentonite is called adsorption of bentonite. This adsorption is widely used in industry. For example, drilling mud often uses the adsorption characteristics of bentonite minerals to adjust mud parameters for different purposes, such as adding fluid loss agent, is through the polymer adsorption on the surface of bentonite particles at one end, the other end dissolved in water so that bentonite particles and water molecules produced an indirect relationship. A bridging action is formed, which reduces the free water in the mud, changes the mud performance parameters, and achieves the purpose of reducing the filtration rate.
Bentonite adsorption can be divided into physical adsorption, chemical adsorption and ion exchange adsorption.
| l) Physical adsorption. Physical adsorption is produced by the intermolecular attraction between adsorbent and adsorbent, that is, we often say van der Waals force. Physical adsorption is a reversible adsorption process. The adsorption velocity and desorption velocity are in dynamic equilibrium under certain conditions. The main reason of physical adsorption is the surface energy of bentonite surface molecules. Because bentonite is highly dispersed in water, the physical adsorption phenomenon is very obvious. | |||
| 2) Chemisorption. Chemisorption is produced by the chemical bond force between adsorbent and adsorbent. Chemisorption is generally irreversible. The application of chemical treatment agents in drilling mud is a typical example of chemisorption. For example, when iron chromium lignosulfonate is added to bentonite mud, chromium ions are integrated and adsorbed on the edges of bentonite crystals. This chemisorption is significantly more stable than physical adsorption. Therefore, the bentonite mud treated with Fe-Cr lignosulfonate has high temperature resistance and can be used as a high-temperature resistance mud system for geothermal and ultra-deep Wells. | |||
| 3) Ion exchange adsorption. Bentonite mineral crystals are generally negatively charged, so cations with equal equivalent charge should be adsorbed on the surface of bentonite particles. The adsorbed cations can exchange with the cations in solution, which is called ion exchange adsorption. The characteristics of ion exchange adsorption are: the same number of ions exchange with each other, equal energy exchange with each other. The reaction of ion exchange adsorption is reversible, and the rate of adsorption and desorption is affected by ion concentration, which conforms to the law of mass action. |
The factors affecting the adsorption of bentonite minerals are:
| 1) The influence of bentonite type. The adsorption capacity of sodium bentonite is obviously stronger than that of calcium and other bentonite minerals. | |||
| 2) The effect of pulverized bentonite particle size. According to the theory of solid adsorption, the adsorption capacity of crushed bentonite mineral is obviously improved, and the finer the crushed mineral is, the stronger the adsorption is. | |||
| 3) The influence of solution medium. According to the double layer theory, bentonite mineral crystals are negatively charged, and ion exchange occurs when the double layer is formed. If the concentration of ions in the solution is too high, it will compress the double electric layer of bentonite particles, inhibit the dispersion and diffusion of bentonite, and even make the bentonite coagulate and coalesce. |
Expansibility
| Bentonite expands when it meets water. The main reason for this natural phenomenon is that the spacing between crystal layers of bentonite minerals increases, and water molecules enter the crystal layers of minerals. In addition, the cation exchange of bentonite minerals also causes the expansion of bentonite. The swelling property of sodium bentonite is obviously better than that of calcium bentonite. In addition, the swelling property of bentonite with higher purity and montmorillonite content is better. Therefore, in practical application, if we mainly want to use the expandability of bentonite minerals, then we should first choose sodium bentonite ore when considering the types of bentonite minerals, and then consider sodium bentonite with high content of montmorillonite. In mechanical casting and iron ore pelletizing work, the expansibility requirement is higher. A large amount of calcium bentonite can not meet the requirements of use, so it is necessary to modify the calcium bentonite before use. | |||
| The dispersion degree of sodium bentonite is higher than that of calcium bentonite, sodium bentonite has higher water absorption and larger expansion ratio. The reasons for the different results of water absorption and swelling of sodium bentonite and calcium are as follows: | |||
| 1) Cations can bind bentonite particles together, restricting the dispersion of bentonite particles. The charge density of polyvalent ions is higher than that of univalent ions, and the electrostatic attraction between particles is stronger, which makes the bonding ability of bentonite particles stronger. Therefore, the dispersion ability of calcium bentonite is weaker than that of sodium bentonite. | |||
| 2) The negative charge generated by the lattice replacement of montmorillonite needs to absorb ions with opposite electrical properties to balance the electrical properties of the solution. These electrically opposite ions exist in the form of hydrating ions in the solution, and the negatively charged montmorillonite particles adsorb the hydrating cations to form a double electric layer. The thickness of the double electric layer is inversely proportional to the two squares of the valence number of the counter ions, that is, the cation price is high, the hydration film is thin, and the expansion ratio is low. The cation valence efficiency is low, the hydration film is thick, the expansion ratio is high. | |||
| 3) The thickness of sodium bentonite crystal layer adsorbed water is three layers, and the thickness of calcium bentonite crystal layer adsorbed water is four layers. Under the action of polar water molecules, sodium bentonite crystal layers can produce large interlayer spacing due to the low electrostatic attraction, while calcium bentonite due to the high electrostatic attraction between crystal layers, polar water molecules are not easy to enter the interlayer. Therefore, the distance between crystal layers of calcium bentonite is obviously smaller than that of sodium bentonite. Calcium bentonite is more difficult to disperse in water than sodium bentonite, and its expansion ratio is lower. Essentially, the dilatability of montmorillonite is controlled by its chemical composition. The sodium-rich montmorillonite can be continuously expanded until it becomes a gel state. Calcium – rich montmorillonite can only expand from dry operation state to water state is limited. By understanding the underlying reasons that affect the swelling property of bentonite, we can control the swelling property of bentonite minerals artificially and effectively, so as to achieve the best use effect. |
Pulping Property
| Pulping rate refers to the dispersion of bentonite particles in water to form a suspension, and the cubic number of bentonite slurry per ton when the apparent viscosity of this suspension is 15*10-3Ps·s is an important index to measure the quality of bentonite. Generally, the slurry performance of sodium bentonite is better than that of calcium bentonite. The formula for calculating the pulp separation rate is: | |||
| Pulping rate (m3/t)= volume of water (mL)/ mass of soil (g)+1/ density of soil is generally prepared during the test of apparent viscosity. The apparent viscosity is three cups of mud within the range of 10~25(*10-3 Pa·s). After stirring, the mud is placed at rest for 16h, and then stirred to test the viscosity. The amount of soil added when the apparent viscosity is 15*10-3 Pa·s is calculated on the coordinates. |
Industrial Index
| General industrial requirements for the quality of bentonite ore are measured in terms of montmorillonite content in the ore: | |||
| Boundary grade :≥40%; | |||
| Industrial average grade :≥50% | |||
| The content of montmorillonite is generally converted by the amount of blue absorption. That is: | |||
| M=B/K’100 | |||
| Relative content of montmorillonite in M- Bentonite ore, %: | |||
| B- Blue absorption, mg equivalent / 100g sample: | |||
| K- conversion factor, 150. | |||
| Recoverable thickness :1-2m; | |||
| Stone removal thickness :≥1m. |
Talc powder, called PULVISTALCI in English, is white or almost white, fine, non-sandy powder, greasy touch. Odorless, tasteless. This product is insoluble in water, dilute mineral acid or dilute alkali hydroxide solution. It can be used medicinally.
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Main component
The main component of talc is magnesium silicate containing talc water. The molecular formula is Mg3[Si4O10](OH)2. Talc belongs to monoclinic crystal system. Crystals in pseudohexagonal or rhomboidal sheets, rarely seen. Usually a dense mass, blade – shaped, radial, fibrous aggregate. Colorless transparent or white, but because of a small amount of impurities and appear light green, light yellow, light brown and even light red; The cleavage surface is pearly. Hardness 1, specific gravity 2.7~2.8.
Basic characteristic
| Talc has excellent physical and chemical properties such as lubricity, viscosity resistance, flow aid, fire resistance, acid resistance, insulation, high melting point, chemical inactivity, good covering power, softness, good luster, strong adsorption force, etc., because the crystalline structure of talc is layered, it has the tendency to easily split into flake and special smoothness. If the content of Fe2O3 is very high, it will reduce its insulation. | |||
| Talc is soft, its hardness coefficient is 1~1.5, slippery, {001} cleavage is complete, easy to split into flakes, natural Angle of rerest is small (35°~40°), extremely unstable, surrounding rock is silicified and slippery magnesite, magnesite, lean ore or dolomitic marble, except a few moderately stable, generally unstable, joint, crack development, The physical and mechanical properties of ore and surrounding rock have great influence on mining technology. |
Physical Property
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Chemical Grade
Application: Used as reinforcement filler in rubber, plastic, paint and other chemical industry. Features: Increase the stability of the product shape, increase the tensile strength, shear strength, bending strength, pressure strength, reduce deformation, elongation rate, coefficient of thermal expansion, high whiteness, particle size uniform dispersion and so on.
Ceramic grade
Application: Used for manufacturing high frequency porcelain, wireless electric porcelain, various industrial ceramics, building ceramics, daily ceramics and ceramic glaze. Features: High temperature does not change color, after forging and burning whiteness enhancement, uniform density, good luster, smooth surface.
Cosmetic grade
Use: It is a premium filler for the cosmetic industry. Features: Contains a lot of silicon element. It has the function of blocking infrared rays, thus enhancing the sunscreen and anti-infrared properties of cosmetics.
Pharmaceutical food grade
Application: Used as additive in medicine and food industry. Features: Non-toxic, tasteless, high whiteness, good tolerability, strong gloss, soft taste, strong smoothness. The PH value is 7-9 and will not degrade the properties of the original product.
Paper grade
Purpose: Used for various high and low grade paper industry products. Characteristics: Papermaking powder has the characteristics of high whiteness, stable particle size and low abrasion. The paper made of this powder can achieve smooth and delicate paper, save raw materials, and improve the service life of the fat net.
Magnesite powder
Application: Used for manufacturing electric porcelain, wireless electric porcelain, various industrial ceramics, building ceramics, daily ceramics and ceramic glaze, etc. Features: High temperature does not change color, after forging and burning whiteness enhancement, uniform density, good gloss, smooth surface.
Additional information
| Weight | 24 kg |
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| Dimensions | 12 × 48 × 62 cm |
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