Bentonite

Bentonite, also known as porphyry, is a non-metallic mineral mainly composed of montmorillonite, and is also a widely used natural mineral material.

It be used as a purification and decolorization agent, binder, thixotropic agent, suspension agent, catalyst due to the excellent physical and chemical properties. It is widely used in agriculture, light industry, cosmetics, pharmaceuticals, and other fields.

Bentonite contains over 10 types of mineral elements, most of are essential constants and trace elements for the growth and development of poultry and domestic animals. Adding bentonite to feed makes animals energetic, with smooth feathers, high survival rates, and strong disease resistance. Suspension agents have good bioavailability and are easier to produce and use, especially for children and elderly people with swallowing difficulties, bringing convenience to medication. Bentonite is a high-performance suspension agent that can assist in suspension.

The main component of bentonite, montmorillonite, has a layered structure and uneven electrical distribution, which has a strong selective adsorption effect on some viruses, pathogens, and toxins in the digestive tract. SMECTA is a digestive tract adhesive protector developed by French company Epson, mainly composed of montmorillonite.

In the cosmetics industry, the skin care facial mask often contains bentonite. Bentonite is not only used as a filler to reduce costs, but also has good effects on skincare. For example, using bentonite has a certain oil absorption and cleaning effect. A certain amount of bentonite can be added to our common blackhead removal facial mask products.

Bentonite is a type of clay rock, also known as montmorillonite clay rock. It often contains small amounts of illite, kaolinite, halloysite, chlorite, zeolite, quartz, feldspar, calcite, etc; Generally white or light yellow. Due to changes in iron content, it appears as light gray, light green, pink, brownish red, brick red, gray black, etc; Having a waxy, earthy, or oily luster; Some bentonite is loose like soil, while others are dense and hard. The main chemical components are silica, alumina, and water, as well as elements such as iron, magnesium, calcium, sodium, and potassium. The content of Na2O and CaO has a significant impact on the physicochemical properties and technological performance of bentonite. Montmorillonite minerals belong to the monoclinic crystal system, usually in the form of earth like blocks, 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 types, contents, and interlayer charges of exchangeable cations in montmorillonite, bentonite can be divided into sodium bentonite (alkaline soil), calcium bentonite (alkaline soil), and natural white clay (acidic soil or acidic clay). Calcium bentonite based bentonite includes calcium sodium based bentonite and calcium magnesium based bentonite.

Bentonite has strong hygroscopicity and swelling properties. It can absorb 8 to 15 times its own volume of water, and its volume can expand several times to 30 times. It can be dispersed into gel and suspension forms in water medium. The medium solution has certain viscosity, thixotropy, and lubricity; Has strong cation exchange ability; Has a certain adsorption capacity for various gases, liquids, and organic matter, with a maximum adsorption capacity of up to 5 times its own weight; Compatible with mixtures of water, mud, or fine sand, possessing plasticity and adhesion; Surface active acidic clay (active clay, natural clay acidic clay) can absorb colored ions.

Cat litter has always been the largest application market for bentonite, accounting for 29% of its total consumption. When encountering cat feces and urine, bentonite cat litter will quickly clump together. Bentonite, as cat litter, requires strong ability to adsorb liquids and odors, uniform particle size, and does not disintegrate when exposed to moisture.

Bentonite can be in the form of dense blocks or loose soil. It feels very slippery when rubbing with your fingers. After adding water, the volume of small pieces expands several times to 20-30 times. It is suspended in water and turns into a paste when there is little water. Shape. The properties of montmorillonite are related to its chemical composition and internal structure.

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

Physical adsorption. Physical adsorption is generated by the intermolecular attraction between the adsorbent and the adsorbate, commonly known as van der Waals forces. Physical adsorption is a reversible adsorption process, and the adsorption rate and desorption rate exhibit dynamic equilibrium under certain conditions. The main reason for physical adsorption is that the molecules on the surface of bentonite have surface energy. Due to the high dispersion of bentonite in water, the physical adsorption phenomenon is very obvious.

Chemical adsorption. Chemical adsorption is generated by the chemical bonding force between the adsorbent and the adsorbate, and the chemical adsorption effect is generally irreversible. Chemical adsorption is significantly more stable than physical adsorption. Therefore, the bentonite mud treated with iron chromium lignosulfonate has high temperature resistance and can be used as a high-temperature mud system for geothermal and ultra deep wells.

Ion exchange adsorption. Bentonite mineral crystals generally carry negative charges, so they need to adsorb equivalent amounts of opposite charged cations on the surface of bentonite particles. The reaction of ion exchange adsorption is reversible, and the speed of adsorption and desorption is influenced by ion concentration, which conforms to the law of mass action.

Expansibility: Bentonite expands when exposed to water. The main reason for this natural phenomenon is that the distance between the crystal layers of bentonite minerals increases, and water molecules enter the crystal layer of the mineral. In addition, the reason for the expansion of bentonite is the cation exchange effect of bentonite minerals. The expansion properties are closely related to the properties of bentonite and the content of montmorillonite. The swelling property of sodium bentonite is significantly stronger than that of calcium bentonite. In addition, bentonite with higher purity and higher content of montmorillonite has stronger swelling performance.

Slurry making ability: The slurry making 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 number of cubic meters of slurry made per ton of bentonite is an important indicator to measure the quality of bentonite. Generally, the slurry making performance of sodium bentonite is better than that of calcium bentonite. The formula for calculating the slurry selection rate is:

Paddle making rate (m3/t)=volume of water (mL)/mass of soil (g)+1/density of soil. Generally, when testing the apparent viscosity, three cups of mud with an apparent viscosity range of 10-25 (* 10-3 Pa • s) are prepared. After stirring and standing still for 16 hours, the mud is stirred and tested for viscosity. Then, the positions of the three points are marked on a single logarithmic coordinate paper and connected. The amount of soil added at an apparent viscosity of 15 * 10-3 Pa • s is calculated on the coordinate.

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

Bentonite can be used as waterproof materials, such as bentonite waterproof blankets, bentonite waterproof boards and their supporting materials, which are laid using mechanical fixation method. Applied to underground environments with pH values ranging from 4 to 10, modified bentonite should be used in environments with high salt content, and should be tested and qualified before use.