Introduction

Bentonite is a non-metallic mineral with montmorillonite as its main mineral component. The structure of montmorillonite is a 2:1 crystal structure composed of two silicon-oxygen tetrahedrons sandwiching a layer of aluminum-oxygen octahedron. Due to the layered structure formed by the montmorillonite unit cell contains certain cations, such as Cu, Mg, Na, K, etc., and the interaction between these cations and the montmorillonite unit cell is very unstable and is easily exchanged by other cations, so it has good ion exchange properties. Abroad, it has been used in more than 100 departments in 24 fields of industrial and agricultural production, with more than 300 products, so it is called "universal soil".

Our country has a long history of developing and using bentonite, which was originally used as a detergent. (There were open-pit mines in the Renshou area of Sichuan hundreds of years ago, and the locals call bentonite soil powder). It is actually widely used but only has a history of a hundred years. The first discovery in the United States was in the ancient strata of Wyoming. Yellow-green clay can swell into a paste after adding water. Later, people referred to all clays with this property as bentonite. In fact, the main mineral component of bentonite is montmorillonite, with a 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, etc. It can be in the form of dense blocks or loose soil. It feels slippery when rubbed with fingers. The volume of small blocks expands several times to 20-30 times after adding water. It is suspended in water and becomes mushy when there is less water. The properties of montmorillonite are related to its chemical composition and internal structure.

Sodium bentonite is classified according to the type and content of exchangeable cations between montmorillonite layers: sodium bentonite has a basicity coefficient greater than or equal to 1, and calcium bentonite has a basicity coefficient less than 1.

Due to different sodiumification conditions, artificial sodium bentonite has different failure temperatures, but they are all lower than natural sodium bentonite. The swelling force of natural sodium bentonite is greater than that of artificial sodium bentonite, natural sodium bentonite has higher c-axis order than artificial sodium bentonite, has finer grains and stronger dispersion. Sodium bentonite has superior physical and chemical properties and process technology performance than calcium bentonite. The main manifestations are: slow water absorption, but large water absorption and expansion ratio; high cation exchange capacity; good dispersion in water medium, high colloid; its colloidal suspension has good thixotropy, viscosity, lubricity, and high pH value; good thermal stability; high plasticity and strong adhesion; high hot wet tensile strength and dry compressive strength. Therefore, sodium bentonite has higher use value and economic value. The physical and chemical properties of artificial sodium bentonite depend not only on the type and content of montmorillonite it contains, but also on the method of artificial sodium and the degree of artificial sodium.

Application:

It is used as binder, adsorbent, catalyst, thickener, thixotropic agent and decolorizing agent in metallurgy, casting, drilling, chemical industry, food and other fields. In agriculture, it can be used as a soil conditioner, feed additive and pesticide carrier; in the food industry, it is used as a purifier for juice and wine, as well as a concrete plasticizer and a paint tackifier. Organic bentonite is used as a thickener for lubricating grease, an anti-settling agent for paints, inks and coatings, high-temperature deep well oil cement slurries,  a thickener and stabilizer for latex paints and cosmetics, etc.