Montmorillonite

Bentonite, known as the "universal clay", is a natural clay mineral containing Montmorillonite as its main component. Its magic stems from its unique physical and chemical properties. From the appearance, bentonite is mostly white, gray white or light yellow in color, with delicate texture, oily or waxy luster, opaque, and low hardness (2.0-2.5), but its internal properties are extremely rich.

The most significant characteristic is water absorption and swelling. When bentonite encounters water, the cations (such as sodium and calcium) in its layered structure combine with water molecules, causing the interlayer spacing to rapidly expand and the volume to expand several times or even more than ten times. This expansion ability makes it highly effective in fields such as sealing and anti-seepage. For example, in underground engineering, the bentonite forms gel like material after encountering water, which can effectively fill the gap and prevent water seepage.

Secondly, bentonite has strong adsorption and cation exchange capabilities. Montmorillonite has negative interlayer charges and can adsorb cations in solution, such as calcium, magnesium, ammonium, etc., and achieve reversible exchange. This characteristic makes it widely used in wastewater treatment, soil improvement, and feed additives. In the field of environmental protection, it can adsorb heavy metal ions and organic pollutants; In agriculture, it can be used as a carrier for slow-release fertilizers to improve nutrient utilization efficiency.

In addition, bentonite also has good adhesion, plasticity, thixotropy, and suspension properties. In the casting industry, as a sand binder, it can maintain the strength and breathability of the sand mold; In drilling mud, it can suspend rock debris, stabilize the wellbore, and prevent hole collapse. Its thixotropy shows that it is in the form of gel at rest and turns into sol after stirring, which makes it used as a thickener and stabilizer in coatings and greases.

According to the different interlayer cations, bentonite can be divided into sodium based, calcium based, magnesium based, and calcium sodium based types. Among them, sodium based bentonite has better performance, high expansion ratio, and good colloidal stability, and is commonly used in high demand scenarios. Calcium based bentonite can improve its performance and expand its application range through "sodium modification".

It is worth mentioning that bentonite also has certain catalytic activity and thermal stability, and can be used as a catalyst carrier in the petrochemical industry. Its melting point is as high as 1330-1430 ℃, making it suitable for use in high-temperature environments.