What exactly is the difference between montmorillonite and zeolite?(1)

Zeolite is a water-bearing alkali metal or alkaline earth metal silica-aluminate mineral, which is a tetrahedron composed of three elements: silicon (Si), aluminum (Al), and oxygen (O), among which the silicon and oxygen tetrahedra and the aluminum-oxygen tetrahedra form an infinitely expanding three-dimensional space-like structure. In the tetrahedral structure of zeolite, the negative charge caused by replacing silicon ions with aluminum ions is balanced by sodium, potassium, calcium and magnesium ions, etc. Therefore, zeolite has strong ion exchange properties.

In addition, zeolite itself has a regular porous structure, and its pores are comparable to the molecular size of general substances, with a diameter of about 0.3~1nm, and its specific surface area is as high as 400~800m2/g. The special physical structure makes zeolite have strong selective adsorption characteristics, and nowadays zeolite has been widely used in many fields such as water treatment, soil remediation, green building materials, petroleum processing, and daily chemical industry.

Montmorillonite is a clay mineral with large specific surface area and wide distribution, also known as microcrystalline kaolinite, which is one of the main active components in soil (zeolite generally contains a small amount of zeolite as well). Montmorillonite has a 2:1 type of layered structure, the unit cell is a structural layer formed by two Si-O tetrahedra with the top angle facing inward, sandwiched between a piece of Al-O or Mg-O octahedra, there is no shared oxygen or hydroxyl between the layers, so the bond between the layers is very weak. Generally, most of them are yellow-green, yellow-white, gray, white, etc., and can be dense lumps or loose clay.

Due to the fine particles of montmorillonite (generally <2 μm), large specific surface area and special structural domains, etc., it has swelling properties in addition to adsorption and ion exchange properties.

In addition, the modified montmorillonite has a wide range of applications in livestock (pigs, rabbits) breeding, especially for piglets, suckling pigs, young rabbits and other dysentery to play a good prevention, management effect, and can also be used as feed demolders, feed auxiliary additives materials. However, because of the large number of inorganic ions distributed between the layers of montmorillonite, the surface is hydrophilic and oleophobic, which is not conducive to dispersion in polymers, so when using this material, it must be modified organically, and is not recommended for direct use.

The pore size distribution of zeolite is uniform and mostly below 10nm, which is comparable to the molecular size of general substances, and thus has the selective adsorption property of molecular sieve. Moreover, in the structure of zeolite, the negative charge on the anion lattice and the center of the positive charge of the balanced cation do not overlap in space, so that zeolite has a large electrostatic attraction inside. It is this electrostatic force that makes zeolites preferentially selective for the adsorption of polar, unsaturated and easily polarized molecules. In addition, zeolite also - has a selective effect on the polar size of molecules, the greater the polarity can be the more easily polarized substances, the easier it is to be adsorbed.