the basic nature of bentonite
Bentonite, also known as bentonite, bandengyan, is a claystone with montmorillonite as the main mineral. Pure bentonite is rare and contains unequal amounts of impurities such as quartz, feldspar, mica and zeolite. , Its purity varies by origin. The composition of the montmorillonite is (Na, Ca) 0. 33 (Al, Mg) 2 Si4 O10 (OH) 2 · H2 O, the theoretical chemical composition of SiO2 66. 72%, Al2 O3 28.53%, H2 O5 %. Common montmorillonite has two kinds of sodium and calcium.
Montmorillonite is an aqueous layered aluminosilicate mineral consisting of two aluminum (magnesium) oxyhydroxide octahedra between the two silicon tetrahedra and belongs to the 2: 1 type three-layered clay mineral. 96 ~ ~ 2. 14nm; water molecules or other exchangeable cations Can enter the floor. In addition, in the clay mineral formation, isomorphous substitution often occurs; in the tetrahedral of montmorillonite, not more than 1/15 of Si4 + is replaced by Al3 +, and 1/3 to 1/6 of Al3 + Is replaced by Mg2 +, causing a permanent negative charge between the crystal layers; this negative charge is balanced by K +, Na +, etc. outside the layered structure. Bentonite has a large surface area (600 ~ 800m2 / g), it not only has a large outer surface, but also has a huge inner surface; huge surface area with a huge surface energy, so that it has a larger adsorption capacity. These characteristics determine the montmorillonite has a high cation exchange capacity (80 ~ 120meq / 100g) and good adsorption properties; lay the foundation for the application of bentonite and modified bentonite in water treatment.