Bentonite adsorption can be divided into physical adsorption, chemical adsorption and ion exchange adsorption three types.
l) Physical adsorption. Physical adsorption is adsorbed by the adsorbent between the molecules produced between, that is, we often say Van der Waals forces. Physical adsorption is a reversible adsorption process. The adsorption rate and desorption rate are dynamically balanced under certain conditions. The main reason for the physical adsorption is that the bentonite surface molecules have their surface energy. Due to the highly dispersed bentonite in water, physical adsorption phenomenon is very obvious.
2) chemisorption. Chemical adsorption is based on the chemical bond between the adsorbent and the adsorbate generated, and chemical adsorption is generally irreversible. Application of chemical treatments to drilling muds is a classic example of chemisorption. For example, the addition of iron chromium lignosulphonate to bentonite mud is the use of chromium ions to integrate and adsorb onto the edges of bentonite crystals. This chemisorption significantly than physical adsorption to be stable. Therefore, bentonite mud treated with iron chrome lignosulphonate has high temperature resistance and can be used as a high temperature resistant mud system for geothermal and ultra-deep wells.
3) Ion exchange adsorption. Bentonite mineral crystals generally have a negative charge, so the bentonite particles adsorb an equivalent amount of oppositely charged cations. Adsorbed cation and the solution of the cation exchange, this effect is called ion exchange adsorption. Ion exchange adsorption is characterized by: the same number of ions exchange, and other power exchange. Ion exchange adsorption reaction is reversible, adsorption and desorption rate by the ion concentration, this effect in line with the law of mass effect.