The modification operation of bentonite usually uses three methods, such as physical, chemical and mechanical, to treat the surface of natural bentonite. According to the desired purpose, the physical or chemical properties of the bentonite surface are changed to meet the needs of different technical fields. For the application of bentonite, it can also improve the function and use value of the bentonite itself, some are used to change the characteristics of the bentonite, some change a certain ability of the bentonite, and improve the corresponding ability effect.
What are the most common bentonite modification methods? After finishing, Xiaobian found that there are five modification methods: acid modification, roasting and calcination method, sodium modification method, salt modification method, organic modification method, etc. Let's learn more about it below.
1. Sodium modification method
In the practical application of bentonite, it is found that the exchange capacity of Ca2+ in calcium-based soil is much lower than that of Na+. Therefore, calcium-based soil is often put into the market after sodiumization. Commonly used sodiumizing agents are NaF, Na2CO3, NaCl, NaNO3, NaSO, etc.
2. Firing activation modification method
The calcination activation modification method is to calcine bentonite at different temperatures for a certain period of time. This calcination causes the bentonite to lose the water on the surface, the bound water in the skeleton structure, and the organic pollutants in the pores in turn, resulting in an increase in the air rate and a looser structure, which ultimately increases the adsorption of the bentonite.
3. Organic modification method
The principle of the organic modification method is to organicize the bentonite to obtain an organic composite bentonite. This modification method completely changes the bentonite from hydrophilic and oleophobic, which is called lipophilic and hydrophobic. The purpose of organic modification is to increase the interlayer distance of bentonite to enhance the ability of bentonite to remove organic matter.
4. Inorganic modification method
The principle of the inorganic modification method is similar to the organic modification method, mainly through the expansion characteristics of bentonite and the exchangeability of cations between layers of bentonite, these two characteristics, the modification of natural bentonite. After the natural bentonite is inorganically modified, the spacing between the layers is significantly increased, which can also improve the adsorption effect.
5. Inorganic/organic composite modification method
The principle of inorganic/organic composite modification method is based on two characteristics of bentonite: 1. The interlayer gap of bentonite is relatively large; 2. The cation exchangeability of bentonite. The method is to use inorganic polymers to stretch the interlayer domains of bentonite to make the distance larger, and then change the surface properties of bentonite through activators.
The commonly used preparation method is to first treat bentonite with polyhydroxy cations, so that the interlayer domain of bentonite increases, resulting in charge reversal, and then adding organic surfactants to change its surface properties.