What are the differences between sodium-based bentonite and calcium-based bentonite?

The differences between sodium-based Bentonite and calcium-based bentonite are as follows:
Chemical composition
- Cation species: Sodium Bentonite interlayer cations are mainly sodium ions (Na⁺), while calcium bentonite interlayer cations are mainly calcium ions (Ca²⁺).
- Cation exchange capacity: sodium-based bentonite has a high cation exchange capacity, generally 800-1000 mL/kg, calcium-based bentonite has a relatively low cation exchange capacity of about 600-650 mL/kg.
Physical Properties
- Viscosity: sodium bentonite viscosity is higher than calcium bentonite, under the same conditions, sodium bentonite gum price is higher, can reach 100%, while calcium bentonite gum price is about 60%.
- Water Absorption: sodium bentonite water absorption is larger, up to 500% or more, slower water absorption; calcium bentonite water absorption is smaller, up to no more than 200%, fast water absorption.
- Expansion: sodium-based bentonite expansion times higher, up to 20-30 times; calcium-based bentonite expansion times lower, generally 8-10 times.
- PH value: sodium bentonite pH value is alkaline, generally between 8.5-12.6; calcium bentonite pH value is neutral, the test value of 6-7.5.
- Dispersibility: sodium bentonite in the water dispersion is better, put into the water is not easy to produce precipitation; calcium bentonite in the water dispersion is poor, put into the water will produce precipitation faster.
 Application Areas
- Sodium Bentonite: Because of its excellent viscosity, water absorption and swelling, sodium bentonite is often used in industries with high performance requirements, such as precision casting, metallurgical pellets, drilling mud, chemical coatings, putty powder, starch glue, catalyst carriers, seawater slurry, as well as putty powder and other industries.
- Calcium Bentonite: calcium-based bentonite is mostly used in industries with relatively low performance requirements, such as feed carriers, fertilizer granulating agent, filler, general casting, desiccant, adsorbent, sewage treatment and other industries.