Bentonite is a clay made mostly of montmorillonite, but not all bentonites behave the same. The factor that changes performance the most is the dominant exchangeable cation: sodium or calcium. Choosing the wrong one can mean drilling mud with no viscosity or an oil filter that does not clarify. Here is how to tell them apart.
What is sodium bentonite?
In sodium bentonite, sodium sits between the mineral's layers. In contact with water those layers separate and the material swells several times its volume, forming gels and stable suspensions. That makes it ideal for:
- Drilling mud and engineering works.
- Seals, dam waterproofing and foundations.
- Clumping cat litter: it forms firm clumps with urine.
- Animal feed as a pellet binder.
What is calcium bentonite?
In calcium bentonite, calcium dominates. It swells much less, but keeps a large specific surface that gives it excellent adsorption: it traps impurities, pigments, moisture and unwanted compounds. That is why it is used for:
- Oil filtration, clarification and bleaching.
- Hydrocarbon and fuel purification.
- Animal feed as a mineral additive.
Comparison table
| Sodium | Calcium | |
|---|---|---|
| Swelling | Very high | Low to moderate |
| Viscosity in water | High (forms gel) | Low |
| Impurity adsorption | Good | Very high |
| Key uses | Drilling, construction, clumping litter | Oil and hydrocarbon filtration, feed |
Which one suits your process?
A practical rule: if you need the mineral to seal, add body or bind, think sodium; if you need it to clean or retain, think calcium. Animal feed uses both, plus kaolin, depending on the formulation.
Grupo Bentomex processes sodium bentonite (Probento 1000, Bentofeed, API grade) and calcium bentonite (Probento C, CXC and CX 60). Our technical team can advise you at no cost.
Particle size matters too
Besides the type, check the mesh. 200 mesh (74 microns) is the standard for drilling, filtration and feed; 60 mesh works in some oil filtration processes; and 6-30 or 20/30 granules are the right choice for cat litter.
Frequently asked questions
Can sodium and calcium bentonite be blended?
Yes, some formulations combine them to balance swelling and adsorption. Validate it with lab tests for your process.
Which bentonite is used in cat litter?
Clumping litter uses granulated sodium bentonite, because it forms firm clumps on contact with urine.
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