Activated bentonite is bentonite that has been treated chemically to improve how it performs. The word covers three different treatments. Soda activation raises swelling, acid activation makes bleaching earth, and organic treatment makes organoclay.
When a supplier offers activated bentonite, the first question is which treatment it means. The products do very different jobs.
Soda activation
Calcium bentonite swells little in water. Soda activation swaps some of the calcium in the clay for sodium by mixing the moist clay with soda ash, then ageing, drying and grinding it. The treated clay swells and gels more like natural sodium bentonite.
This is the most common form of activation in India, because much Indian bentonite is calcium or mixed bentonite. It is used for drilling, civil, litter, pelletising and foundry grades. Our article on Kutch bentonite explains where the raw clay comes from.
Acid activation
Acid activation treats calcium bentonite with sulphuric or hydrochloric acid. This opens the clay structure, increases its surface area, and makes it far better at adsorbing colour and impurities. The product is called bleaching earth or activated bleaching clay.
Refiners use it to remove colour, soaps and trace metals from edible oils, and to clean mineral and used oils. Buyers test bleaching performance on their own oil, as well as acidity, moisture, free acid and particle size.
Organic treatment
Organoclay is bentonite treated with quaternary ammonium compounds, so it swells in oil and solvents instead of water. It thickens oil-based drilling muds, paints, greases and inks. It needs much more process control than soda activation and is a specialty product. Buyers test gel strength in their own oil or solvent, along with moisture and particle size. If you need organoclay, treat it as a specialty chemical purchase and audit the plant's process and quality records, not just the clay source.
Pitfalls with soda-activated clay
- Too little soda ash gives low swelling, and too much can leave free alkali that affects some uses.
- Activation needs enough mixing, moisture and ageing time, and short cuts give uneven results.
- Poorly activated clay can lose part of its swelling during storage, so test the lot as shipped.
- Natural sodium bentonite and activated calcium bentonite can test alike on day one but behave differently in some uses.
What to ask a supplier
Ask which activation method is used, and whether polymers or other additives are added. Ask for test results on recent production lots, such as swelling index, viscosity or bleaching performance. Then test the shipped lot yourself or through an independent laboratory.
For swelling tests, see the bentonite swelling index. For drilling, read API grade bentonite.
Next step
We audit processing plants, check how activation is controlled, and have lots tested before loading. To choose the right activated grade, book a free sourcing review.