Bentonite

Bentonite (CAS 1302-78-9), also known commercially as Gumbrin, Otaylite, and Wilkonite, is a naturally occurring smectite clay sourced primarily from volcanic ash deposits.

Where is Bentonite used?

• Water treatment: coagulant that removes suspended solids, turbidity, and contaminants from municipal and industrial effluents
• Water treatment: auxiliary for polyelectrolytes and inorganic flocculants.
• Civil engineering: slurry component in foundation drilling and tunnel boring
• Landfill liner systems where low permeability is required
• Coatings and adhesives: viscosity control, anti-sagging, and suspension stability
• Organobentonite is used as a rheology modifier in solvent-based coatings, providing structural viscosity at low shear rates.
• Agriculture: binder in granular fertilizer and animal feed pellet production
• It improves pellet integrity and reduces dust during handling and distribution.
• Foundry processes.
• Pelletizing iron powder.

Formulation notes

• At least 1% bentonite (35g per imperial gallon) is needed to make any difference in a dipping glaze.
• Bentonite slows down water penetration, so ware may not dry completely and can crack or fracture under steam pressure during firing if not temperature-dried.

Typical specification

• Bentonite powder is ≤200 mesh and hydrates fastest, suitable for drilling mud, foundry sand, and oil bleaching.
• Bentonite is classified into three main groups based on exchangeable sodium and calcium ions: sodium bentonite, mixed bentonite (sodium and calcium), and calcium bentonite.
• Bentonite granules are 0.5–3 mm and hydrate slower with less dust, preferred for cat litter and HDD applications.
• Bentonite pellets are 5–25 mm and compressed for slow, controlled hydration.
• Powdered bentonite is supplied in both sodium and calcium grades.

Regulatory status

• Bentonite meets API 13A standards.
• Bentonite is classified as feed additive E558 under the European classification code.

Frequently asked questions about Bentonite

What are the main applications of bentonite?

Bentonite is used in drilling mud, foundry processes, and pelletizing iron powder, among other applications.

What grades of bentonite are available?

Bentonite grades include soda-ash-treated fuller's earth for casting, soda-ash-treated fuller's earth for engineering, OCMA special product, and API special product.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.