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We did simple tests in the lab at Plainsman Clays to assess this. The makeup is simple but the method to make it is not.
*This is a popular grand of clumping cat litter. Google searches to find how cat litter is made provide disappointing results so we decided to do some simple tests.
About 50% of the material is aggregate, just particles of rock (a 50 mesh sieve caught them all). The aggregate is not water absorbent and not a ceramic grade (since it contains limestone). The role of the aggregate likely relates to the physical need of being able to pour the dry material and to provide a buffer between bentonite particles to localize sticky wet ones from dry ones (the clumping behavior).
The clay part of the material appears to be granules of pure bentonite. The swelling and colloidal behavior is distinctly like normal sodium bentonite. The degree of swelling and ability to suspend in water indicate there is likely no other clay present.
This would not be a simple material to make for mechanical reasons. Grinding machinery produces powder, it would be difficult to grind bentonite into a granule form. Normal rotary drum pelletizing processes are not likely to work (because of how sticky and impermeable it is and how resistant to drying).
Material before washing
This appears to be a mix of the bentonite and aggregate particles, likely shale and quartz. It is not clear how they are able to grind the bentonite to a granular material (it wants to be a powder). The particles do not appear to be pelletized either.
Remaining aggregate after washing
The midtone particles on the first photo appear to be the bentonite.
These particles do not appear to have significant obserbency, they are likely present in the mix to control how sticky the litter is to handle and use.
L4567 Cat Litter bentonite shard fired to cone 6.
10g water, 10g material
Swelling clearly visible, it happens immediately and takes a few minutes to turn the whole water amount into a gel.
Aggregate fired at cone 6 (2200F)
The aggregate is a refractory mix of materials since almost nothing melts when fired to 2200F (left). Some of these are clearly rehydrating on water addition after firing (right), so there is a significant percentage of limestone in the mix.
The aggregate has been removed
This is a very low specific gravity slurry yet the clay is not settling out at all even after a week. Clearly this is close to 100% sodium bentonite.
It would not be possible to dewater this on plaster so we let it evaporate, it took about 6 months, leaving only a thin layer of many super hard shards.
Cat litter fired to cone 6 - 2200F
Standard Wyoming bentonite fires to this same color and character. The high aggregate content is clearly visible. This fractured into powder after about a week.
SIEV - Sieve Analysis 35-325 Wet
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