DE and calcium bentonite clay deliver similar benefits, yet the means for doing so is very different.
DE is fossilized diatoms (single cell algae) that has been harvested from lake and sea beds and crushed to a very fine powder.
As pointed out, it's important to get FOOD GRADE DE, as there are industrial grades used in filtering applications.
Calcium bentonite clay on the other hand, is a mineral comound that is also a detoxifier. Unlike DE, there is little benefit to using it bentonite clay dry, except in lieu of baby powder to relieve diaper rash and eliminate bacteria on moist skin.
Not all calcium bentonite clays are created equally, and they are not all food grade. Adding food grade clay to food grade DE does NOT make it non-food grade.
Both are wonderful gifts from nature that solve MANY problems safely and in a non-toxic way.