The bentonite story was always a red herring. Bentonite is used all the time in BT formulations for insecticdes but it has nothing to do with weaponizing simulants or anthrax. A UN inspector found a bag of bentonite at an Iraqi insecticide site and wrongly concluded the Iraqis were using it for aerosol weaponization tests. Likely it was just being used as a standard filler.
Bentonite is useless for creating aerosols - it consists of plate like crystalline material which sticks together like glue. Silica nanopowder is the key to weaponization of anthrax. It consists of tiny (12nm diameter) amorphous, ping pong ball shaped particles. These particles coat the spores and stop them clumping together.
Good points. I am familiar with Bentonite, but despite it's ineffectiveness in this application it WAS reportedly part of the Iraqi weapons program-- even though this was probably incorrect as you point out, I'd wager that this was still the reason for the interest in screening for this compound.