The insecticide de is designed to become are born and turn into a very fine dust. With this in mind i would be very careful with it. Pool grade I believe wouldn't do this. Wear a dust mask so you you don't breathe it.Diatomaceous earth is all silica because it's the shells of countless millions or billions of dead diatoms.
I would guess that this would be ok to use in a diatom filter.
It's an insecticide because the tiny diatoms irritate and dry out the insects, killing them; there is no added organic pesticide necessary.
My main concern would be about any unintended contaminants. For this reason I'd probably use diatomaceous earth from a pool supply place instead.
Although realistically it's probably all from the same sources anyway.