Board Thread:General Discussion/@comment-31283382-20161026235328/@comment-1210805-20161027023744

The Zanpakuto has the same effects on Arrancar (and by extension, presumably Menos) as on any other Hollow. It purifies or sends them to Hell. We know this because both Szayelaporro Granz and Aaroniero Arruruerie wound up in Hell after being killed in Hueco Mundo.

I believe it has been suggested (though perhaps not confirmed) that the souls devoured by a Hollow go straight into the reincarnation cycle when the Hollow is purified, and as such don't actually go to Soul Society. If this is true, then I would imagine that is what happens to the souls of Hollows killed by Kido, Fullbringers and other Hollows (when not devoured). This is better than what the Qunicy do (completely destroy the soul, thus screwing with the balance), though not as good as purifying them.