I have tried it once about six months ago. I had just gone for a complete colonic with a therapist before that. So the effect of my home detox with Bentonite clay probably wasn't that useful to me at that point in time. I had mixed it with psyllium.
From what I've read, bentonite clay is like sponge, so it expands in water. It also is said to have a negative ionic charge, which attracts the positively charged pathogens, parasites and other toxins in the body. Once the toxins have got attached to the clay, the body gets rid of it - pathogens and all. There is no fear of it remaining inside the body, or doing any harm, as it is inert and so cannot remain trapped inside the digestive tract!