It's funny you mention chelation. The most common method (cheapest) of chelating some metal is with EDTA, which is such a strong bond that it makes it completely bio-unavailable. In fact, if your body was somehow able to break the bond and absorb the metal ion, EDTA would happily go along and find some other metal in your body to bind to. You literally take EDTA for lead poisoning, but it'll happily take calcium, copper and iron out of your body while doing it, it doesn't give a damn.