In a blog entry on this subject, the discussion begins with the announcement of a study testing a multi-level marketed zeolite product, Natural Cellular Defense (NCD) on autistic children. Naturally, the announcement is made by a distributor of the product!
The blog editor has this to say, "[I have] looked at the claims and looked at the structure of zeolite and looked at the smarmy background of the zeolite pushers. It's ugly, it's stupid and it's gross. Go ahead. Cure yourselves and your neighbors. [I] will believe it when they start shutting down hospitals because everyone is so healthy from taking expensive drops of cheap, powdered rock suspended in water [...]"
A Boyd Haley quote appears, which concludes that the product (NCD) "does not significantly remove mercury from an aqueous solution".