I used to own a well drilling rig although I hired a licensed driller to operate it.
We used Bentonite clay to make a surface/ecology seal around the casing for the first 18 feet to keep dirty water from following the casing down to the aquifer.
I can buy Bentonite clay in forty lb bags for about $10 each. Bentonite is also used in colon cleansing formulas. The problem is - I don't know what they do to it to make it fit to swallow? Maybe nothing - although they claim to. I'm not sure I trust taking something that attracts heavy metals, unless I have some confidence it doesn't contain any. The sales pitch for zeolite is that once trapped, the heavy metals can't come out and be reabsorbed, but even if that's so - if it is already full of junk, it may not be able to adsorb any more? So - how would you activate it? Mercury gasses off at quickly at 500 degrees but - that could be a dangerous process. Nitric acid dissolves lead and arsnic- but thats some pretty nasty stuff to have agound and now your into time and money and some potentially dangerous processes unless you have a chemistry background. Liquid Zeolite is cheap - if it works. Expensive if it doesn't.
RO