http://www.custommedicine.com.au/health-articles/zeolites/
Zeolite has shown to attract mercury, cadmium, lead, arsenic and other heavy metals first because they carry a much greater positive charge than other molecules. Minerals with a lower positive charge such as calcium, sodium, potassium and magnesium have a lessor affinity.
Zeolites also have an unusual property called their ‘cation exchange’. They are able to attract and hold higher positive charged molecules and release lower positive charged particles that they may have attracted previously back into the surrounding environment. This cation exchange can be measured and varies from one zeolite to another depending on how the zeolite was originally formed.
It is negatively charged and therefore attracts and captures harmful substances with a positive charge which includes heavy metals and certain organic toxins. Zeolites travel through the body as crystal cages attracting heavy metals and other toxins like pesticides, dioxins and PCB’s just as a magnet would attract iron filings. The zeolite-toxin inclusion complex then both pass out of the body within the next 6 to 8 hours or so.
As previously mentioned Zeolites generally have a low affinity for calcium, magnesium, potassium etc and a high affinity for lead, mercury, arsenic and cadmium. Unlike other chelators, zeolites actually prefer mercury and lead to the essential minerals. The toxic minerals are structurally much smaller than the essential minerals and therefore fit better into the crystalline cage structure- they actually push the good minerals out. Atomic absorption spectroscopy studies have revealed that the selectivity of zeolite for toxic minerals is in the following order (highest attraction first):