The optimox page is a good reference, but Iodine is more pinpointed to its group in the periodic system, halides. Also it doesnt tell (if), why and how Iodine excrete mercury etc from tissues.
My take on it is that every element / doing that increase metabolism, body temperature, saliva, sweat etc. will also increase the excretion of heavy metals, and minerals in general of course. Sauna, exercise, iodine; as one of the symptoms of hypothyroid is low body temperature and an inability to sweat.