In this paper the technical feasibility of various adsorbents for mercury removal from contaminated waters has been studied. Adsorption isotherms of mercury ions in aqueous solution have been experimentally measured on a granular activated carbon (Aquacarb 207EA), a char, a pozzolana and a yellow tuff. The experimental evidences show that the mercury capture capacity of yellow tuff and char is of few tenths of milligrams per gram of sorbent while for the pozzolana and the activated carbon this value is of the order of 1mg/g of sorbent. Moreover, for a mercury concentration as high as 3000 microg/l the pozzolana shows the highest adsorption capacity. This result seems to be quite interesting, especially in consideration of the extremely low cost of this natural sorbent.