Removing heavy metals from polluted surface water with a tannin-based flocculant agent.

Many environmental and health problems come from the presence of metals in surface water. Effectiveness of a new commercial tannin-based flocculant has been tested in order to remove Zn(2+), Ni(2+) and Cu(2+) by coagulation-flocculation process. pH has been adjusted in order to evaluate the real heavy metal removal due just to flocculant effect and not to hydroxide precipitation. At least a 75% of metal removal has been reported in every case, depending on pH value. Flocculant doses have been reported to be about 100-150 ppm.