Removal of cadmium or lead from polluted water by biological amphiphiles

Biological amphiphiles were examined for the removal of Cd2+ or Pb2+ from p olluted water within a pH range from 2.5 to 7.5 at a fixed ratio of amphiph ilic concentration to heavy metal concentration (C-A/C-M) on a molar basis of approximately 11. Tannic acid, among eight amphiphiles, was selected for Cd2+ or Pb2+ removal because it exerted noticeable improvement within limi ted pH ranges. In the presence of tannic acid, the removal of Cd2+ or Pb2was investigated as a function of pH ranging from 2.5 to 13 at C-A/C-M rati os from 1.2 to 11. The removal capacity (mass of metal/mass of tannic acid) increased with decreasing C-A/C-M for both Cd2+ and Pb2+. Removal capaciti es were 0.084 and 0.154 g/g-tannic acid for Cd2+ and Pb2+ at pH 6.9 and 4.4 , respectively. The maximal removals for Cd2+ and Pb2+ were 99 and 96%, res pectively.