Effect of humic acid, pH and ionic strength on the sorption of Eu(III) on red earth and its solid component

Sorption and desorption of radioeuropium on red earth and its solid components to remove organic matter was studied at pH 5.3 +/- 0.1 and 4.5 +/- 0.1, and in 0.01M and 0.001M NaClO4 solutions, respectively. Eu( III) sorption showed strong pH and humic acid concentration dependency, and NaClO4 concentration independency. The sorption increased with increasing pH and amount of HA adsorbed on red earth. The sorption of Eu( III) on red earth was mainly dominated by surface complexation. Humic acid and high pH had a great tendency to immobilize the movement of Eu( III) in red earth. Sorption-desorption hysteresis of Eu( III) on red earth indicated that the sorption was irreversible.