The increase in immobilization efficiency when tailings are mechanically treated may be due to specific
phenomena induced during milling such as entrapment of heavy metals into aggregates, solid diffusion of
metals into the crystalline reticulum of soil particles, the formation of newfresh surfaces onto whichheavy
metalsmay be irreversibly adsorbed aswell asmetal trans-speciation onto tailings fractions characterized
by stronger bonds and lower solubility.