The behavior of mill tailings produced from a uranium extraction plant adapted an indigenously developed alkaline leaching-assisted process

Abstract

The potential impact of tailings with respect to uranium and its associated toxic metals in the surrounding environment is assessed by identifying their concentrations and physicochemical behavior in the tailings. Tessier's sequential extraction method was used to study the speciation of U, Co, Zn, Mn, Fe, Pb, Cr, and Cd in different geochemical fractions of the alkaline mill tailings of the Tummalapalle process plant. The study indicated that uranium and other toxic metals present in the tailings have different chemical forms. Most of the toxic elements are not readily available in an exchangeable phase; rather, they are present in the tailings in stable complex form. However, a few elements, such as Co, Pb, and Cd, showed significantly higher concentrations in the oxidizing phase. The elements present in the oxidizing phases can be labile after prolonged exposure to atmospheric conditions. U (nat.) and Fe associated with the tailings are indicated to be mostly distributed in the residual phase. Radioactive disequilibrium of 238U and 232Th series radionuclides in the ore, waste rock, and tailings were studied. Disequilibrium was mostly noticed in the 238U series radionuclides in these matrices; however, the 232Th series radionuclides showed a radioactive equilibrium between their parents and daughters.

Keywords

• sequential extraction
• speciation
• uranium
• uranium tailings