Sorption of plutonium from low level liquid waste using nano MnO₂

Abstract

Nano-crystalline MnO₂ has been synthesized by the method of alcoholic hydrolysis of KMnO₄ and its potential as a sorbent for plutonium present in the low level liquid waste (LLW) solutions was investigated. The kinetic studies on the sorption of Pu by MnO₂ reveal the attainment of equilibrium sorption in 15 h, however 90 % of sorption could be achieved within an hour. In the studies on optimization of the solution conditions for sorption, it was observed that the sorption increases with the pH of the aqueous solution, attains the maximum value of 100 % at pH = 3 and remains constant thereafter. The sorption was found to be nearly independent of the ionic strength (0.01–1.0 M) of the aqueous solutions maintained using NaClO₄, indicating the inner sphere complexation between the Pu⁴⁺ ions and the surface sites on MnO₂. Interference studies with different fission products, viz., Cs⁺, Sr²⁺ and Nd³⁺, revealed decrease in the percentage sorption with increasing pH of the suspension indicating the competition between the metal ions. However, at the metal ion concentrations prevalent in the low level liquid waste solutions, the decrease in the Pu sorption was only marginally decreased to 90 % at pH = 3, the decrease being more in the case of Nd³⁺ than that in the case of Cs⁺. This study, therefore, shows nano-crystalline MnO₂ can be used as a sorbent for separation of Pu from LLW solutions.