Advances in Chemical and Electrochemical Oxidation of Americium

Abstract

Efficient trivalent actinides/lanthanides(Am3+/Ln3+) separation is one of the key components of advanced nuclear fuel cycle. Owing to their similar chemical behavior in condensed phase, it remains a challenge to adopt traditional liquid-liquid extraction techniques. The strategy of separating Am by oxidizing Am(Ⅲ) to its penta- and hexa-valent states has the benefit of high efficiency and large space of improvement and is attracting growing attention. The obstacle to adopt this strategy is the high oxidation potential, which impedes the efficient conversion of Am(Ⅲ) to Am(Ⅴ,Ⅵ) under mild conditions, and the low stability of high oxidation states of Am. This poses two questions to solve: (1) how to minimize the oxidation potential of Am? (2) how to stabilize Am in its high oxidation state? In this work, we surveyed the advances in the chemical and electrochemical oxidation of Am towards its separation from lanthanides. In its chemical oxidation, copper(Ⅲ) periodate was identified as a superior oxidants over bismuthate and persulfate in view of its high oxidizing power and high yield of Am(Ⅴ,Ⅵ). In its electrochemical oxidation, functionalization of electrode by appropriate ligands can significantly decrease the oxidation potential of Am and increase the overpotential of water, which circumvents the side reactions, e.g. oxidation of water. These results provide insights for the design and optimization of novel protocols for Am/Ln separation, and calls for improved understanding of the underlying mechanisms to stimulate extensive advances of efficient Am/Ln separation.

Keywords

• am
• chemical oxidation
• electrochemical oxidation