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Chemistry for Sustainable Development

2021 year, number 3

Optimization of the Technology of Extraction-Based Separation of Rare Earth and Transplutonium Elements Using a New Numerical Method for Calculating Chemical Equilibria

A. I. KOROBEINIKOV1,2, S. N. KALYAKIN2,3
1Federal State Unitary Enterprise Mining and Chemical Combine, Zheleznogorsk, Russia
2Institute of Chemistry and Chemical Technology SB RAS FRC Krasnoyarsk Science Center SB RAS, Krasnoyarsk, Russia
3Siberian Federal University, Krasnoyarsk, Russia
Keywords: mathematical modeling of chemical processes, chemical thermodynamics, extraction, rare earth elements, americium

Abstract

One of the most complicated tasks in spent nuclear fuel reprocessing is the separation of rare earth elements (REE) from transplutonium elements (TPE). This is due to the proximity of the extraction and sorption properties of REE and TPE. One of the most efficient and industrially tested methods of separating REE from TPE is extraction with tributyl phosphate in the presence of complexones. The difficulty in developing an effective technology for REE separation from TPE is that these elements are capable to form many complex compounds both in the aqueous phase and in the extractant. Moreover, almost any change in the extraction system (pH, type of salting-out agent, concentration of the target component, etc .) leads to a change of the dominant reactions and significantly changes the distribution coefficients. These features of the behaviour of the elements under consideration have led to the fact that the effective development of the technology of REE and TPE separation is practically impossible without designing a multifactor computer model of the process The formal system of equations of chemical thermodynamics (CTD) is a convenient element for presenting and processing data during modeling such systems. Relying on this postulate, we have developed a new specialized numerical method for calculating the composition of equilibrium chemical systems through the iterative solution of the formal system of CTD equations. The developed program based on this numerical method was used to optimize the technology of extraction separation of REE and americium.

DOI: 10.15372/CSD2021310