Recovery of Uranium in a Carbonate Solution Using Methyltrioctylammonium Carbonate as the Extractant

Abstract

The CARBEX process, proposed in 2008, is a spent nuclear fuel reprocessing method that relies on the alkaline environment of a carbonate-hydrogen peroxide system. The extraction stage is the most important step and is mainly used for the separation of nuclides. In this work, we focused on the extraction stage of the CARBEX process, using methyltrioctylammonium carbonate as an extractant to extract uranium from the carbonate solution. The effects of the concentration of uranium (0.02−0.17 mol/L) and carbonate (0.5−1.2 mol/L) in an aqueous solution, extractant concentration (0.1−0.6 mol/L), phase volume ratio (3:1−1:3), and temperature (25−60 °C) on the extraction distribution ratio were studied. The results show that the concentration of carbonate has a great influence on extraction, and the distribution ratio increases rapidly with the decrease of the concentration of carbonate in the aqueous phase. In addition, we investigated the potential of the extractant. The extractant can reach a distribution ratio of 0.78 in the presence of a high concentration (292.9 gU/L) of uranium in the aqueous solution. In the end, we deduced the extraction mechanism, and the extraction reaction equation was given.