Efficient removal of dissolved tributyl phosphate from nitric acid solution by a membrane dispersion micro extractor

Since the evaporator accident on the Savannah River Site, 'red oil' has been considered an important safety issue in every nuclear reprocessing plant. The removal of dissolved tributyl phosphate (TBP) from nitric acid solution can directly avoid the formation of 'red oil' during the reprocessing of spent nuclear fuel. The present work proposed a novel extractor, membrane dispersion micro extractor (MDME) for the TBP removal. The effects of the continuous to dispersed phase flowrate, residence time and initial concentration of nitric acid in the aqueous phase on the removal efficiency and overall volumetric mass transfer coefficient were investigated. The dispersion performance of the studied system was also carried out. The results indicate that the concentration of TBP in the aqueous phase could be reduced below 20 mg/L within a short residence time of 75 s at the flowrate ratio of 10 for the inlet stream of TBP-0.3 mol/L HNO3-kerosene, which mimicked the real industrial system. The increase in the nitric acid concentration would lead to the higher removal efficiency. The overall volumetric mass transfer coefficient could reach 0.135 s-1-0.179 s-1, which is two or three orders of magnitude higher than that of the traditional solvent extraction equipment.

Automated summary

The study proposed a novel membrane dispersion micro extractor (MDME) for the removal of tributyl phosphate (TBP) from nitric acid solution. The results showed that the concentration of TBP in the aqueous phase could be reduced to below 20 mg/L within a short residence time of 75 s under certain conditions, mimicking the real industrial system. The overall volumetric mass transfer coefficient was found to be significantly higher compared to traditional solvent extraction equipment.