Solvent extraction of uranium(VI) by a dipicolinamide using a room-temperature ionic liquid

摘要

Room-temperature ionic liquids (RTILs) have recently received increasing attention as solvent alternatives for possible application in spent fuel reprocessing, particularly in the extraction of metal ions from high-level radioactive aqueous waste, due to their unique physical and chemical properties. Herein, the solvent extraction of the uranyl ions (UO_2~(2+)) was performed using N,N'-diethyl-N,N'-di(para)tolyl-dipicolinamide (Et_((p))TDPA) as the extractant in a commonly used ionic liquid 1-butyl-3- methylimidazolium hexafluorophosphate ([C_4mim][PF_6]). The effects of vortexing time, phase ratio and the concentration dependence of Et_((p))TDPA, nitric acid and sodium nitrate on the extraction were studied in detail. The extraction mechanism was deduced based on the slope analysis and UV-vis measurement. The distribution ratio of U from 3 mol/Lnitricacid by 0.3 mol/LEtTDPA/C_4mimPF_6 is found to be almost 100. Conventional log-log plot analysis of the extraction equilibrium data suggests that the ions are extracted as a complex in 2: 3 ratio of UO_2~(2+) to extractant, and the extractionmost likely occurs by a cationexchange mode since the concentration of C_4mim~+ in the aqueous phase increases linearly with the percent extraction of UO_2~(2+) evidenced by UV-vis measurement. This work promises to provide new efficient media based on RTILs for separation of uraniumfromthe radioactive aqueous waste.