Study on Extraction Behavior of Re(VII) with Bis-triamide Extractants

In this paper, three bis-triamide extractants L1, L2 and L3 containing two tertiary amines groups and six amide groups were synthesized and the effects of contact time, HNO3 concentration, salts, different acids on the extraction behavior of Re(VII) were studied in the kerosene-HNO3 system. The results established that the extraction kinetics allow the system to reach equilibrium within 2 minutes. When HNO3 is 1.0 x 10(-2) mol/L and the concentration of L is 1.0 x 10(-2) mol/L, the D-Re of L1 and L2 for the extraction of Re(VII) are 28.9, 47.3, respectively. The increase of NaNO3 and NaClO4 concentration will lead to the decrease of D-Re, and the inhibition by NaClO4 is more significant. Among the three acid systems (HNO3, HCl, H2SO4), HNO3 had the most obvious inhibition on extraction of Re(VII) because NO3- has the largest standard Gibbs hydration energy value (Delta Gh degrees) among three anions. L3 could extract Re(VII) selectively from Re(VII)/U(VI) solution, the SFRe/U of L3 is 1.06 x 10(3) when the concentration of L3 and HNO3 are both 1.0 x 10(-2) mol/L. According to slope method and extraction capacity analysis, the extraction compound is composed of one bis-triamide molecule and one ReO4 (-) ion, and thermodynamic studies showed that the extraction reaction is an endothermic and spontaneous process.

Automated summary

In this study, three bis-triamide extractants were synthesized and their extraction behavior towards Re(VII) was investigated. It was found that HNO3 concentration significantly affected the extraction efficiency, and thermodynamic analysis indicated the reaction to be endothermic and spontaneous. Selective extraction of Re(VII) from Re(VII)/U(VI) solution was achieved using one of the extractants, demonstrating the potential application of these compounds in separation processes.