Separation of lead-212 from natural thorium solution utilizing novel sulfonamide dibenzo-18-crown-6

Abstract

The extraction of lead-212 (²¹²Pb) from radioactive thorium (Th) waste is immensely important, as it serves to mitigate environmental risks associated with radioactive waste and provides a vital source for medical isotopes. To economically extract ²¹²Pb from thorium, we synthesized a novel extractant known as 2,13-disulfonyldiethylamine dibenzo-18-crown-6 (DSADB18C6). We assessed its performance in isolating Pb(II) by employing stable lead and optimizing the parameters of the extraction system. The results showcased an exceptional ability to extract Pb(II) efficiently. Within 10 minutes, using 20 mmol of DSADB18C6 and under conditions of 10 mg L⁻¹ lead concentration (HNO₃ = 0.5 mol L⁻¹), the extraction efficiency reached up to 96.1%. Even after four rounds of stripping with 0.4 mol L⁻¹ ammonium citrate, the efficiency remained at 90.2%. Moreover, the extraction stoichiometry and thermodynamics revealed that DSADB18C6 exhibited superior extraction performance compared to the commercial extractant 4′,4′′,(5′′)-di-(tert-butyldicyclohexano)-18-crown-6 (DtBuDC18C6), in line with the density functional theory (DFT) calculation result. Furthermore, we successfully separated ²¹²Pb from the thorium nitrate solution, maintaining radioactive equilibrium with its progeny. Gamma-spectroscopy confirmed a recovery yield of extraction exceeding 85.7%. This study presents a viable approach, underscoring the potential of DSADB18C6 as a promising extractant for the effective separation of ²¹²Pb from radioactive thorium sources.