Application of solid phase extractants TEVA and TK200 for the separation of medically relevant ¹⁹⁹Au from thermal...

This study describes the separation of no-carrier-added (n.c.a.) ¹⁹⁹Au from thermal neutron irradiated natural platinum targets using two extraction chromatographic resins: TEVA containing a quaternary amine (Aliquat 336) and TK200 impregnated with trioctylphosphine oxide (TOPO, Cyanex 921). The behavior of Au, Pt, and Ir in HCl media (0.1-10 mol·L^-1 HCl) is examined through batch distribution coefficient (K_d) measurements and dynamic column experiments. For TEVA, the K_d of Au remains high across the entire HCl range (2-3·10⁴ mL·g^-1), whereas Pt shows a maximum K_d of 3.3·10⁴ mL·g^-1 at 1 mol·L^-1 HCl, decreasing at higher HCl concentration. Iridium exhibits low K_d values ((10-4.6·10² mL·g^-1), consistent with its presence as trivalent species forming weaker complexes with quaternary amines. For TK200, Au K_d ranges from 2·10⁵ to 5·10⁵ mL·g^-1, with a slight decrease at high acidity. Pt(IV) reaches a maximum K_d of 2.2·10⁴ mL·g^-1 at 1 mol·L^-1 HCl. A notable increase in Ir K_d is observed below 1 mol·L^-1 HCl, attributed to hydrolysis of iridium chloro complexes. Based on these distribution data, column separation is achieved in acidic media using 1 g of chromatographic resins. Gold is eluted using dilute HCl with thiourea. The separation factors (SF_Pt/Au) are 1.6·10⁴ for TEVA and 5.9·10⁴ for TK200, while the Pt decontamination factors are 158 and 650, respectively, with overall ¹⁹⁹Au yields of 97.6% and 94.1%. The dynamic Pt capacities at 1 mol·L^-1 HCl are 0.13 mmol·g^-1 for TEVA and 0.22 mmol·g^-1 for TK200. The developed separation schemes provide efficient methods for producing medically relevant n.c.a. ¹⁹⁹Au from irradiated platinum targets.