Solvent extraction of thorium(IV) and rare earth elements with novel polyaramide extractant containing preorganized chelating groups

摘要

Oligoamides containing intramolecular hydrogen bonds have proved to be excellent extractants for metal cations, but their polymeric counterparts have never been used. Thorium separation from rare earth elements has long been a research subject due to its importance in nuclear energy and metallurgy. In this work a novel polyaramide has been synthesized and investigated for solvent extraction and separation of thorium and rare earths. RESULTS: The synthesized polymer 1 [(C_(32)H_(46)N_2O_6)_n], shows a high extractability of 89.4% towards Th(IV) compared with only 36-48% for rare earths. The optimized pH value for extraction of Th(IV) was 3.97. At C_1/C_M = 2.0, the extraction for Th(IV) reached 95.1%. When adding NaNO_3, the separation of Th(IV) from La(III) is more efficient than that from Eu(III) or Yb(III), especially at higher NaNO_3 concentration. Th(IV) can be thoroughly stripped from organic phase at 1.50molL~(-1) HNO_3 concentration. CONCLUSION: Direct condensation of aromatic diamine and diacid led to a novel polyaramide with introverted chelating groups. Selective extraction of Th(IV) with respect to rare earths was observed and the extraction was an endothermic process. The salting-out agent and C_1/C_M ratio can affect the separation efficiency. Thus, the polymer 1 may be a potential candidate for separating thorium and rare earths under specified conditions.