N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide impregnated magnetic particles for the uptake of lanthanides and actinides from nuclear waste streams

Abstract

A novel, simple technique based on magnetically assisted chemical separation (MACS) has been developed for the uptake of lanthanides and actinides from pure nitric acid solutions as well as from Simulated Pressurized Heavy Water Reactor-High Level Waste (PHWR-SHLW). Uptake profiles of various metal ions, such as Pu(IV), U(VI), Th(IV), Am(III), Eu(III), Sr(II), Cs(I) and Fe(III) were investigated as a function of time and nitric acid concentrations using N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) impregnated magnetic particles and compared with N,N′-dimethyl-N,N′-dibutyl tetradecyl malonamide (DMDBTDMA) and trialkyl phosphine oxide coated magnetic particles and also with TODGA coated extraction chromatographic resins. The uptake of various metal ions follows the order Eu(III) > Am(III) > Th(IV) > Pu(IV) > U(VI) > Sr(II) > Fe(III) > Cs(I) in pure nitric acid solutions. On the other hand, distinctly high distribution coefficient (K d) value has been observed for Pu(IV) as compared to Eu(III) and Am(III) in SHLW. Further, no significant extraction of Cs(I) or Sr(II) was observed in SHLW. Also, at any acidity the K d value of a given metal ion is less in the SHLW as compared to that in pure HNO3, apparently due to the co-extraction of the other metal ions present in SHLW. The loading capacity of the TODGA impregnated magnetic particles with respect to Th(IV), U(VI) and Eu(III) was determined, along with the distribution isotherms to simulate multiple contacts. The adsorption models of Langmuir and Freundlich were fitted to the experimental data and best correlations was obtained for Langmuir model suggesting monolayer adsorption is the prevalent mechanism. The stability and reusability of the TODGA coated magnetic particles was also assessed.