Selective caesium transport using hollow fibre-supported liquid membrane containing calix[4]arene-bis-naphthocrown-6 as the carrier extractant

A ‘cold’ actinide partitioning run at 20 L scale with hollow fibre supported liquid membrane using diglycolamide extractants

‘Actinide partitioning’ studies were attempted by hollow fibre supported liquid membrane (HFSLM) technique using pressurized heavy water reactor simulated high level waste (PHWR-SHLW) as the feed. Two diglycolamide extractants for actinide partitioning, viz. 0.1 M TODGA (N,N,N´,N´-tetraoctyl diglycolamide) + 0.5 M DHOA (N,N-dihexyl octanamide) and 0.2 M T2EHDGA (N,N,N´,N´-tetra-2-ethylhexyl diglycolamide) + 30% iso-decanol in n-dodecane were used as the carrier solvent. Quantitative recovery of all trivalent actinides and lanthanides from PHWR-SHLW was achieved with both the carriers within 30 min when the feed volume was 0.5 L. On the other hand, about 18 h were necessary for a similar study carried out using a feed volume of 20 L. None of the other elements present in the PHWR-SHLW were transported, except small quantities of Sr and Mo. The product could be concentrated to two and four times by maintaining the feed to receiver phase volume ratio of 2:1 and 4:1, respectively. The transport behaviour of trivalent actinides and lanthanides by the two diglycolamide extractants were remarkably similar. The present studies revealed that diglycolamide-HFSLM system offers a promising alternative approach for ‘actinide partitioning’, where the use of organic solvent inventory could be drastically reduced. A mathematical model was developed and there was good agreement between the predicted and experimentally obtained data.