Diglycolamides (DGAs) are promising reagents for the separation of trivalent actinides and lanthanides from the nitric acid medium. The alkyl group attached to DGAs plays an important role in deciding the extraction and third phase formation behavior of trivalents in DGAs. To understand the role of alkyl group (varied from hexyl to dodecyl) attached to DGA, the extraction behavior of Nd­(III) from the nitric acid medium was studied in 0.2 M alkyl DGA in n-dodecane (n-DD). The organic phase obtained after extraction was subjected to dynamic light scattering (DLS) studies to explore the behavior of reverse micelles (or aggregates) formed in the organic phase. The data were compared with the self-aggregation behavior of DGAs in n-DD. The results revealed that the aggregate size and their distribution in n-DD increased with increase in the extraction of nitric acid and Nd­(III) in organic phase for all DGAs. However, at certain conditions of loading of HNO3 and Nd­(III) the organic phase underwent splitting into two phases namely “third phase” and “diluent phase medium”. The DLS studies on third phase showed that the concentration of aggregates in third phase was quite high and the average size of aggregate was significantly large. Moreover, the tendency of third phase formation increased with decrease in the chain length of alkyl group attached to DGA. These observations point out that DGAs with longer alkyl chain length would be desirable for preventing the third phase formation during the extraction of trivalent actinides and lanthanides from the nitric acid medium.

The aggregation behaviour of reverse micelles, formed during the extraction of neodymium nitrate and nitric acid, in an organic phase composed of tetra‐bis(2‐ethylhexyl) diglycolamide (TEHDGA) in n‐dodecane (n‐DD) was studied, at various temperatures. The organic phase, 0.2 M TEHDGA/n‐DD was equilibrated with aqueous solutions of nitric acid in the presence and absence of neodymium nitrate. At certain nitric acid and Nd(III) concentration in aqueous phase, the organic phase underwent splitting into two phases, with top phase known as “diluent rich phase”, the other one known as “third phase” or “metal ion rich phase”. Dynamic light scattering, attenuated total reflectance (ATR) ‐Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopic methods were employed for probing the size and distribution of aggregates present in the organic phase before and after splitting. The investigations revealed that the aggregates, formed in organic phase, interact efficiently with the extracted metal ions and these interactions increased with increase in the concentration of nitric acid and neodymium nitrate in organic phase. In addition, the interaction among the reverse micelles in third phase appear to be very strong as compared to that observed in the organic phase before third phase formation, and such strong interactions resulted in a merger and narrow distribution of reverse micelles in third phase.

No abstract