Nd(III) hypersensitive peak as an optical absorption probe for determining nitric acid in aqueous solution: An application to aqueous raffinate solutions in nuclear reprocessing

Diglycolamic acid for the mutual separation of lanthanides and actinides from dilute nitric acid solution: solvent extraction, dynamic light scattering, and spectroscopic investigations

“…The speciation of trivalent f-ions in an organic phase is essential for understanding the metal–ligand coordination chemistry in the organic phase and the driving force responsible for the extraction of metal ions. Considering the highly sensitive spectral characteristics of Nd( iii ) with respect to its coordination environment, 40–52 the Nd( iii ) ion has been chosen as the representative for the trivalent f-ions in the present study. The visible absorption spectra of Nd( iii ) recorded in nitric acid medium as well as in Nd( iii )-loaded organic phase, and the results are shown in Fig.…”

“…A typical Nd( iii ) absorption spectrum comprises several absorption bands in the wavelength region of 500–900 nm due to 4f-4f electronic transitions. 40–52 These electronic transitions occur from the ground state Russell–Saunders energy term 4 I 9/2 to the excited states such as, (A) 4 G 9/2 (500–520 nm), (B) 4 G 7/2 , 2 K 13/2 (520–540 nm), (C) 4 G 5/2 , 2 G 7/2 (560–610 nm), (D) 2 H 11/2 (615–635 nm), (E) 4 F 9/2 (660–690 nm), (F) 4 F 7/2 , 4 S 3/2 (720–770 nm), (G) 2 H 9/2 , 4 F 5/2 (770–835 nm), and (H) 4 F 3/2 (850–880 nm). These electronic transitions are clearly depicted with the corresponding absorption bands appearing in the Nd( iii ) visible spectra shown in Fig.…”

“…A small change in the geometrical symmetry of the Nd( iii ) crystal field upon coordination of a ligand in the primary coordination sphere strongly affects the intensity and nature of the hypersensitive band. 40–52 In addition, the signature of all other transitions ( i.e. , A ( 4 G 9/2 ← 4 I 9/2 ), B ( 4 G 7/2 , 2 K 13/2 ← 4 I 9/2 ), F ( 4 F 7/2 , 4 S 3/2 ← 4 I 9/2 ), G ( 2 H 9/2 , 4 F 5/2 ← 4 I 9/2 ) and H ( 4 F 3/2 ← 4 I 9/2 )) are also affected by the coordination environment to some extent, and therefore these transitions also provide significant information on the coordination chemistry of Nd( iii ) with ligands.…”

“…The speciation of trivalent f-ions in an organic phase is essential for understanding the metal-ligand coordination chemistry in the organic phase and the driving force responsible for the extraction of metal ions. Considering the highly sensitive spectral characteristics of Nd(III) with respect to its coordination environment, [40][41][42][43][44][45][46][47][48][49][50][51][52] the Fig. 8 Aggregate size distribution in the nitric acid equilibrated organic phase (0.2 M HDODGA or HD 2 DGA in 30% IDA/n-dodecane) at 298 K. The nitric acid concentration in the aqueous phase was varied from 0.001 to 3 M. Table 5 Variation in the average aggregate size (Z avg ) and FWHM of the aggregate size distribution in 0.2 M HDODGA and HD 2 DGA in 30% IDA/ndodecane with the concentration of nitric acid in the aqueous phase that is in equilibrium with the organic phase at 298 K field upon coordination of a ligand in the primary coordination sphere strongly affects the intensity and nature of the hypersensitive band.…”

“…8 Aggregate size distribution in the nitric acid equilibrated organic phase (0.2 M HDODGA or HD 2 DGA in 30% IDA/n-dodecane) at 298 K. The nitric acid concentration in the aqueous phase was varied from 0.001 to 3 M. Table 5 Variation in the average aggregate size (Z avg ) and FWHM of the aggregate size distribution in 0.2 M HDODGA and HD 2 DGA in 30% IDA/ndodecane with the concentration of nitric acid in the aqueous phase that is in equilibrium with the organic phase at 298 K field upon coordination of a ligand in the primary coordination sphere strongly affects the intensity and nature of the hypersensitive band. [40][41][42][43][44][45][46][47][48][49][50][51][52] In addition, the signature of all other transitions (i.e., A ( 4 G 9/2 ' 4 I 9/2 ), B ( 4 G 7/2 , 2 K 13/2 ' 4 I 9/2 ), F ( 4 F 7/2 , 4 S 3/2 ' 4 I 9/2 ), G ( 2 H 9/2 , 4 F 5/2 ' 4 I 9/2 ) and H ( 4 F 3/2 ' 4 I 9/2 )) are also affected by the coordination environment to some extent, and therefore these transitions also provide significant information on the coordination chemistry of Nd(III) with ligands. These observations are in good agreement with the f-f transitions of Nd(III) present in nitric acid solution reported in the literature.…”