Structural study of lanthanides(III) in aqueous nitrate and chloride solutions by EXAFS

Structural studies of lanthanide ions (Nd(3+)similar to Lu3+: about 1 mol/l ) in the aqueous chloride (HCl: 0 similar to 6 mol/l) and nitrate\HNO3: 0 s imilar to 13 mol/l) solutions were carried out by extended X-ray absorption fine structure (EXAFS). The radial structural functions appeared to be mai nly characterized by hydration in both chloride and nitrate systems and coo rdination of nitrate ion in nitrate systems. These results indicated that n itrate ion forms inner-sphere complex with lanthanide but chloride ion hard ly forms one. The quantitative analyses of EXAFS data have revealed that th e total coordination numbers of lanthanide ranged from about 9 for light la nthanides to about 8 for heavy lanthanides in all the samples. The bond dis tances of Ln-O were from about 2.3 to 2.5 Angstrom for Ln-OH2 and from abou t 2.4 to 2.6 Angstrom for Ln-O2NO. Nitrate ion locates at 0.1 Angstrom long er position than water, it suggested that nitrate ion ligates more weakly t han water.