Synthesis of a novel silica-based macroporous polymer containing TODGA chelating agent and its application in the chromatographic separation of Mo(VI) and Zr(IV) from diethylenetriaminepentaacetic acid

A novel silica-based N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) chelating polymeric material (TODGA/SiO2-P) was synthesized by impregnating TODGA into similar to 50 mu m of spherical SiO2-P particles for separating Mo(VI) and Zr(IV) from a HNO3 solution containing 0.05 M diethylenetriaminepentacetic acid (DTPA) in minor actinides recovery by extraction chromatography (MAREC) process. The adsorption of TODGA/SiO2-P for Mo(VI) and Zr(IV) was investigated by examining the influence of HNO3 and DTPA concentrations. It was found that HNO3 concentration from 0.3M to 9M either with or without 0.05M DTPA had a strong effect on the adsorption of Mo(VI) and Zr(IV) towards TODGA/SiO2-P. In the absence of 0.05 M DTPA, both the adsorption of Mo(VI) and Zr(IV) decreased with an increase in the concentration of HNO3 from 0.3 M to 3 M and then gradually increased. In the presence of 0.05 M DTPA, Zr(IV) showed scarcely any adsorption towards TODGA/SiO2-P below 2M HNO3 and was gradually adsorbed from 2M to 3M HNO3 while Mo(VI) showed almost noadsorption. In excess of 3 M HNO3, the adsorption curve of Mo(VI) or Zr(IV) fully overlapped with that of the absence of 0.05 M DTPA. This resulted from the dissociation of Mo(VI) or Zr(IV) from its complex with DTPA because of full protonation of DTPA in high HNO3 concentration and the strong complexation taking place simultaneously with TODGA/SiO-P. In terms of the batch experiments, the separation of Mo(VI) and Zr(IV) from a 3 M HNO3 solution containing 0.05 M DTPA was performed by employing the TODGA/SiO2-P packed column at 50 degrees C. Molybdenum(VI) was found to leak out of the column along with 3 M HNO3. Zirconium(IV) adsorbed by TODGA/SiO2-P was effectively eluted by 0.5 M2C2O4. The recovery was 101.6% for Mo(VI) and 94.8% for Zr(IV).