Application of task specific ionic liquid for the extraction of Zirconium and Hafnium

Abstract

Tri alkyl ammonium hydrogen phthalate based ionic liquid has been explored for the efficient extraction of Zr and Hf from aqueous nitric acid solution. During mass transfer Zr formed ZrL2(NO3)+ mono positive species, which got exchanged with the single cations of the ionic liquid to maintain electrical neutrality in both phase. However, for Hf, the probable extracted species was ML(NO3)2+. The mass transfer processes were spontaneous, endothermic and driven by the entropic change in the systems. The D values for Zr were found to be more than that of the Hf due to more organophilicity of the complex. The significant changes in ligand functionalities: hydroxyl, carbonyl, –CO2 of carboxyl, –OH of carboxyl on complexation with Zr4+ were evidenced by FTIR spectra. Till 200 kGy gamma exposure, the ionic liquid was found to be rigid. No appreciable modification in ligand functionalities were evidenced by FTIR. However, up to 15% reduction in extraction performance was observed. The EDXRF spectra of the functionalized ionic liquid after processing of simulated high-level waste showed the presence of U, Zr, Fe, Mn, Rh, Ni, Zn and Y along with minute contamination of Ca and Na.