Effect of chemical structure of monoamide resins on adsorptivity to uranium(VI) in nitric acid media

For the development of resins with selectivity for uranium(VI) in nitric acid media, some silica-supported monoamide resins with different chemical structures have been newly synthesized and the adsorptivities to U(VI) in HNO3 have been examined based on our previous results that the chemical structure of monoamide resins might largely affect their adsorptivities to U(VI). The resin consisting of N-vinyl-2-pyrrolidone was found to show relatively strong adsorptivity to U(VI) in the wide concentration range of HNO3 and little dependence on them. On the other hand, the adsorptivity to U(VI) of the resin with methylacetamide showed dependence on HNO3 concentrations such as dimethylacrylamide (DMAA) resins which were previously studied, whereas the affinity to U(VI) was smaller than those of DMAA resins. According to the probable adsorption mechanism of U(VI) onto monoamide resins that two oxygen atoms of the two amide groups coordinate to U(VI), the adsorption data suggest that the adsorptivity of monoamide resins is strongly affected by the ‘chelating effect’, namely there are some optimum numbers of the atoms participating in the chelating formation.