Preparation of amidoxime modified calixarene fiber for highly efficient adsorption of uranium (VI)

In this study, a novel kind of amidoxime calixarene fiber (ACF) was prepared for the first time, which was used for the adsorption of hexavalent uranium (U (VI)). The ACF was prepared by three steps, including Michael addition reaction to prepare cyano-calixarene, amidoxime reaction to prepare amidoxime calixarene, and electrospinning of ACF. The ACF was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA). These results indicated that the ACF was successfully prepared. The fibers had uniform diameter and rough surface morphology, and amidoxime was evenly distributed on the fibers surface. The comprehensive effect of pH value on Zeta potential and adsorption capacity of U (VI) was analyzed, and the adsorption kinetic and isotherm were also studied. The results showed that the solution with pH value of 7 was most suitable for the adsorption of U (VI) at 25 °C. The equilibrium adsorption capacity of ACF was 101.2 mg/g at 240 min, which maintained the desorption of 64% after five cycles. The adsorption behavior of ACF fitted the pseudo-second-order adsorption kinetic model and Langmuir adsorption isotherm model. And the intra-particle diffusion was not the only adsorption controlling mechanism during adsorption process. These results indicated that the adsorption mechanism of ACF was mainly attributed to monolayer chemical adsorption and secondary to physical adsorption. This research provides a new strategy for development the high-efficient adsorbent for uranium.