Porous PAO/PVA Microspheres for Efficient U(VI) Capture

The development of high-performance adsorbents with porous structure is very important for efficient uranium extraction from complex aqueous media. Here, porous poly (amidoxime)/poly (vinyl alcohol) (PAO/PVA) microspheres were fabricated by liquid nitrogen-assisted molding and subsequent vacuum freeze-drying procedures. The as-prepared composites with a PAO:PVA mass ratio of 4:1 have the superior adsorption capability at an optimal pH of 6. Its theoretical maximum adsorption capacity was estimated to be 330.2 mg g^-1 using the Langmuir model. It also exhibited good reusability for U(VI) uptake with a high capacity retention of more than 85% after five consecutive adsorption-desorption cycles. In simulated seawater containing competing ions, the PAO/PVA microspheres can preferentially capture U(VI), achieving the highest adsorption capacity of 5.06 mg g^-1, largest distribution coefficient of 65.71 L g^-1 and greatest removal efficiency of 77%. The mechanism of PAO/PVA for U(VI) adsorption was further studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements. It was found that the N/O donor atoms derived from amidoxime were the main binding sites for U(VI). This work may provide motivation for the rational design and construction of efficient PAO-based composites for uranium adsorption.