One-pot preparation and uranyl adsorption properties of hierarchically porous zirconium titanium oxide beads using phase separation processes to vary macropore morphology

摘要

A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimetersized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H_2O beads) or liquid nitrogen (LN_2 beads). The inorganic beads obtained after calcination (550 °C in air) had surface areas of 140 and 128 m~2 g~(-1), respectively, and had varied pore architectures. The H_2O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN_2-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network.