Facile synthesis of monodisperse mesoporous zirconium titanium oxide microspheres with varying compositions and high surface areas for heavy metal ion sequestration

Monodisperse mesoporous zirconium titanium oxide microspheres with varying compositions (Zr content from 0 to 100%), high surface areas (up to 413 m 2/g) and well-interconnected mesopores are synthesized via a combined sol-gel self-assembly and solvothermal process. Surface areas, pore diameters, crystallinity and mesostructures of the products are controlled by changing the composition of the microspheres. The resulting mesoporous microspheres are tested as adsorbents to remove Cr (VI) anions from solution and the binary oxides show very high adsorption capacities (>25.40 mg/g, that is 0.49 mmol/g) in contrast to previously reported oxides (4.25 mg/g for TiO 2, 4.47 mg/g for α-Fe 2O 3, 5.8 mg/g for CeO 2). The maximum adsorption capacities of the mesoporous microspheres of varying compositions correlate with the amount of surface hydroxyl groups on the materials. A maximum adsorption capacity of 29.46 mg/g (0.57 mmol/g) is achieved on the microspheres containing 30% Zr due to abundant active hydroxyl groups for heavy metal ion adsorption. Owing to their integrated features (including variable compositions, high specific surface area, tunable pore size and monodisperse grain size) as well as specific acid-base surface properties, such mesoporous zirconium titanium oxide microspheres are also expected to have potential either as catalysts or catalyst supports for industrial applications.