Template-free solvothermal synthesis of hierarchical boehmite hollow microspheres with strong affinity toward organic pollutants in water

Three-dimensional hierarchical boehmite hollow microspheres with a very high yield at low cost were successfully synthesized via a one-pot template-free solvothermal route using aluminum chloride hexahydrate as precursor in a mixed ethanol-water solution with assistance of trisodium citrate. The as-synthesized products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption/desorption techniques. The results show that Cl- and addition amount of trisodium citrate have significant effect on the morphologies of the resultant products, and 6-8 mmol of trisodium citrate is optimal for the synthesis of boehmite hollow microspheres assembled from randomly interconnecting and aligned nanorods with solvothermal time no less than 15 h. A synergistic mediation mechanism of citrate ions and Cl- to form boehmite hollow spheres via self-assembly morphology evolution was proposed based on the experimental results. Interestingly, the typical boehmite hollow microspheres with a surface area of 102 m(2) g(-1), pore volume of 0.37 cm(3) g(-1), and the average pore size of 14.6 nm show superb adsorption properties for Congo red with maximum capacity of 114.7 mg g(-1) which is higher than that of a commercial boehmite. This simple synthetic route is a very promising way for the design and synthesis of new functional hierarchical nanostructured materials with desired adsorptive properties. (C) 2012 Elsevier B.V. All rights reserved.