Hydrothermal synthesis of hierarchical boehmite (γ-AlOOH) hollow microspheres with highly active surface

In this study, hierarchical boehmite (γ-AlOOH) hollow microspheres with highly active surface were prepared by hydrothermal synthesis. Scanning electron microscopy images showed that the hierarchical structure of the product was composed of hexagonal nanoflake units. Transmission electron microscopy images confirmed that the (010) plane was the main exposed surface of the crystal, and the ratio of the (010) plane to the total surface area of the crystal units was about 91.5%. The (010) plane of γ-AlOOH is occupied by hydroxyl groups with adsorption activity, which has a great influence on the adsorption performance of the materials. The possible mechanism of the product was proposed. Cetyltrimethylammonium bromide, which was used as the structure inducer, broke the interlayer hydrogen bonds of γ-AlOOH. As a result, the separated layers of the crystal formed thin flake-like structure units. The (010) crystal surface, which was usually caught between the lattice layers, could be exposed on the surface with this unique morphology. The N2 adsorption–desorption experiment showed that the specific surface area of the as-synthesized product was 43.5 m2 g−1. The adsorption capacity test revealed that γ-AlOOH hollow microspheres had an excellent adsorption performance, namely, the maximum adsorption capacity of the product for Congo red is 110 mg g−1.