Synthesis and application study of α-Al2O3 with large specific surface area at high-temperature by hydrothermal-assisted freeze-drying

γ-AlOOH nanopowder synthesized using hydrothermal-assisted freeze-drying was employed as a precursor, with AlF₃ as a sintering aid, to explore the preparation of α-Al₂O₃ with a high specific surface area at elevated temperatures. The γ-AlOOH nanopowder produced in this study exhibited superior dispersion, achieving a specific surface area of 198.06 m 2 /g and a zeta potential of 45.8 mV. At a calcination temperature of 1200 °C, the resulting α-Al₂O₃, synthesized from γ-AlOOH and AlF₃, maintained a specific surface area of 27.72 m 2 /g, significantly higher than the typical values reported in the literature (generally below 10 m 2 /g). The α-phase purity exceeded 99 %, and the [AlO₆] proportion was 95.07 %. Furthermore, at a calcination temperature of 1150 °C, the specific surface area of the α-Al₂O₃ reached 50.48 m 2 /g. Using this α-Al₂O₃ as a carrier, a composite TiO₂ catalyst was prepared via a sol-gel and hydrothermal method. This catalyst demonstrated a photocatalytic degradation rate of over 98 % for rhodamine B (10 mg/L) within 30 min of irradiation, under the illumination of a 300 W mercury lamp in proximity to the light source.