Novel boehmite and η-alumina nanostructures synthesized using a green ultrasonic-assisted hydrothermal method by clove extract for water treatment

In the paper, a novel three-dimensional self-assembly flower-like structure consisting of one-dimensional needle-like η-alumina as well as spherical boehmite and η-alumina nanoparticles synthesized through the green ultrasonic-assisted hydrothermal method (GUAH) is introduced. Also, the effects of clove extract and calcination of nanoparticles (NPs) at 550 °C on the properties of the NPs are studied. The results declare that the extract concentration and calcination affect the crystallinity of the NPs, and amorphous NPs are formed at a higher concentration of clove extract. Notably, the extract concentration predominantly impacts the optical properties of the NPs, yielding a wide range of bandgap energies from 2.3 to 4.7 eV. Moreover, the specific surface area of 173 to 330 m 2 /g, and 195 to 327 m 2 /g are obtained for boehmite and η-alumina NPs, respectively. Evaluating the efficiencies of the NPs in treating water containing copper ions (194 ppm) under varying pH conditions demonstrates high removal rates at short contact times (10 min) achieved by specific η-alumina NPs as a good candidate for water treatment from Cu 2+ ions.