Novel approach for synthesis of boehmite nanostructures and their conversion to aluminum oxide nanostructures for remove Congo red.

A phase transfer method was developed to prepare boehmite (γ-AlOOH) nanostructures with various morphologies including nanofragments, nanorods, nanoflakes and multiply stacked nanostructures. The effect of the reaction temperature on the morphology of the as-prepared γ-AlOOH was investigated systematically. After calcination, the corresponding aluminum oxide (γ-Al2O3) nanostructures were obtained from the as-prepared γ-AlOOH products and preserving the same morphology. The obtained samples were characterized by several techniques, such as X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and N2 adsorption-desorption technique. The possible formation mechanism of the boehmites has also been proposed. Adsorption experiments indicated that γ-Al2O3 nanorods exhibited better adsorption capacity for Congo red (CR) in contrast to other as-prepared γ-Al2O3 nanostructures and commercial alumina (Al2O3), and the adsorption obeyed well to Langmuir isotherm model. Besides, the adsorption kinetics followed pseudo-second-order rate equation.