Preparation of Alumina Nanorods from Chromium-Containing Alumina Sludge

Alumina nanorods were prepared from chromium-containing alumina sludge, and the effects of doping elements, such as Cr, Fe, and Mg, were researched. The results show that the crystal transformation of alumina is restricted by the doped Cr and facilitated by the doped Fe and Mg, which is transformed from θ-Al₂O₃ to α-Al₂O₃ in the calcination process. Meanwhile, the crystal transformation of alumina is strongly restrained by co-doped elements from the chromium-containing alumina sludge. The doped elements change the course of phase structure transformation and slightly transform the chemical bond of the alumina nanorods. The impure elements are doped in the alumina crystal and restrain the crystalline growth of alumina nanorods according to the rules. In the sample prepared from chromium-containing alumina sludge, more Cr and Mg but fewer Fe are doped, and most Cr are existed as Cr(III). It is possible that the Fe-doping is confined by the competition of Cr and Mg. Moreover, the lattice imperfection of alumina is caused by doped ions, such as Cr, Fe, and Mg, and the chemical state of O and Al are affected. The findings by these experiments provide essential information for eliminating pollution and promoting comprehensive utilization of the chromium-containing alumina sludge.