Fabrication of nano-layer-structure alumina powders from an alumina concentrate through an intensified Bayer process.

• Recovery of Al 2 O 3 from a large-scale-reserved non-bauxite resource. • An intensified Bayer process was utilized during the leaching process. • The effects of technical factors on the recovery process were discussed in details. • Fine nano-layer-structured Al 2 O 3 powders with high purity were successfully fabricated. An intensified Bayer process (high temperature, high pressure, and high alkalinity) was used to recover Al 2 O 3 to prepare nano-layer-structure Al 2 O 3 powders using Al 2 O 3 concentrate separated from large-scale pyrite tailings as the raw material. This process consisted of four main steps: pretreatment of the concentrate, leaching of the Al 2 O 3 , decomposition of the sodium aluminate solution, and sintering of the decomposed product at a high temperature. The results of the orthogonal leaching experiment revealed that the relative leaching efficiency (η R) of Al 2 O 3 reached 98.28% under the optimum conditions: T L = 280 °C, t L = 90 min, c NaOH = 9 N, and L/S = 4. The results of the kinetic analysis indicated that the leaching reactions followed the unreacted-shrinkage-nuclear-reaction model controlled by solid film diffusion. After decomposition and sintering under proper conditions, fine Al 2 O 3 powders composed of many tiny clusters with a nano-layer structure were finally prepared. The purity of the Al 2 O 3 products reached 99.23%, and all of the chemical compositions of the Al 2 O 3 products nearly met the grade I quality standard requirement in China. Additionally, TiO 2 was effectively enriched to 9.74% in the leaching residue. This study demonstrated that the concentrates with abundant reserves were an important Al 2 O 3 resource. [Display omitted]. [ABSTRACT FROM AUTHOR]