Precipitation of Nanoscale Hydrous Alumina from Sodium Aluminate Solutions

Abstract

Sodium aluminate liquor was diluted and neutralized with water and oxalic acid in the presence of surface-active polymers polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and sodium carboxymethylcellulose (NaCMC). Dynamic light scattering experiments showed that the final precipitate had diameters between 80 – 300 nm when precipitated in the presence of PVP, and 600 – 800 nm when precipitated in the presence of NaCMC. The initial sols prepared using oxalic acid without surfactant had diameters of 200 – 300 nm. Scanning Electron Microscopy, SEM, Energy Dispersive Analysis by X-rays, EDAX, and X-ray diffraction were used for imaging, chemical and structural analysis of the final dialyzed particles. Transmission Electron Microcopy, TEM, images of the sols trapped and dried between nitrocellulose membranes showed that the initial particles were nearly spherical and bimodal in particle size. Larger particles had diameter of about 176 nm but were not pure solid alumina. A small fraction of initial particles had diameters much smaller than 176 nm. The discrepancies between initial and final precipitates indicate a complex precipitation pathway.

Study on the morphology of α-Al2O3 precursor prepared by precipitation method

“…Meanwhile, many new attempts have been done to prepare ␣-Al 2 O 3 powder, such as sol-gel, spray thermolysis and chemical precipitation [12][13][14]. Among these methods, chemical precipitation method exhibits some advantages, such as low processing temperature, high homogeneity and purity of the products and so on [15][16][17][18][19].…”