Influences of New Synthesized Active Seeds and Industrial Seed on the Aluminum Hydroxide Precipitation from Sodium Aluminate Solution

摘要

The aluminum hydroxide precipitation process from sodium aluminate solution was studied by adding the new synthesized active seeds and industrial seed separately. The results show that the precipitation rate reached 47, 81, and 68% at 60 h by adding industrial seed, seed A, and seed B (active seeds), respectively. Specific surface area, composition, morphology, and particle size distribution of seeds/precipitated products from supersaturated sodium aluminate solutions were investigated by Brunauer, Emmett, and Teller (BET) analysis, X-ray crystallography (XRD) analysis, Scanning electron microscope (SEM) images, and Power-spectral-density (PSD) analysis. Also, to study and understand the functional groups on the surface of seed/precipitated products and precipitation mechanisms, Fourier-transform infrared spectroscopy (FTIR) analysis was recorded. The result showed that the precipitation rate of the active seeds is higher than that of the industrial seed owing to the higher surface area, more active sites, crystal defects, and finer particle size that cause rise to nucleation for gibbsite. Also, improved precipitation of aluminum hydroxide from sodium aluminate solution may be due to the predominant phase crystallized of bayerite in the composition of active seeds. The FTIR analysis shows that the decline of the precipitation process in the presence of industrial seed may be due to oxalate-Al bonds and the impurity of carbonate.