PURIFICATION OF TAN RAI ALUMINUM HYDROXIDE WITH ACETIC ACID AND PREPARATION OF HIGH PURE NANOSIZE α-ALUMINA

Gibbsite is the most common form of aluminum hydroxide (AH) as commercial product of Bayer process. However, it usually contains some impurities such as sodium, iron, calcium, and silicon compounds that may not meet requirements for preparation of advanced materials or functional ones which need very high pure raw materials. In this paper, we present some results on the purification of commercial AH from Tan-rai alumina company (Vietnam) using dilute acetic acid solution. The removal yields of 93.19, 91.75, 100, and 86.03% are obtained for Na2O, CaO, Fe2O3, and SiO2 respectively, whereas the recovery of clean AH is almost quantitative. The clean AH is then used for preparation of high pure nanosize α-alumina via chemical processes of dissolution, precipitation ammonium aluminium carbonate hydroxide (AACH) with ammonium carbonate solution. After washing the excess reagents, the precipitate of AACH is then decomposed at elevated temperature to get high pure nanosize α-alumina. The obtained product rather regular and most of particles are not agglomerated. The laser scattering data on the prepared sample show that the particle sizes of the prepared α-alumina from 60 – 90 nm are obtained which are in good agreement with the data from XRD and morphology measurements. The α-alumina structure of the final product is confirmed by the XRD measurement data.