Open AccessObtaining of transition phases of alumina starting from sodium aluminate in Bayer process
Author(s) -
Zoran Obrenović,
Radislav Filipović,
Marija Milanović,
Ivan Stijepović,
Ljubiša Nikolić
Publication year - 2011
Publication title -
hemijska industrija
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.147
H-Index - 19
eISSN - 2217-7426
pISSN - 0367-598X
DOI - 10.2298/hemind110128018o
Subject(s) - gibbsite , sodium aluminate , boehmite , aluminate , bayer process , materials science , aluminium hydroxide , inorganic chemistry , chemical engineering , sodium hydroxide , aluminium , phase (matter) , fourier transform infrared spectroscopy , hydroxide , chemistry , metallurgy , organic chemistry , cement , engineering
Transition (active) phases of alumina were synthesized starting from sodium aluminate solution prepared out of Bayer liquor. The neutralisation of sodium aluminate solution was performed by sulphuric acid. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. The results show that the properties of the powders (phase composition, morphology and specific surface area) are strongly influenced by the initial pH value of the system, as well as by the duration of neutralisation step. It is possible to obtain powders with heterogeneous structure with dominant phase of bayerite, gibbsite or boehmit by tuning the pH and concentration of the starting sodium aluminate solution. The transition (active) phases of alumina (η- and γ-alumina) with high specific surface area (264-373 m2/g) are formed through the thermal dehydratation of aluminium hydroxide (bayerite and gibbsite) and aluminium oxyhydroxide (boehmite or pseudoboehmite) at the temperature of 500°C. Namely, bayerite and pseudoboehmite transforms to η-phase of alumina upon heating, while gibbsite transforms to γ-phase, maintaining the parent morphology