Abstract: Pseudo boehmite, as the precursor of alumina, was synthesized by co-precipitation with aluminum sulfate solution and ammonia water as raw materials. Under pH 8.5-9 and pH 5-6 conditions, different pseudo boehmite samples were prepared by introducing sulfate ion, chloride ion, oxalate ion and borate ion, respectively. The main physicochemical properties of the prepared pseudo boehmite samples were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and BET specific surface area measurements. The effects of different anions on the growth of pseudo boehmite crystals and their possible mechanisms were discussed. The results show that the adsorption of anions on the crystal faces of pseudo boehmite is anisotropic, and the growth of crystal facet with the highest amount of adsorbed anions will be inhibited to some extent. The adsorption of anions on the surface of pseudo boehmite is determined by the pH of the solution: when pH of the solution is in the range of 5-6, the anions are strongly selectively adsorbed on the crystal surface; on the other hand, when pH of the solution is in the range of 8.5-9, the adsorption of anions on the crystal surface is weak, which shows that the orientation growth of anions on the crystal surface has no obvious effect on the grain morphology.

Key words: pseudo boehmite, alumina, anion, crystal face