阴离子对拟薄水铝石结晶生长的影响

以硫酸铝溶液和氨水为原料，采用共沉淀的方法合成氧化铝的前躯物拟薄水铝石。在pH为8.5～9和pH为5～6两种酸碱环境下，分别引入硫酸根离子、氯离子、草酸根离子以及硼酸根离子制备出不同拟薄水铝石样品，并借助X射线衍射、透射电子显微镜、N₂吸附-脱附等手段对其主要理化性质进行表征，探讨了不同阴离子对拟薄水铝石生长的影响及其可能的机理。研究结果表明，阴离子在拟薄水铝石各晶面上的吸附具有各向异性，被阴离子优先吸附的晶面生长受到一定程度的抑制。阴离子在拟薄水铝石表面的吸附受溶液pH的决定性影响：pH为5～6，即弱酸环境时，阴离子在晶面进行强选择性吸附，并依据选择性吸附的晶面的不同最终形成不同形貌的拟薄水铝石；反之，pH为8.5～9，即弱碱环境时，阴离子在晶面的吸附作用较弱，阴离子对晶面的导向生长作用对晶粒形貌的改变不明显。

EFFECTS OF ANIONS ON THE CRYSTAL GROWTH OF PSEUDO BOEHMITE

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.