在较高N_k（铝酸钠溶液中氧化钠质量浓度,g/L）的偏铝酸钠溶液中种分得到用于晶种制备的氢氧化铝,过滤、洗涤后,在水中湿磨滤饼得到D₅₀粒度为1.0 μm左右的氢氧化铝浆液,将此浆液按最终晶种比率（晶种中氧化铝含量与溶液中氧化铝含量的比值）小于0.3%的比率,在35~42 ℃的铝酸钠溶液中分散50~70 min后,加至较低N_k、58~70 ℃的过饱和铝酸钠溶液中种分35 h左右,过滤,将滤饼洗涤、干燥、分散后得到D₅₀粒度为2.0 μm左右的氢氧化铝粉体,使用XRD、SEM对粉体进行了表征,表明粉体为三水铝石（Gibbsite）,主要晶型为伪六角块状或四角块状。还对影响产品粒度的重要条件进行了讨论。该工艺有效地解决了超细氢氧化铝生产流程中循环母液杂质累积的问题,同时具有更低的生产成本。

The aluminium hydroxide was firstly produced by the seeded precipitation process from the sodium aluminate solution with a higher Nk value（mass concentration of sodium oxide in sodium aluminate solution,g/L） for the crystal seed. After filtration and washing,the aluminium hydroxide serosity with the medium grain diameters D₅₀ of about 1.0 μm was grinded and obtained by wet ball-milling in water.The serosity subsequently was added and dispersed into a sodium aluminate solution at a temperature of 35~42 ℃ for 50~70 min,at a final crystal seed ratio of below 0.3%（the ratio of alumina contents between crystal seed and solution）.Then the new serosity was added into a sodium aluminate solution with a lower N_k value and a temperature of 58~70 ℃,after a retention time of about 35 h the sodium aluminate solution was filtered,the filter cake was washed and dried.The aluminium hydroxide powder with a particle size of about 2.0 μm was obtained.Characterization of XRD and SEM indicated that the product was gibbsite with pseudo-hexagonal or tetragonal block shape.And several important conditions of influencing the particle size were also discussed.The process solved effectively the accumulatiton problem of impurities in the aluminium hydroxide production process and had the lower production cost.