A New Route to the Synthesis of Fine-Grain Gibbsite

A fine-grain gibbsite (<20 μm) is obtained in 2 days compared with the usually reported several weeks. One of the parameters, which considerably affected the nature of the resulting aluminum hydroxide, has been the concentration of ammonia solution used to precipitate the aluminum gel together with the amount of aged sample. The dehydration sequence of this gibbsite was via χ-alumina. This is the path characteristic of gibbsites with fine grain. XRD, BET, TG, and SEM techniques were employed to characterize the solids obtained. A seeding experiment shows that the gibbsite prepared can be used in the Bayer process. Pure α-aluminas of 13 and 18 m 2 g - 1 were obtained after calcination at 1223 K for 1.30 h of the gibbsites prepared in 2 and 4 days, respectively.