A new route to the synthesis of fine-grain gibbsite

A fine-grain gibbsite (< 20 mum) is obtained in 2 days compared with the us ually reported several weeks. One of the parameters, which considerably aff ected the nature of the resulting aluminum hydroxide, has been the concentr ation of ammonia solution used to precipitate the aluminum gel together wit h the amount of aged sample. The dehydration sequence of this gibbsite was via chi -alumina. This is the path characteristic of gibbsites with fine gr ain. XRD, BET, TG, and SEM techniques were employed to characterize the sol ids obtained. A seeding experiment shows that the gibbsite prepared can be used in the Bayer process. Pure a-aluminas of 13 and 18 m(2) g(-1) were obt ained after calcination at 1223 K for 1.30 h of the gibbsites prepared in 2 and 4 days, respectively.