METHOD OF PREPARING ALUMINA

摘要

An improved method of preparing alumina, including a first stage in which an alumina hydrogel is formed from seed aluminum hydroxide, and a second stage in which the alumina hydrogel is processed for conversion into alumina. The improvemet involves the first stage comprising the steps of: (a) providing an aqueous slurry containing seed aluminum hydroxide, (b) mixing a pH controlling agent with the aqueous slurry to adjust the pH of the aqueous slurry to a value less than 5 or more than 11 and to dissolve fine crystallites of aluminum hydroxide contained in the aqueous slurry, the pH controlling agent being substantially free of ions which can form a precipitate during the first stage, and (c) then mixing an alumina compound with the aqueous slurry to adjust the pH of the aqueous slurry to a value in the range of from 6 to 11 and to cause the seed aluminum hydroxide to.grow, the steps (b) and (c) being repeated in sequence more than once so that the seed aluminum hydroxide is caused to grow into the alumina hydrogel.