Abstract:The aluminium hydroxide seed was activated by boiling distilled water. The effects of activated seed on decomposition ratio of seeded sodium aluminate liquor and particle size distribution were investigated. The experiments were carried out both at the agglomeration stage and the whole process. In the agglomeration stage, the decomposition ratio of sodium aluminate liquor is improved apparently with the addition of the seed activated for 0.5 h at low concentration of caustic alkali, and the effect is decreased when seed is activated for more than 0.5 h. While at higher concentration of caustic alkali, the enhancement is not evident only after the seed is activated more than 2.0 h. In the whole process, the enhancement can be observed after 10 h. It is assumed that the active sites blocked by organic impurities on the surface of original seed reappear after activation and the activity of seed is increased, which is approved by the morphology of Al(OH)3 product taken from liquor. The particle size distribution of product indicates that the size distribution of particles can also be improved if the activation time is proper.

Key words: aluminium hydroxide seed; seed activation; sodium aluminate liquor; agglomeration; particle size distribution