The Crystallisation of Aluminium Trihydroxide (Gibbsite) from Sodium Hydroxide Solution Onto Fine Seeds: Physico‐chemical Studies on the Internal Structure and Agglomeration of Different Crystal Fractions

A batch of Bayer gibbsite crystals (particle size range 3 to 70 μm) was prepared by crystal growth onto fine seeds (1 to 3 μm) from sodium hydroxoaluminate/sodium hydroxid‐solution. The internal structures and seed agglomeration of different fractions were examined by optical microscopy, infra‐red spectrophotometry, thermal analysis and chemical dissolution analysis. These physico‐chemical studies confirmed that crystal growth occurs with some seed agglomeration in the early stages, followed by growth onto the ‘agglomerates’. The agglomerated seeds contents ( X ) were as follows: for fraction DiD ( l 0 = 6.3 μm), X = 0.44; for fraction Gi C ( l 0 = 20 μm), X = 0.41; for fraction Gi B ( l 0 = 38 μm), X = 0.31 and for fraction Gi A ( l 0 = 55 μm), X = 0.24.