A PECULIAR MORPHOLOGY OF GIBBSITE AND NORDSTRANDITE CO-CRYSTALLIZED IN THE PRESENCE OF TARTRATE IN A STRONGLY ALKALINE ENVIRONMENT

The nature and morphology of Al(OH) 3 polymorphs obtained by precipitating Al and tartrate at pH 12.0 and at a tartrate/Al molar ratio ( R ) of 0.1 were studied by X-ray diffraction, transmission electron microscopy and electron diffraction. Co-crystallization of unusually long (up to 18 μm) ‘stick-shaped’ gibbsite with platy particles of both nordstrandite, mainly, and bayerite was observed. Face-to-face associations of plates nucleated perpendicularly on the gibbsite surfaces parallel to the c axis produced peculiar elongated ‘brush’-shaped particles. In a strongly alkaline environment the inhibiting effect of tartrate on Al(OH) 3 polymorph formation is reduced and production of co-crystallized phases with structural crystallographic similarities can be observed.