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 mum) '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.