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The ferron-colorimetric kinetics method, sulfate precipitates,
transmission and scanning electronic mocroscopies, x-ray
diffraction, Al-27 solution and solid state nuclear magnetic
resonance analysis were employed to study the speciations in
aluminum hydrolytic solutions. The Al polycations or polymers
present in these solutions were characterized. These polymeric
species precipitated by sulfate anion were present in the
shapes of sphere, lath and irregular morphologies. The
tetrahedron coordinated Al structure in the lath-shape
particles was identified by Al-27 solid state NMR. The Al
hydrolytic solutions were synthesized and aged at 25 C and 70
C. Distribution of the Al polymeric species in these solutions
were shown the variation at different temperatures. Samples
synthesized under higher temperature had lower degree of
hydrolysis and had a longer induction period on formation of
gibbsite. For the duration of aging at room temperature,
formation of gibbsite was caused by the decomposition of the
polymeric Al species to monomeric Al or low OH-Al polymers and
conversion to gibbsite.
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