The influence of the
precipitating reagents and dispersants on the formation of nano-aluminum
hydroxide from sodium aluminate solution by chemical precipitation was
investigated. The influence of the dispersed seeds on the decomposi-tion process was
investigated too. The alkaline aluminate solutions were used as original
solutions with a concentration of Al
2O
3 having 14.78 g/dm
3, α
k—1.6 and127 g/dm
3, α
k—1.6.
For the precipitation processes there were used follow-ing precipitating reagents—solutions HCl, NaHCO
3 and NH
4HCO
3 with a concentration of 80 g/dm
3, dispersants—PEG 6000,
(NaPO
3)
6 and Tween 20. For the decomposition process the
dispersed seeds and factories seeds were used. Structural studies of the aluminum hydroxide particles were
carried out by means of the electron-probe microanalysis and scanning electron
microscopy, and phase composition of products was determined by means of X-ray
diffraction analysis.
Ammonium bicarbonate and Tween 20 were determined as the optimal precipitating
reagent and dispersant, correspondingly, resulting in dispersed aluminum hydroxide,
which is used as a seed in the decomposition process. It was established that
this product in form of dispersed seed considerably reduces the duration of the
decomposition process; the maximal decomposition of solution (73.9%) was
observed after injection of dispersеd aluminum hydroxide into solution. The
final aluminum hydroxide having 90% of particles less than 100 nanometers was
obtained within 7 hours of steady decreasing temperature from 70
°C to 48
°C.