Role of hydrazine and hydrogen peroxide in aluminium hydroxide precipitation from sodium aluminate solution

Aluminium hydroxide precipitation from synthetic sodium aluminate solution was studied in the presence of hydrazine or hydrogen peroxide. The addition of low concentration of hydrazine is found to be effective, while higher amount of hydrogen peroxide is required to generate similar effect. XRD data confirm the product phase to be gibbsitic by nature. The scanning electron micrographs (SEM) show that agglomerated products form in the presence of hydrazine while fine discrete particles are produced with hydrogen peroxide. The probable mechanism of precipitation in the presence of hydrazine and hydrogen peroxide is also discussed.