Abstract:Na₄EDTA and EDTA were adopted as new additives to intensify the seeded precipitation process of sodium aluminate solution. The effects of the two additives at certain concentrations on the seeded precipitation rate of sodium aluminate solution, particle size distribution (PSD) and morphology of precipitated gibbsite were investigated using titration method, particle size analyzer and scanning electron microscope (SEM), respectively. The results show that the two additives can accelerate the seeded precipitation rate of sodium aluminate solution. At relatively high concentration, the facilitative effect of EDTA on sodium aluminate solution is more obvious than that of Na₄EDTA. EDTA makes gibbsite particles thinner than Na₄EDTA. The Na⁺ and H⁺ result in  the different effects on the seeded precipitation rate of sodium aluminate solution in spite of the same EDTA anion in the two additives.

Key words: sodium aluminate solution; seeded precipitation rate; Na₄EDTA; EDTA; interaction mechanism