Abstract:High soda content in fine alumina trihydrate(ATH) limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of electric conductivity of solution, soda content in ATH, measurement of particle size distribution and microscopic analysis. The results show that high concentration of sodium aluminate solution, ground circulative seed, low temperature or fast initial precipitation rate increases the soda content in ATH. Soda mainly exists in lattice soda and less soda in desilication product (DSP) exists in the fine ATH precipitated from sodium aluminate solution with concentration of Al₂O₃ (ρ_Al2O3) more than 160 g/L and mass ratio of alumina to silica (μ_SiO2) of 400, and lattice soda decreases with increasing initial precipitation temperature, aging seed, and low precipitation rate and precipitation time. Results also imply that ion-pair influences lattice soda content in ATH on the basis of electric conductivity variation.

Key words: alumina trihydrate; seeded precipitation; soda content; lattice soda; sodium aluminate solution