Variation of soda content in fine alumina trihydrate by seeded precipitation

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 (ρAl2O3) more than 160 g/L and mass ratio of alumina to silica (μSiO2) of 400, and lattice soda decreases with increasing initial precipitation temperature, aging seed, and low precipitation rate and precipitation time. Results also imply that Na+Al(OH)4− ion-pair influences lattice soda content in ATH on the basis of electric conductivity variation.