Abstract:The settlement properties of dicalcium silicate in the concentrated  solutions (ρ(Al₂O₃)≥180 g/L) were measured with addition of different flocculants by sintering process, and then the flocculation mechanism was discussed based on the analysis of infrared spectrum, Zeta potential and contact angle. The results of settlement experiment show that no flocculation occurs with adding either flocculant A or B containing amide groups and carboxyl groups, while flocculation appears much better and the average settlement rate of slurry reaches 19.0 mm/min in the first 5min after adding flocculant C containing amide groups, carboxyl groups and hydroxamic acid groups. And the IR results indicate that R—COO⁻ in flocculant A, B or C easily forms coordination bond with Ca²⁺ in dicalcium silicate. Meanwhile dicalcium silicate absorbs 91.04% of flocculant C but about 40% of flocculant A or B during the settling process by the analysis of organic carbon content in solid, resulting in that the variations of Zeta potential, angle contact and solid surface energy of dicalcium silicate absorbing flocculant C are more than those absorbing flocculant A or B. These facts imply that more adsorption of flocculants onto dicalcium silicate favors the flocculant formation by hydrophobic interaction and bridge action instead of the charge neutralization.

Key words: dicalcium silicate; sodium aluminate solutions; sintering process; flocculation mechanism