Yield stress and zeta potential-pH behaviour of washed spherical α-Al₂O₃ particles with anionic additives: Particle...

The yield stress- and zeta potential-pH behaviour of washed spherical α-Al₂O₃ suspension with and without three typical anionic additives were characterized. The zero zeta potential or isoelectric point (IEP) of washed α-Al₂O₃ particles locates at pH∼ 9.5. With the increased dosage of the anionic additives, IEP moves to a lower pH range. The maximum yield stress of 50 wt% α-Al₂O₃ suspension decreases from 78.3 Pa to 50 Pa by about 36 % when citric acid is 0.2 dwb% (dispersant g/100 g powder). According to the simulation of the MM2 model, the type of O-H···O hydrogen bond existed in the CA molecule which results in a stable steric repulsive effect. The pH range where yield stress exists also moves to the lower pH with the addition of anionic additives. However, the addition of Diisobutylene-maleic anhydride sodium salt and Polystyrene sulphonic acid sodium salt increase the maximum yield stress because of the specific attraction force, hydrophobic attraction force and charge attraction force.