Factorial design of experiments on the effect of surface charges on stability of aqueous colloidal ceramic suspension

The present investigation was aimed at studying the synergistic effects of different surface-active agents (SAA) on the stability of aqueous alumina suspensions. The SAA used were dibasic ammonium citrate as dispersant, albumin as binder and octanol-2 as an antifoaming agent. Stability of suspensions was assessed through measurement of the specific surface charge of the system, using the fact that the particles exhibit maximum repulsion between them at high magnitude of surface charge. The experiments were statistically designed to bring out the effect of each variable as well as the effect due to interactions. The results show that the strongest affects on stability of aqueous colloidal suspension is that of dibasic ammonium citrate and albumin. The effect of interactional parameters, though slightly favourable for increasing the stability of the suspension, is very small. Dibasic ammonium citrate and albumin, both highly negatively charged SAA, stabilise the suspension by increasing the overall surface charges of the ceramic particles which inturn increases the overall repulsive forces. On the other hand, the positive charge of octanol-2 neutralises/decreases the magnitude of negative surfaces charge and, consequently, decreases the stability of the suspension. It has been shown that factorial design of experiment approach is very helpful in defining conditions for an optimum performance in such complex systems.