Effect of zeta potential on properties of foamed colloidal suspension

We reveal that zeta potential has a notable effect on properties of foamed suspension, which remains poorly explored. It is demonstrated low zeta potential is beneficial for foam stability, and the experimental results show that absolute value of zeta potential of 30-40 mV is the boundary between stable foams and unstable foams. High zeta potential above 40 mV gives rise to instability of foamed colloidal suspension, owing to strong in-terparticle repulsion force that prevents particles from forming a closely packed particle network at liquid/air, interfaces. Besides, it is found that high zeta potential leads to low foamability of foamed colloidal suspension. It is also demonstrated herein that stable and uniform foams with thin and homogeneous-thickness wall without agglomerates can be prepared at the isoelectric point (IEP) using long-chain surfactant, which generates weak agglomerated particles that can be re-separated to monodisperse particles due to the steric hindrance effect of surfactant.