Synergistic stabilization of Pickering emulsions by in situ modification of kaolinite with non ionic surfactant

摘要

Synergistic stabilization of decane/water emulsions with a combination of kaolinite and non ionic surfactant SPAN-80 is explored. Pure kaolinite being charged and very hydrophilic is a poor stabilizer of emulsions even when sufficient quantity of salt is added to screen electrical double layer interactions. However, the hydrophobicity (via. contact angle) of kaolinite can be tuned with increasing concentration of SPAN-80 leading to very stable O/W emulsions when both kaolinite and SPAN-80 are used. This is due to increase in hydrophobicity of kaolinite particles due to surfactant adsorption which enables them to get adsorbed at oil/water interface more efficiently. Adsorption of kaolinite at emulsion droplets is demonstrated through fluorescently labeled kaolinite. Emulsions phase inverted from O/W to W/O at very high concentrations of surfactant. This phase inversion is due to competitive adsorption of excess unadsorbed surfactant. Other general features such as the effect of salt, pH, oil/water ratio on emulsion formation, stability, type and droplet size has been studied.