Stability of titania nano-particles in different alcohols

The alcoholic suspensions of titania nano-particles were prepared using the methanol, ethanol, isopropanol and butanol as the solvents as well as triethanolamine (TEA) as an dispersant. The colloidal stability of suspensions, both in the absence as well as presence of TEA, was studied by measuring the zeta potential, sedimentation, pH and electrical conductivity of suspensions, dispersant adsorption and particles size distribution. Results showed that in the absence of TEA, the stability of the suspensions increases with the molecular size of alcohol (from methanol to butanol), while the zeta potential decreases. It was also observed that with the addition of TEA up to the optimum dosage (4 mL/L and 1.33 mL/L for isopropanolic and butanolic suspensions, respectively), the stability of isopropanolic and butanolic suspensions increases; however, its addition into the methanolic and ethanolic suspensions, even at very low concentrations in the order of 0.1 mL/L, results in the quick settling of the particles in the suspension. It was found that the mechanism of TEA action as a dispersant, in the isopropanolic and butanolic suspensions, is its protonation and then adsorption on the titania nano-particles, which yields an electrostatic and some steric stabilization mechanisms.