Surface-activity of anionic–nonionic surfactants and the dispersibility of TiO₂ particles in aqueous solution

This study synthesizes the anionic–nonionic surfactants by reacting tripropylene glycol, maleic anhydride, polyoxyethylenated stearyl ether and fumaric acid. The properties of a series of anionic–nonionic surfactants that feature hydrophilic groups with different lengths of chains are measured. The critical micelle concentration (CMC) value for these surfactants decreases as the length of the polyoxyethylene chain increases. This shows that long polyoxyethylene chains promote pre-micelle formation in the aqueous phase and adsorption at the interface surrounding the aqueous phase. The dispersion of a particle suspension of ${\mathrm{\text{TiO}}}_2$ is also determined using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The results show that when anionic–nonionic surfactants are added into a ${\mathrm{\text{TiO}}}_2$ suspension, it prevents the precipitation of solid particles of ${\mathrm{\text{TiO}}}_2$ and allows greater de-aggregation of the nanoparticles. DLS data show that when the concentration of the anionic–nonionic surfactants is increased, the distribution range narrows and it becomes more uniform. The larger specific surface area of the surfactant results in greater dispersion of the suspension. The SEM results show that when anionic–nonionic surfactants feature hydrophilic groups with a shorter chain, a ${\mathrm{\text{TiO}}}_2$ suspension is more effectively dispersed.