Interaction between surface active solutes and surfaces of metal oxides in polar organic solvents

Ionic surfactants are efficient as charge-controlling agents in very polar and in completely non-polar solvents. On the other hand in polar organic solvents of dielectric constants of about 25, the effect of ionic surfactants on the ζ potential is often insignificant. Weak acids can be used to control the ζ potential of TiO₂ in solvents, in which ionic surfactants are not efficient. Phosphoric acid alone and combined with bases is useful as charge-controlling agent in aliphatic alcohols and in DMSO.