Evaluation of particle charging in non-aqueous suspensions

The stability of non-aqueous suspensions (sols) is dependent on sufficient charging of dispersed particles. Charges are created by electron, anion and proton adsorption. Sources for charged species are suspension liquids as well as dissolved ions and impurities. Zeta potential is one of the most sensitive experimentally available parameters for charging in non-aqueous suspensions. Changes in zeta potential of particles can be related to proton dissociation, acid-base adduct formation and hydrogen bonding energies (enthalpies) of suspension liquids. Moreover, it may equally well be related to proton reduction and water electrolytic dissociation potentials, as well as to Fermi energies for electron exchange. The repulsive energy model developed for aqueous electrolyte suspensions can be substantially simplified when dealing with non-aqueous suspensions. The exponential ratio between distance to repulsive maximum ensuring suspension stability and diffuse charge layer thickness can be used to evaluate the range of applicability of each model. The attractive energy may be neglected, but it is in most cases smaller but significant in comparison to repulsive energy.61