On the ζ-Potential of Carbon Black Particlesin Alkaline Aqueous Solution

Abstract

The ζ-potential was measured in aqueous alkaline solutions as a part of studies of the dispersion of carbon black particles, and its origin has been discussed.The growth of the ζ-potential is connectedwith OH^- anion as a potential-determining ion, surface acidic groups (-COOH, -OH) dissociated on the particles, and quinone group reacted with cations.Also, the influence of the slipping plane in electric double layer was large on the ζ-potential.The interactions between alkali metal cations and the surface of the particles were compared with that of alkaline earth metal cations.The | ζ | -potential of the carbon black particles was greater value in aqueous solutions of alkali metal hydroxides than in that of alkaline earth metal hydroxides.The order of the influence of the cations on the ζ-potential was as following:
Cs⁺>K⁺>Na⁺>Li⁺in alkali metal cations, and
Ca²⁺>Sr²⁺>Ba²⁺ in alkaline earth metal cations.
This order of the alkali metal cations was quite contrary to that of the graphite particles in a previous study.This difference would be related to the adsorbability of the cations, the amounts of the functional groups on the surface of the particles and the free energy of hydration of the cations to both samples.