Effect of metallic ions on dispersibility of fine diaspore
(School of Resources Processing and Bioengineering, Central South University, Changsha 410083, China)
Abstract: Dispersion experiments were conducted to study the influence of metallic cations on the dispersibility of diaspore. The reaction mechanisms were investigated based on the analysis of zeta (ζ) potential and calculations of solution chemistry and DLVO theory. The results show that the valence of cations, instead of the cation type, plays an important role in the dispersibility of diaspore. The impact of multivalent metallic cations is greater than that of monovalent cations. In the presence of Ca2+ and Mg2+, the dispersion of diaspore doesn’t change in the range of pH value below 10. However, Ca2+ and Mg2+ may induce strong coagulation of particles when pH value is higher than 10. The adsorption of species of calcium and magnesium ions on diaspore can cause the compression of electric double layer, the decrease of the absolute value of zeta potential and the repulsion force between diaspore particles. The new IEP (isoelectric point) appeared at pH value of 11 may attribute to the adsorption of Mg(OH)2(s).
Key words: diaspore; metallic ions; dispersibility; zeta potential; DLVO theory