Effect of Magnetite Content and Specificity of Nickel(II) Ions on Electrokinetic Properties of Composites Based on Porous Silica Particles

Powders of magnetite and its composites have been obtained on the basis of macroporous high-silica glass particles containing different amounts of Fe₃O₄. XRD, XPS, and Raman spectroscopy have been employed to confirm the formation of a magnetite phase in all iron-containing samples. The surface morphology and elemental composition of porous composite particles have been studied by SEM and EDX methods. It has been found that the external surface of porous silica particles is modified to different extents. It has been shown that the position of the isoelectric point (IEP) and the values of the zeta-potentials for the composites coincide in indifferent electrolyte solutions. Two isoelectric points are observed in the pH dependences of the zeta-potential for the composite particles in nickel chloride solutions. In dilute solutions containing specifically adsorbed nickel ions and at pH below pH_IEP-2, the electrokinetic properties of the composite particles are primarily affected by magnetite phase content in a composite powder and, at rather high concentrations of Ni²⁺ ions, by their specificity with respect to oxide surfaces.