Surface Charge and Electrophoretic Mobility
of Boehmite Particles in Electrolyte Solutions

M. P. Sidorova, L. E. Ermakova, I. A. Savina, and I. A. Kavokina

Research Institute of Chemistry, St. Petersburg State University (Petrodvorets Branch),
Universitetskii pr. 2, Petrodvorets, 198904 Russia

Received June 3, 1996

Abstract—For boehmite (AlOOH) particles, dependences of surface charge and electrophoretic mobility on
the pH value and concentration of the background solution of NaCl were studied. The point of zero charge was
found to correspond to pH_PZC 9.5 and to coincide with the isoelectric point. The results were used to calculate
constants of the surface reactions and adsorption potentials of ions within the framework of the 2-pK model and
to find the capacitance of the layer that corresponds to the plane of ion pair localization. Electrophoretic mobil
ity measurements for boehmite particles in the presence of background solutions that contain ions capable of
specific adsorption (Ba²⁺, S) showed that the isoelectric point shifts toward the acidic range in Na₂SO₄
solutions; at the same time, the range of negative electrophoretic mobility is not observed in BaCl₂ solutions
within the studied pH range. This fact indicates a higher specificity of cations with respect to the boehmite sur
face in comparison with anions.

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