Effect of Specific Adsorption of Ions on Electrokinetic Properties of Variable Charge Soils

Studies were carried out by using electrophoretic method on the effects of the specific adsorption of the anions, such as SO42-, PO43-, and F~ ions , the cations, such as Ca2+, Mn2+, Zn2+ and Cu2+, ions , and the anions and cations coexisting, such as Zn2+ and SO42- ions , on electrokinetic properties of the red soils as typical variable charge soils in China concerning variation in the specific ion species and concentrations , with an emphasis on the interaction between soil colloid surfaces and the ions in soil solutions. The results showed that the adsorption of specific ions led to a very pronounced decrease in zeta potentials of the soil colloids and a shift of the IEPs to lower values for specific anions, and an obvious increase in zeta potentials of the soil colloids and a shift of the IEPs to higher values for specific cations. Under circumstances of the specific anions and cations coexisting, for instance, Zn2+ and SO42- ions, the zeta potentials changed with values higher than the value for SO