Interaction of Electrical Double Layers Between Oppositely Charge Particles in Variable-Charge Soils as Related to Source to Salt Adsorption

摘要

The interaction of electrical double layers between oppositely charged particles of variable-charge soils collected from southern China was investigated by means Of column leaching experiments. The results showed that cations and anions of indifferent electrolytes Such as NaCl and NaNO3 were simultaneously adsorbed by some of the soils during leaching experiments. The number of the ions released was shown to be less than the number or the ions adsorbed. This probably led to the decrease in the electrical conductivity (EC) of the leachate at the initial stage of the leaching experiments. When the soil with adsorbed salt was washed with distilled water, both cations and anions adsorbed were immediately removed from the soil particle surfaces. This phenomenon is attributed to the overlapping of the diffuse layers of the electrical double layers between positively charged iron (Fe)/aluminum (Al) oxides and negatively charged phyllosilicates of the variable-charge soils. The extent of interaction between oppositely charged particles was shown to be directly related to the EC and the content of free Fc/Al oxides in the soils. The lower soil EC and higher content of soil free Fe/Al oxides appeared to cause a stronger interaction between oppositely charged particles.